Amp Deal of the Century!

[madmax]

http://www.radioshack.com/sm-accurian-homeplug-digital-audio-receiver-amplifier--pi-2049804.html

Wade through every RadioShack you can find! These cool little amps are rated at 50 watts, used to be $160 to $300 depending on when you were looking but now, they are $15 because they are totally useless without some silly ass sending unit you need to make them work as designed. The sending unit is no longer available...

So, just pop the top, remove the silly receiving board by disconnecting some cables and you end up with a very nice, smooth sounding little amplifier complete with nice torroid power supply. (just feed the signal into the "Line Out" jacks after disconnecting this board). Don't poke around in this one with power applied!

I auditioned it on a friends KEF bookshelf speakers and it sounds very sweet! I'm already looking to see what hopups could be done to it!

madmax

[WilliamM2]

If you read the reviews at RS, it seems a lot of these fail pretty quickly. But for $15...

[madmax]

Yea, they are talking about some power transistor. I will try to figure out if a particular one is getting warm before going too far. I see one that looks like it powers the add on board. Woo hoo, I love a new challenge!
madmax

[madmax]

Just picked up a pair of their bookshelf powered speakers for $30. Sweet too and almost as easy to modify. Same situation as the amps as far as no signal inputs other than AC line. I just disconnected the receiver board and hard wired the inputs. I wonder who manufactures these things for them? Very professionally done!
madmax

[gidrah]

For $15 it's a no brainer. I'll probably snag one for bi-amping.

[Polk65]

Thanks for the head's up. I picked one up last night and just popped the hood. It works and sounds pretty good. I'm thinking of using it for my computer rig or when checking out used speakers. This is easy!

(1) Remove two wiring connectors, four screws and nylon cable tie.
(2) This is what to remove.
(3) What you own.
(4) Found this on the top right corner of the board. It may be possible to find the transmitter somewhere.
(5) Two 50v 6800 uF caps.
(6) As Max says, connect your inputs to the RCA line out jacks. I'm going to change the speaker out connectors to standard jacks.
(7) Specs.

[madmax]

Its all descrete components too so if anyone wanted to replace caps, diodes transistors etc it would be very easy. Its my guess that the board we are unhooking is the same board used as the transmitter, just wired to different connectors.

A friend here at work just walked by and heard my powered speakers and was quite impressed with the sound.

madmax

[fredv]

Bought one from the local RS and have the receiver board out.
It is well worth the $15 just for the transformer itself!!
I am thinking about adding a low voltage tube to the input as a buffer :D
A 6GM8 will be a good candidate ....

[madmax]

I'm pretty sure it is a common ground amp but have not yet had a chance to remove the main pcb to look. They have me pulling double duty at work...
madmax

A tube would look real cool poking out of the case. :)

[hearingimpared]

I got mine yesterday, they said it was their last one. There are six other Rat shacks in the area, I'm gonna see if I can get another.

[fredv]

The RS shop that I went to had 5 left after I bought mine. They even joked to give me some discount if I bought them all :-)

[madmax]

I picked up the first one, liked the sound and figured at $15 you can't beat it. I picked up a few more figuring that I'm always needing an amp at my home bench to try modified stuff on and you never know when I'll want one for some special project or whatever.
madmax

Edit: Forgot, maybe one as a headphone amp. :)

[ledhed]

Well, I got one and am getting ready to remove the board. Will the volume still work or will I need a pre?

[michael_w]

Anyone found these in Canada? All the radio shacks have turned into "the Source CC" here and I can't find them online.

[fredv]

Well, I got one and am getting ready to remove the board. Will the volume still work or will I need a pre?
You don't need a pre, and the volume will work as well as the bass, treble, and balance knobs. Use the "line out" as RCA input, they share the same trace of the receiver's input to the PCB.

[ledhed]

Nope, no need for a pre. I'm sitting here listening to Boston More than a Feeling by my iPod (wanted to try something with a variable output first) using shoestring speaker wire because my good wire was too big a gauge for it. Sounds pretty good- right now I feel confident it is just as good if not better than my old Kenwood AVR which was slowly dying. Now all I need is a cheap pre amp so I can have multiple preouts.

[rskarvan]

Is it possible to... bridge this little amp... into a 100W mono-block?

[cmy330go]

Anyone having trouble getting these? I just found a local store that claims they have 5 of them. I'd be willing to pick them up and ship them for actual shipping cost.

If I do this I'll probably keep one. But that still leaves 4 for whoever.

[ledhed]

Do yours have tons of static or is it probably just all the EMF in my room?

[MillerLiteScott]

I ordered 1 today. They will call me when it comes in.

It should be great for testing rig and for a mini rig where ever.

[madmax]

None of mine have any static. Did you unhook both connectors from that board?
madmax

[rskarvan]

I'm thinking of using this for a better quality computer system speakers. Good application - I think?

[Nisqually Dave]

Hey anyone in the Tacoma Area looking for these, there are 3 in Tacoma at the 72nd st Store

7 at the Lacy Store

4 in Gig Harbor Store

3 at the Port Orchard Store

If you call one of the stores they can look up and tell you what stores have them

[ledhed]

None of mine have any static. Did you unhook both connectors from that board?
madmax

Well, the board isn't in it anymore so it can't be that :p

[fredv]

The 2 that I have don't have static either. The noise level is comparable to the t-amp. Is the static present after power on with or without any source connected?

[Polk65]

Thanks Fred. I was hoping someone with a t-amp would chime in. Can you give any other comparisons between them such as tone and power?

On the flip side of the main board the negative terminals DO share common ground. I hooked up a cd player and SDA CRS+ for an hour with volume at 10 o'clock. The amp got hot but did not fail and delivered clean sound. For S&G I turned the knob up to 11 o'clock and it was ok. At 12 o'clock the amp's relays kicked in and muted output. I quickly dialed back to 11 o'clock and the relays switched the music back on. The speakers are fine and the amp has no static.

Some mod discussion and ideas over at diyaudio http://www.diyaudio.com/forums/showthread.php?threadid=84685
and to a lesser extent at fatwallet http://www.fatwallet.com/forums/arcmessageview.php?catid=18&threadid=643263

The failures some have had I believe is due to in part to the add on board trapping heat. By removing it heat is reduced but it still gets hot. The sides of the top cover have groupings of three holes. I'm going to cut out the tabs separating them to create larger slots for more airflow. So far I've re-routed the power wires away from the audio wires. If you remove the cable tie around the blue and white wires they tuck neatly into the very top left corner.

If you see the transmitter 15-1938 grab it and take it to the bay. Three recent auctions have sold for over $100
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110114343925
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190102070160
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190106819371

[AsSiMiLaTeD]

Are these mods something anyone can do, or do I need to know about this stuff?

[AsSiMiLaTeD]

Nevermind that, I see Polk65's post above with pictures, looks to be an easy switch with no real work involved...

I'm gonna grab one of these and see how it stacks up against my TEAC...

[madmax]

Well, the board isn't in it anymore so it can't be that :p


Maybe its a wireless connection? :D

Sounds like you may have a defective unit. I'd put it back together and return it if you can't find an external reason for the noise. At work I have mine sitting on top of my PC (a VERY noisey place electrically) and am experiencing absolutely no noise.

madmax

[ledhed]

Well, it is definitely the unit. Has a hum even without being connected though the noise does not increase as the volume increases. I read that bypassing the preamp board gets rid of tons of static so I may try that eventually. Right now I'm pretty happy with it.

[gidrah]

I'm gonna grab one of these and see how it stacks up against my TEAC...

Ditto.

[adam2434]

Think I'm gonna snag one too. It looks like a nice little gadget for a portable system to take on vacations.

[Jockos]

Just got mine and pulled the board out. There is alittle hum with nothing connected. Sounds pretty good. Great little portable amp for $15!

Thanks
Jockos

[madmax]

I've been here at work all evening listening to these bookshelves and I just don't believe what they sound like!

http://www.radioshack.com/sm-homeplug-digital-receiver-speaker--pi-2104193.html

They have a cheapy 5" woofer and a cheapy soft dome tweeter but they just sound so darn good. I could listen for hours. They reproduce an acoustic bass really nice and the treble is very sweet. I've been listening to BR5-4-9 (modern bluegrass) and Michael Bloomfield (blues) and cannot get over the pleasantness and pureness of the sound. I think a lot of it has to do with the crossover. It is a simple cap crossed over at 10K with the woofer running full range. These are keepers for sure!
madmax

[Polk65]

A suggestion that you check your amp(s) carefully. Quality control could be better.

Proper use of the black wiring sleeve.
http://img403.imageshack.us/img403/6825/properxq5.jpg

This assembler forgot about the sleeve. The top of the wire doesn't look as bad as what I discovered underneath!
http://img250.imageshack.us/img250/2695/pinchedrh2.jpg

Adjustment.
http://img297.imageshack.us/img297/8030/sloppywt9.jpg

[adam2434]

I picked one up yesterday but have not had time to do the mod or power it up yet.

I did notice that the balance knob has a center position, but didn't see/feel one with the bass and treble knobs. Anyone figure out a "0" position for those yet?

[ledhed]

I think mine ended up sounding worse! There are severe EMI problems, just turning on my CDP causes an audible "pop" I'm going to remove the preamp board and see if it gets better.

[madmax]

No detent for the bass or treble. That probably saved two cents per thousand manufactured...
madmax

[cmy330go]

What is the best way to defeat or bypass the tone controls?

[madmax]

There are various levels of defeating the tone controls.
1. Use resistors to set the same resistance as the POT values when centered
2. Bypass the whole tone circuit
3. Bypass the whole preamp board.

I haven't got deep enough in it yet to give any specifics.
madmax

[cmy330go]

....I haven't got deep enough in it yet to give any specifics.
madmax

But you'll let us know when you have...right?;)

[madmax]

Oh yea, when I get time to play.
madmax

[fredv]

Try this:
1. Pull all the knobs out.
2. Open the case.
3. Unscrew the hex nuts of the control pots (use 10mm socket).
4. Disconnect the cables and wiggle slight to take the preamp board out.
5. Solder the input pin to the wiper to bypass the tone circuit.
6. Put the thing back in reverse directions.

[madmax]

That would do most of the job. The tone components would still be in place but wired around them. Probably just as good as removing them.


Hey, I found this thread. I figured we couldn't be the only people looking at this thing.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=84685

madmax

[fredv]

Thanks Fred. I was hoping someone with a t-amp would chime in. Can you give any other comparisons between them such as tone and power?

Sorry, Steve. Somehow I didn't see this post.
I only tried 2 pairs of speaker - Monitor 5 and home brew 2 way bookshelves.
In low volume (listen within 4 ft), the t-amp (battery operated) and the RS amp are quite comparable in SQ, the t-amp is more natural whereas the RS has a little more emphasis to the high and the bottom ( I supsect it was due to the tonal circuit and "not flat" settings of the bass and treble). However, the t-amp runs out of steam very quickly when cranking up the volume especially with the M5. Even though the RS amp has some coloration, it does sound more open and airy than the t-amp.

[fredv]

Try this:
5. Solder the input pin to the wiper to bypass the tone circuit.

Oops, this won't work, this is the same as turning the tone to full settings, back to reading the traces on the PCB :-)

EDIT: run a couple jumper wire from the volume control's wipers to CN3's L and R pins, maybe with resistor in between if gain is too much.

[adam2434]

How easy should it be to pop the top?

I pulling on this thing pretty hard, and it doesn't want to move. Don't want to break the case.

Am I having a "duh" moment?

[adam2434]

Screws under the rubber feet, maybe?

[fredv]

Yes, there are 5 screws, one in the center and 4 under the rubber feet.

[adam2434]

Thanks Fred, figured it out.

Hooked it up to some Infinity SS-2005 (large 3-way bookshelf, about the size of Monitor 5's) I have lying around and my son's portable DVD player.

Sounds OK, good enough for casual listening. Seemed a little harsh in the highs, but that could be the portable DVD player too. Backing off on the treble knob helped.

It was able to drive the speakers to beyond casual listening levels in the large unfinished part of my basement. The heatsink sure got toasty though.

There is a very small amount of hum with it turned up with no source connected, but really no big deal.

[adam2434]

I've been here at work all evening listening to these bookshelves and I just don't believe what they sound like!

http://www.radioshack.com/sm-homeplug-digital-receiver-speaker--pi-2104193.html

They have a cheapy 5" woofer and a cheapy soft dome tweeter but they just sound so darn good. I could listen for hours. They reproduce an acoustic bass really nice and the treble is very sweet. I've been listening to BR5-4-9 (modern bluegrass) and Michael Bloomfield (blues) and cannot get over the pleasantness and pureness of the sound. I think a lot of it has to do with the crossover. It is a simple cap crossed over at 10K with the woofer running full range. These are keepers for sure!
madmax

These are the self-amplified speakers, right? Do they have a line-level input so you can connect a standard source directly to them?

I looked at the manual and only saw speaker wire and AC connections.

Thanks

[madmax]

These are the self-amplified speakers, right? Do they have a line-level input so you can connect a standard source directly to them?

I looked at the manual and only saw speaker wire and AC connections.

Thanks

To connect a line level input you must remove the screws that hold the amplifier in then hook up wires to the connector going to the amp board. Almost as easy as the stand alone amp but not quite. For now I just have the wire hanging out but I'll drill a hole and mount a jack eventually. Well worth many times the price if you can find a pair. (Same amp and RF receiving board inside with the four knobs sticking out the front of one speaker).

[adam2434]

To connect a line level input you must remove the screws that hold the amplifier in then hook up wires to the connector going to the amp board. Almost as easy as the stand alone amp but not quite. For now I just have the wire hanging out but I'll drill a hole and mount a jack eventually. Well worth many times the price if you can find a pair. (Same amp and RF receiving board inside with the four knobs sticking out the front of one speaker).

Walked over to a local RS while my car is getting worked on today. They do have a pair - demo with one speaker having a couple scuffs.

Did you have to solder any wires for jacks?

Does the preamp stage still function - volume, balance, tone controls?

I like this as an all-in-one portable system, but am a novice at modding stuff.

Thanks

[madmax]

Did you have to solder any wires for jacks?

Does the preamp stage still function - volume, balance, tone controls?

I like this as an all-in-one portable system, but am a novice at modding stuff.

Thanks

I soldered mine but you wouldn't have to. You could just take a cheap interconnect, cut it in half and wrap the wires together and tape. Very simple stuff. I can talk you through it.
madmax

[MillerLiteScott]

Just picked up mine. I will put a screwdriver to it later tonight.


5:05 pm just made the mods to the RS amp and I was surprised by how good it sound especially for $15 bucks. I used my iPod as the source, Monitor 5's and the Monster wire that came with my SDA 2B's. Sounded great.

Plus 1 to Madmax. The hardest part of the mods was getting the little rubber feet off.

[fredv]

Just received the NOS Amperex 6GM8 tubes, they are frame grid and are very similar to the 6DJ8 family, and best of all, only costed me $4 each. Time to figure out how to squeeze in the tube and the filament transformer in the 1.6" x 4" space :-)

[adam2434]

I soldered mine but you wouldn't have to. You could just take a cheap interconnect, cut it in half and wrap the wires together and tape. Very simple stuff. I can talk you through it.
madmax

Thanks for the offer, Madmax. I'll let you know if I pick 'em up.

Do the controls work with your mod?

Also, did you just run the line level wire out the port or something?

[cmy330go]

I bought 2 last week and finally cracked one open yesterday. I must admit that I was rather shocked at how good it sounds. So good that I'm going to RS tomorrow morning to get 4 more.:D


BTW: They're not all for me.:rolleyes:

[Polk65]

Thanks Fred. I believe a t-amp would be a sideways move for me. A gainclone or glass pre may be in my future.

[madmax]

Do the controls work with your mod?

Also, did you just run the line level wire out the port or something?

Yes, all the controls work.

I just left the screws a little loose on the amp and ran the wire out through the crack for testing. At some point I'll order a jack and hook that up.
madmax

madmax

[MillerLiteScott]

I painted some white reference lines on my control knobs today. Know I know where the volume, balance, bass and treble are without question.

KISS

Sounds good.

[adam2434]

Yeah, I used a Sharpie to put a reference dot on the bass and treble knobs.

I'm going to put the RS amp with a pair of the Insignia bookshelves (that I already have and am not using) in my daughter's bedroom. Source will be a Toshiba DVD player. Won't sound half bad for about $100 total - tons better than a cheap mini system or the boombox she currently has.

Then I'll also use this for a portable system for vacations if cargo space permits.

Thanks for the heads-up on this, Madmax.

[engtaz]

Just received the NOS Amperex 6GM8 tubes, they are frame grid and are very similar to the 6DJ8 family, and best of all, only costed me $4 each. Time to figure out how to squeeze in the tube and the filament transformer in the 1.6" x 4" space :-)

Let us know how it goes. Please provide how to's and pics. Tube half sticking out the top would be neat.:D

[engtaz]

Got 1 today. Thanks for the info and I really want to know how the tube DIY project goes.

[fredv]

Let us know how it goes. Please provide how to's and pics. Tube half sticking out the top would be neat.:D
There are 2 approaches that I am considering:
1. Install the "tube board" in the place of the receiver board. That will need to
stick out an inches out from the top cover.
2. Install the "tube board" in between the preamp and the amp board - only
1.65" x 4" to work with; however, if I remove the preampboard completely,
I will have more width to work with. If I take this route, it is quite possible
that I can enclose the tubes inside the case.

This little amp seems to have a high fun factor to those want to tinker it :D

[hearingimpared]

There are 2 approaches that I am considering:
1. Install the "tube board" in the place of the receiver board. That will need to
stick out an inches out from the top cover.
2. Install the "tube board" in between the preamp and the amp board - only
1.65" x 4" to work with; however, if I remove the preampboard completely,
I will have more width to work with. If I take this route, it is quite possible
that I can enclose the tubes inside the case.

This little amp seems to have a high fun factor to those want to tinker it :D

Fred you are a true, honest-to-goodness, tinkering, audiophile. I remember when I was like that. . . 20 years ago, no arthritis, infinite patience, steady hands, gimmicks, gadgets, and junk to make and mold thing from, tools galore, and oh yeah, 50 lbs lighter!!! LOL

[fredv]

oh yeah, 50 lbs lighter!!! LOL
Joe,
Same same here, that's why I have time to tinker instead of chasing chicks :D

[hearingimpared]

Joe,
Same same here, that's why I have time to tinker instead of chasing chicks :D

WAAAAAAAAAAAAAAAA

[engtaz]

I have not worked with tubes so I have no knowledge of how to get started. Thanks for offer input.

[Polk65]

groups.google.com
google.com
alltheweb.com
altavista.com
yahoo.com

[fredv]

I have not worked with tubes so I have no knowledge of how to get started. Thanks for offer input.
Tell you the truth, I am not half as good as I seem to be with electronics :-)
You will be surprised how simple that will be when I post the final product :D

[ben62670]

Any idea if the op amps are any good in these? Just the power supply alone is worth the $15. What do you guys think the max clean voltage out from the op amps is?
Thanks Ben

[engtaz]

Tell you the truth, I am not half as good as I seem to be with electronics :-)
You will be surprised how simple that will be when I post the final product :D

I been working in electronic for over 20 years but it's all been in solidstate devices. I am not a proto type designer. Looking forward to your final product.


Thanks.
engtaz

[madmax]

I'm anxious to see what you come up with too!
madmax

[fredv]

As of now,
1. speaker connection is replaced with more friendly binding posts.
2. Input are more solid gold plate RCA jack.
3. Input wire are shielded.
4. Preamp board is gone.
5. Only a 100K pot is used in place of the preamp board.
Just the above mods, the amp is a lot quieter and neutral. I tried to bypass the preamp with the original board without much success, just too much noise.
See pic 1 for how it looks at the moment.

Since it is sort of like an amp now, I hook it up to my home brew Marantz 7c pre clone that was completed a week ago. I was totally floored. I have been listening to this combo for an hour, and I am seriously consider to leave it as it is because I doubt the 6GM8 will sound anything close to the 7c clone.
See pic2 for the junk looking 7c clone and my work bench over the floor. The
box below the 7c is a box of San Miguel, so never a dull time :-)

[engtaz]

Nice

[madmax]

I like it!
madmax

[adam2434]

Well, I got the little system set up in my 11 year-old daughter's bedroom yesterday. She loves it! Puts a smile on my face when she rocks out with it.

I ended up getting a DVD/VCR combo so she could have TV sound with the system and also plug her karaoke machine into the player's inputs, given the single input on the RS amp.

May have to find other speakers though. The Insignia's are not magnetically shielded and distort her TV, and the speakers need to flank the TV to work ideally from a space standpoint. Also, my wife was not too happy about the black speakers sitting on my daughter's white furniture next to her white TV. Got the old "you're not going to leave them there, are you" comment. So, need to try to find some inexpensive, white shielded speakers down the road. I believe RTi4's come in white, but they're a little pricey for this application.

Anyone know if the old M3's (wedge-shape) from the mid 90's are shielded?

[Polk65]

I just checked my M3's and the results on the TV were psychedelic.

[adam2434]

I just checked my M3's and the results on the TV were psychedelic.

Yeah, Polk's description didn't mention shielding either. Thanks for checking.

[madmax]

You can always find bucking magnets and glue onto your existing speakers to shield them.
madmax

[fredv]

OK, just done to switch the pre from SS to tube, turned it on, no burning smell :D At the beginning, it had a noticeable hum/buzz. After playing the wire routing game, it is almost all gone unless I put my ear right next to the speakers. Since the tube is new, it needs some time to burn in. Initial impression was - mid was a signficant improvement over the stock amp, high is less harsh; however, doesn't sound tubey - can be a common characteristics of the 6DJ8 family. Anyhow, here are a couple pictures of how the new pre fits in. The remaining task is to figure out how to install the pot properly so that I can close the case.

[engtaz]

Looking great. Now you need to teach me so I can try to do it. Thanks for all the input.

[cmy330go]

Impressive!

Do you have a schematic by chance?

[Yashu]

JBL control 1 and control 5 are shielded and come in white. The control 5s are harder to find but I understand they sound great.

The control 1 is a great budget speaker that can fit almost anywhere (even comes with wall mounts) and if you truly need bass you can get a little sub.

I would say that this amp should drive them nicely, the control 5s I would be less sure about, but the 1s would sound fine.

Any harshness in the highs that you get with this amp are just going to be magnified 1000X through the RTi4s, but the jbl's tweeter should have a sweeter sound, much better tuned for rocking out to the kinds of music kids seem to like these days.

[fredv]

Impressive!

Do you have a schematic by chance?
Yup, if it is to difficult to read, please let me know.
- B+ is the +15V
- the 6.3 heater transformer get the AC from where used to connected
to the receier board's AC.
- output's of the tube pre (pins 1 and 6) connect to the yellow and blue wires.
I used 0.1 uF/400V caps, but since the voltage is very low (12V), almost any
low voltage will do.

As of now, the gain is about 2.3, but it is still too much, I think the cathode
bypass caps can be remove to reduce the gain to something like 1.5.

The 6GM8 tube can be mounted in any position. I mount it horizontally so that I don't need to drill hole to the top.

[madmax]

It doesn't show up when I click on it.
madmax

[hearingimpared]

It doesn't show up when I click on it.
madmax

Same here!

[fredv]

I uploaded the file to http://hometown.aol.com/fvu168/rs-sch.gif
Give that a try to see you can download it. If not, I will try to post again, not sure it has anything to do with it is a gif file or now. When I select save as jpeg, stupid Photoshop created a jpeg that was 5x times as bigger than the gif!!!

The additional pot is in place now. I cut some old foam and use hot glue to glue tham in place. To my surprise, the foam melted, and guess what? It became like a mold, when all cool down, the pot was very sturdy in it's place. Last step will be cut an openning in the front of the top case, then I can all all done!!

[engtaz]

would not work with opera or internet explorer but did work with firefox. Could I bother you for a parts list including where to get the tube and socket.

Thanks for all you help and the extra work you are doing to help us out,
engtaz

[hearingimpared]

I uploaded the file to http://hometown.aol.com/fvu168/rs-sch.gif
Give that a try to see you can download it. If not, I will try to post again, not sure it has anything to do with it is a gif file or now. When I select save as jpeg, stupid Photoshop created a jpeg that was 5x times as bigger than the gif!!!

The additional pot is in place now. I cut some old foam and use hot glue to glue tham in place. To my surprise, the foam melted, and guess what? It became like a mold, when all cool down, the pot was very sturdy in it's place. Last step will be cut an openning in the front of the top case, then I can all all done!!

STill nothing there Fred!!!!

[fredv]

Good catch, I use FF and didn't know IE would render gif, sorry guys.
Try downloading it to disk, and then use Microsoft Photo Editor to open it.

I purchased the tubes from www.thetubecenter.com. Jack is a great guy to deal with, I purchased the 6GM8's along with some 5687's for an average of about $5 each shipped, and they are NOS. My 6GM8 happens to be Amperex, made in Germany!! Literally, that's the only parts that I had to purchase, I had the rest in my parts bin. Jack also has tube socket, so you can purchase one at the same time, about 2 bucks. Here are the parts list:
1. 6GM8 tube x 1 (I recommend to buy at least a couple just in case, you pay
very much same amount of shipping anyway). I bought 4, the 1st one that
I picked worked the magic right from the beginning. Since this is low voltage,
you can use it to build a computer preamp using the desktop power supply!!
2. 1 x 100 ohm resistor
3. 1 x 4700V 25V electrolytic cap (>= 2200uF 25V, I just happened to salvage this from an old computer PS :-)) #2 and #3 are to add a little more filtering to eh +15V.
4. 2 x 1200 ohm resistor (plate resistors)
5. 4 x 1M ohm resistor (anything >= 470K will work, I use 520K and 2M, ran out of 1M in my parts bin :-))
6. 2 x 180 ohm resistor (cathod resistors 180 <= antyihg <= 200 will work)
7. 2 x 47uF 25V electrolytic cap (optional, used as bypass in the cathode)
8. 2 x 0.1uF cap (coupling cap to the amp section, anything rated > 25V will do)
9. 2 x 1K resistor (grid stopper)
10. 2 x 0.01uF disk cap (>= 16V, this is to shunt the nosie from the AC to the heater).
11. 1 x 100K dual audio taper pot.
12. 1 x 117V pri, 6.3V sec tramsformer, mine is a triad rated at 0.6A in the secondary (the heater will draw 0.33A).
13. 1 x 9 pin socket.
14. 2-3 ft of shielded cable.
The rest is pretty much using whatever you can find to put everything together. If you are interested in building one, PM me you address, I will send you whatever spare parts that I find.

edit: Try this image to see it is better ....

[engtaz]

That works in opera and IE.
thanks

[madmax]

Just thought I would point out something I noticed about the Accurian. It sounds poor for the first 15 minutes or so until it warms up a bit. Anyone else notice? Although not a stretch of the imagination that warmup causes good things to happen I found it overly noticeable on this amp.
madmax

[madmax]

edit: Try this image to see it is better ....

I printed it and enlarged it but still can't read. Why is it so small?

[fredv]

I printed it and enlarged it but still can't read. Why is it so small?
Too much compression from MPE. OK, I hope 3 is a charm :-)

[fredv]

Just thought I would point out something I noticed about the Accurian. It sounds poor for the first 15 minutes or so until it warms up a bit. Anyone else notice? Although not a stretch of the imagination that warmup causes good things to happen I found it overly noticeable on this amp.
madmax

I did notice what you observed - improve after warm up, sounded a little more rich vs thin when cold. I thought it was related to the components were still new. The warm up does make sense. When the caps are fully charged, there will be more stable power supply which always translate into better sound.

[Polk65]

Looking good Fred. What's next, power transistors change?

[fredv]

Change the power transistors is a little more work now due to the molding formed around the added pot. Once the hot glued molding is ermoved, the whole tube preamp can be taken out by unscrew it from the standoff's below. Eveything is sitting on the plastic board. I bought 2 Accurian's, maybe I can mod the 2nd one's amp section to see how far it can go. Worst come to the worst, it blows, and I will reuse the toroid to build a mini aleph or gainclone :rolleyes: I will bring this amp to the BA gethering for your audition.

[engtaz]

fredv thanks,
Let us know if you have anymore tweaks. what size was your board you mounted all the components onto and what about the metal plate you have the tube on?

Question question who's got a question.
Sorry just very inquisitive about your work.

[fredv]

The transparent plastic board is about the same size as the receiving board that I removed. Maybe half inches wider and longer on each dimension, the more space the better, obviously :-) This tube can be mounted in any position, I found mounting it side was the most convenient to soldering the pins. I just happened to have such aluminum bracket from a parts out oscilloscope. You can use thick cardboard and some small right brackets to mount the cardboard vertically to the plastic board. If you can find a metal sheet, say 1.5" x 4", you can simply bend it into a right angle bracket for the tube socket. The aluminum housing that I use is indeed too big that waste a good chunk of workng space there. Also, the heat sink at the back also can be used to help securing the mounting firmly as well. As a matter of facts, I spent a lot of time to find the "right junks" and to figure out how to place them in this 4x5.5 board, and my pride I was when I pointed to the amp and told my wife, "See, those are the junk that you told me to throw away :D " Here are a few more closeup, I hope these will help.

[engtaz]

fredv,
How is it sounding to you after breakin period. Any new tweeks.

Thanks

[Polk65]

I stole two demo models yesterday at $10 each. One is going on my workbench and the other for road trips testing used speakers. Check their web page with your zip code to find which stores nearby still have them.

[madmax]

I just wanted to report in. No tweaks to mine but it has been left on since the day I got it, no problems yet.

Man, I can't wait until some time frees up so I can add a tube to mine.
madmax

[fredv]

Hi Roy,

No, I didn't tweak the amp since I put in the tube. I am using it with a pair of monitor 5's. The tube pre seems to tame the SL2000 quite a bit, the mid and the high are very smooth whereas there is not much in the bottom. I suspect the amp circuitry is designed to attenuate the lower frequency so that it can achieve the 25W rms rating. It is the stereo of the choice instead of the bigger rig when I am working from home.

It takes a little time to find and to fabricate oddities to put the transformer and tube in place. It is well worth the time. I'll bring this amp to the Bay Area Polkies gathering in June/July so that Steve can also audition and comment the difference.

[Refefer]

I stole two demo models yesterday at $10 each. One is going on my workbench and the other for road trips testing used speakers. Check their web page with your zip code to find which stores nearby still have them.

FYI, they're going for 30% off now, I scored 3 for a little over $30.

[engtaz]

Hi Roy,

No, I didn't tweak the amp since I put in the tube. I am using it with a pair of monitor 5's. The tube pre seems to tame the SL2000 quite a bit, the mid and the high are very smooth whereas there is not much in the bottom. I suspect the amp circuitry is designed to attenuate the lower frequency so that it can achieve the 25W rms rating. It is the stereo of the choice instead of the bigger rig when I am working from home.

It takes a little time to find and to fabricate oddities to put the transformer and tube in place. It is well worth the time. I'll bring this amp to the Bay Area Polkies gathering in June/July so that Steve can also audition and comment the difference.

Changing the Moniter 5's with RDO194's is a must. The sound difference is silky smooth vocals.

[fredv]

Where did you see the 30% off? The RS web still list at 14.95. The RS store nearby still has some in stock, according to their website. Maybe help them to clear all if they give me 30% off ..... Can't even buy the toroid's at this price!!!

[Refefer]

Where did you see the 30% off? The RS web still list at 14.95. The RS store nearby still has some in stock, according to their website. Maybe help them to clear all if they give me 30% off ..... Can't even buy the toroid's at this price!!!

Give them a call, and they'll look it up for you. The only RS near me that had them in stock gave me the discount at the register when I picked them up an hour or two ago.

[Polk65]

Just a reminder that if you are buying a couple of these, pop them open and have look inside. I found one with a pinched power wire and the photos are in post #35.

[Danny Tse]

How do you get the 30% off discount?

I picked up 2 of these amps this afternoon and they rang up at $14.97/each.

[Refefer]

Huh, that's strange. The store I went to said that RS was in the final stages of liquidating this stock and were giving serious discounts.

Strange.

[bundee1]

Are there any mods or tweaks to get the frequency range to 20HZ to 20KHZ?

[madmax]

Are there any mods or tweaks to get the frequency range to 20HZ to 20KHZ?

What is it now?
madmax

[hearingimpared]

Are there any mods or tweaks to get the frequency range to 20HZ to 20KHZ?

???????:confused: :confused: :confused:

[Polk65]

50Hz-20K per the manual. There is speculation that this may be bypassed in the pre stage.

8 ohm loads are good to go. 6 ohm loads will kick dust but occasionally shut it down. My next mod will be to change the power transistors.

These have become scarce in the past two weeks. Buy now if you are interested. At $15 it's a no brainer.

[aris]

sold out on the website

[cmy330go]

sold out on the website

Um.....Pretty sure they were sold out online before this thread was even started.

[madmax]

Yea, they were. Mine is still on and playing its heart out.
madmax

[fredv]

I was bored, and I took mine apart last night for the sake of "see what exactly this thing is".

I think the tranny is good for what it does, replace the output transistors tip42c/tip41c pairs will probably improve the reliability (won't burn out as easy if you accidentally crank up the volume with a low impedance speakers) won't won't give you more output power. I will say, don't touch it until it is bead ;)

Given the power supply is only a capacitor (6800uF, one per rail) after a single bridge rectifier, I am pleasantly surprised the low ripple noise!! Maybe there is some noise rejection circuit downstream, need to look at it further.

[Polk65]

Fred, keep probing. ;)

This is ~9 months after RadioShack's web site sold out. Check their product page (scroll down to 'other ways to get it') and enter local zip codes or call your local stores. http://www.radioshack.com/sm-accurian-homeplug-digital-audio-receiver-amplifier--pi-2049804.html

Chuck is tuned in. Fred is asking why. I plan on creating a gainclone from the parts, or at least a good explosion.

[fredv]

I plan on creating a gainclone from the parts, or at least a good explosion.
The tranny isn't the best fit but can be done. Let's chat more this Saturday. FWIW, I already have 2 GC channels soldered up, I just need to build a PS specific to this transformer :D

[gdpeck]

I've been here at work all evening listening to these bookshelves and I just don't believe what they sound like!

http://www.radioshack.com/sm-homeplug-digital-receiver-speaker--pi-2104193.html

They have a cheapy 5" woofer and a cheapy soft dome tweeter but they just sound so darn good. I could listen for hours. They reproduce an acoustic bass really nice and the treble is very sweet. I've been listening to BR5-4-9 (modern bluegrass) and Michael Bloomfield (blues) and cannot get over the pleasantness and pureness of the sound. I think a lot of it has to do with the crossover. It is a simple cap crossed over at 10K with the woofer running full range. These are keepers for sure!
madmax

Would these be good for a cheapy near field office system? They would be replacing some cheap cambridge soundworks 2.1 computer speakers.

[madmax]

Absolutely excellent if you could find them.
madmax

[gdpeck]

Absolutely excellent if you could find them.
madmax

OK got'em, but I'm totally confused by how to wire a line in into them. Which board is the amplifier, and where do I wire the line in?

[gdpeck]

OK got'em, but I'm totally confused by how to wire a line in into them. Which board is the amplifier, and where do I wire the line in?

OK, things look a little clearer now. I got the amp and the speakers and I can see a little better what is going on by looking at the amp board. On question though. Am I going to end up not usering the multi-speaker switch on the back of the speaker, because it looks like it is wired to the receiver board only.

[madmax]

You don't have to use it but can. It just switches left input to both channels OR right input to both channels or combined (mono) input to both. (If I recall correctly).

[ben62670]

I was bored, and I took mine apart last night for the sake of "see what exactly this thing is".

I think the tranny is good for what it does, replace the output transistors tip42c/tip41c pairs will probably improve the reliability (won't burn out as easy if you accidentally crank up the volume with a low impedance speakers) won't won't give you more output power. I will say, don't touch it until it is bead ;)

Given the power supply is only a capacitor (6800uF, one per rail) after a single bridge rectifier, I am pleasantly surprised the low ripple noise!! Maybe there is some noise rejection circuit downstream, need to look at it further.

Has anyone replaced the output transistors. I feel the best cheap upgrade would be the transistors. I have already bypassed the whole front panel with no issues of noise, DC offset, and an improvement of SQ (lower noise). There is no hiss at all with the volume bypassed:) My only complaint is the bass seems a little thin.

[ben62670]

What is the limitation of power with these. Is the weak link the PS, or the output transistors?

[Lasareath]

Somebody is selling one on ebay

http://cgi.ebay.com/Accurian-Digital-Audio-Receiver-Amplifier-15-1937-NIB_W0QQitemZ120192459525QQihZ002QQcategoryZ14980Q QssPageNameZWDVWQQrdZ1QQcmdZViewItem

Wouldn't it just be worth it to just buy a T-Amp from parts express for $30?

[ben62670]

T amp is about the same output, and does not use a toroidal type PS. I have completely removed the tone controls, and the op amps just leaving the volume, and balance. The sound improvement was well worth the trouble. I get about 103 DB c weighted on my RS SPL meter which is plenty. I just want to tighten it up a bit. SNR is good:)

[fredv]

Ben, the power supply really doesn't have enough juice, IMHO. Don't bother to replace the output transistors, not worth it. If you're itching for a new project, spend the money and time somewhere else, and that's what I am doing :-)

[ben62670]

Ben, the power supply really doesn't have enough juice, IMHO. Don't bother to replace the output transistors, not worth it. If you're itching for a new project, spend the money and time somewhere else, and that's what I am doing :-)

I have been watching some of your notes here, and at DIY:)
OK that being mentioned I was also contemplating running 2 amps. One per channel (Bi-Amping) with an active XO reserving more juice for bass. What are your thoughts? These are just computer speakers (monitor 4.6 clones) so they are only 3 feet from me.
Thanks Ben

Edit
Is the 15v DC rail good for 1 amp?

[fredv]

I have been watching some of your notes here, and at DIY:)
OK that being mentioned I was also contemplating running 2 amps. One per channel (Bi-Amping) with an active XO reserving more juice for bass. What are your thoughts? These are just computer speakers (monitor 4.6 clones) so they are only 3 feet from me.
Thanks Ben

Edit
Is the 15v DC rail good for 1 amp?
2 amp + active XO to drive a 4.6 from 3 feet away, that will be more than enough for how they are intended to use :-)
I am running only one against the M5 underneath the computer desk. The "under the desk" gain gives it a 3 dB boost for free :D Regarding to the 15V rails, it is not even close to the 1A that you want. Look at the 2 x 1.8K dropping resistors that connects to the +/- rails, you can pretty much estimate the original preamp draws approx 14ma (drops 25V). Are you planning to replace the preamp with a XO board? If so, you may want to consider to build it externally with it's own PS. It will be resusable that way as well :D

Cheers,

[ben62670]

2 amp + active XO to drive a 4.6 from 3 feet away, that will be more than enough for how they are intended to use :-)
I am running only one against the M5 underneath the computer desk. The "under the desk" gain gives it a 3 dB boost for free :D Regarding to the 15V rails, it is not even close to the 1A that you want. Look at the 2 x 1.8K dropping resistors that connects to the +/- rails, you can pretty much estimate the original preamp draws approx 14ma (drops 25V). Are you planning to replace the preamp with a XO board? If so, you may want to consider to build it externally with it's own PS. It will be resusable that way as well :D

Cheers,

You read my mind:) They are computer speakers so... I shall steal 12v from the puter for the XO. Can't get much cleaner than that. I think?

Thanks Fred

[ben62670]

Well I found some Accurian powered speakers. Of coarse I could not leave them alone. I luckily had an Accurian amp handy. I traced the circuits on the amps board, and did the same on the powered speaker's amp. Found what I was looking for. Bypassed all the crap. Op amp, tone controls, volume, and balance. Sounds better, but not as good as my Polk monitor 4.6 clones. I am very tempted to make an SDA type powered speaker. A 2 channel amp in each cabinet, 2 MW's, one tweeter, and a 12" PR. Am I retarded? Would a 12" PR on each side of a monitor look really stupid? I would have to make the cabs kinda deep. I am thinking this could be used as my Puter/bedroom system. I have the parts mostly. I think I just typed myself into it. I think I will copy and paste this in the puter speaker thread. Yes I will.

[nms]

Well I found some Accurian powered speakers. Of coarse I could not leave them alone. I luckily had an Accurian amp handy. I traced the circuits on the amps board, and did the same on the powered speaker's amp. Found what I was looking for. Bypassed all the crap. Op amp, tone controls, volume, and balance. Sounds better, but not as good as my Polk monitor 4.6 clones. I am very tempted to make an SDA type powered speaker. A 2 channel amp in each cabinet, 2 MW's, one tweeter, and a 12" PR. Am I retarded? Would a 12" PR on each side of a monitor look really stupid? I would have to make the cabs kinda deep. I am thinking this could be used as my Puter/bedroom system. I have the parts mostly. I think I just typed myself into it. I think I will copy and paste this in the puter speaker thread. Yes I will.

That was really funny reading that and watching your thought progression!! Go for it - the world can always use more Frankenpolks!

[ben62670]

I should not be encouraged
http://www.polkaudio.com/forums/showthread.php?t=53273
The voices are telling me to build again:eek:

Edit
My Shrink told to get a hobby.
Now I can't afford to see him:D

[fredv]

FWIW, Steve (polk65) built a pair from the monitor 4.6 (?) cabinet, the SDA CRS XO, and the CRS's drivers, but no 10" PR and SDA crosstalk link. I had the chance to do a home try. One Accurian was obviously under power to drive them. Also, keep in mind, SDA needs common ground, if you have each cabinet uses one amp, it may not work and can't be called SDA :-) But if you have all the parts around, then what the , I will say, go for it !!! Now here is the second voice, LOL.

[ben62670]

The speaker wiring would be a funny thing. These amps are common ground, but I would have to do some funny speaker wiring. I am thinking the Speakcon connectors. That way no matter what once wired properly it can't be screwed up. I think I would use the electronic XO, 3 amps, and for the SDA a 9.6mh between the ground, and the 200uf caps for the bass blocking duties. A little head scratching. Nothing major.

[madmax]

Just thought I would mention my amp has been powered up for use with my computer since 4-20-07 without a problem. I wonder if its burned in yet? :)
madmax

[michael_w]

I listened to one of these at the Richmond Polkfest on a pair of mini voigt pipes / tapered quarter wave lines and it was a little harsh but I'm sure with a less bright and forward speaker it would make a great combo. Awesome for $15 :D

[cmy330go]

Just thought I would mention my amp has been powered up for use with my computer since 4-20-07 without a problem. I wonder if its burned in yet? :)
madmax

Funny you should mention that. I just discovered the other day that the one I have on my garage system has been on for months and I hadn't even noticed. Still working great!

Now if I could just figure out what to do with the 5 I still have in boxes. Oh and the speakers.:rolleyes:

[apc]

Were there 'matched' speakers or do you just have some stored in the garage? I'm still looking for a set to go with my amp.

[madmax]

I listened to one of these at the Richmond Polkfest on a pair of mini voigt pipes / tapered quarter wave lines and it was a little harsh but I'm sure with a less bright and forward speaker it would make a great combo. Awesome for $15 :D
It may have still had the preamp board hooked up. Once I wired around that the harshness I heard went away. Not the perfect amp that will replace a mega-dollar one but if I had to use it all the time I wouldn't mind terribly. It does a respectable job with high eff speakers.
madmax

[madmax]

Is there a way to bridge these amps?
madmax

[michael_w]

Yes, the preamp section was still in the amp and we were running it off of USB dac going to a laptop, which in itself is a bright enough combo. Throw my Channel Islands passive in the mix and it'd probably sound great.

[Danny Tse]

Back in stock....

http://www.radioshack.com/product/index.jsp?productId=2049804

[MillerLiteScott]

I am going to pull mine off the storage shelf tomorrow and try it with a pair of RTA 8TL's that I picked up the other day.

Scott

[ben62670]

Back in stock....

http://www.radioshack.com/product/index.jsp?productId=2049804

sweet!

[madmax]

Awesome little amp. I wonder why they are back, especially at that price with no transmitter available? I bet they found a bunch of them in a warehouse somewhere.
madmax

[billbillw]

What the eff...I ordered a couple of these cheap things to play with. Probably use one for my computer instead of the T-amp that I was planning on getting. The other one will probably be used to power a set of zone-2 speakers on my screened in porch.

[madmax]

At the original price I would not have bought one but for $15 its a no brainer. They sound good.

[billbillw]

At the original price I would not have bought one but for $15 its a no brainer. They sound good.

From the website, for two amps, it works out to about $20.50 a piece w/shipping/tax...still a real steal! The current T-amp goes for $50+shipping from P.E. Two of these for less than one T-amp.

[maximillian]

Does it clip running them at reasonable levels? If that is the case, then I don't want to drive any of my "good" speakers and run the risk of blowing a tweeter.

[madmax]

It could but you would be able to hear it. Worst case amp for speaker damage is at about 100 watts per channel. This amp is maybe 30 or 50 wpc.

[ben62670]

Does it clip running them at reasonable levels? If that is the case, then I don't want to drive any of my "good" speakers and run the risk of blowing a tweeter.

No problems driving speakers at pretty high levels. A couple minor mods are in order to get surprisingly good results out of these little gems. Bypass the whole front board which ditches the lame tone controls, cheap pots, and SQ killing caps they have all over the thing. Really simple, and someone would be glad to help you through if you needed help.

Ben

[billbillw]

No problems driving speakers at pretty high levels. A couple minor mods are in order to get surprisingly good results out of these little gems. Bypass the whole front board which ditches the lame tone controls, cheap pots, and SQ killing caps they have all over the thing. Really simple, and someone would be glad to help you through if you needed help.

Ben

Assuming I would want to use this for a computer rig, what would you be using for volume control if you removed the entire tone control board? Is the range of the volume control in Windows enough to control this adequately or do you need to install a separate volume pot?

[ben62670]

Assuming I would want to use this for a computer rig, what would you be using for volume control if you removed the entire tone control board? Is the range of the volume control in Windows enough to control this adequately or do you need to install a separate volume pot?

Correct. Your sound card would be the pre. You could easily wire in a pot to control volume, but straight from the sound card works best, and a decent volume control would cost as much as the amp. I will be back in FL Tuesday, and caught up on Wednesday. If you want I will be available to Polkies to help out with the mod. I am using mine to power some custom monitors with Polk woofers, and morel tweeters. Work very good. It goes louder then you would ever want to listen to for any length of time. I even drove my RTA15rdo's with it. Bass slam wasn't there with the 4 woofers, but it did better than I expected.

[MillerLiteScott]

This little amp sounded pretty good with the Pair of RTA 8 TL's I picked up. I actually liked the mid bass clarity this combo offered. No real deep bass but more than you would expect for such a modest outlay of $.

Scott

[ben62670]

Oops

[MillerLiteScott]

No amps coming my way that I know of.

[ben62670]

No amps coming my way that I know of.

Sorry. Wrong Scott:o

[ELSock]

if i picked up a couple of these would someone mod them for me? as easy as it probably is, i'm about as delicate as a rhino... so the help would be greatly appreciated.

[ben62670]

Where do you live? I have modded 3 of these, and helped a few others. If you want to send them to me I can do the mods for you.
Ben

[MillerLiteScott]

The mods are very easy.

[ben62670]

If I remember when I get home I'll post some pics on where to attach the input wires to the main board. You can bypass a couple extra components on the main board to get the bass to go a little deeper, and clean it up very nicely in the mids, and highs.

[ELSock]

i appreciate the help, and i will most likely look into this very very soon.
and for the record, i live in Ma.

[billbillw]

My two came tonight. Definitely worth ~$20 each (w/shipping-tax).
The receiver board removal took all of 2 minutes each. Couldn't be easier really.
Not overly impressed with the sound, but they can push a pair of Mon 7B pretty loud and for their intended purpose (pushing deck speakers and/or my computer rig), they will more than suffice and for the cost, it is an absolute steal.

Oddly, the balance adjustment is backwards on both amps. They are a little noisy too. Hearing slight buzz through one or both channels on each amp. With the one I'm listening to now, the buzz seems to be diminishing the longer I have it on though.

[MillerLiteScott]

Mine does not have any buzz and I just put the speaker wire into the opposite speaker output to correct the Left/Right issue. Besides it was only $15.

Scott

[ben62670]

1.) Remove the daughter board.
2.) On the front board with the knobs remove the wires that lead to the inputs.
3.) Remove the wires that run from the front board to the main board.
4.) cut the wires from the RCA jacks near the front panel connector.
5.) Locate the input wires on the main board. They should be L G R. They are on the right side of the group of wires.
6.) Tie the input wires from the RCA's directly to the input wires on the main board.

This mod bypasses all the knobs, op-amps, resistors, and low quality caps that kill the SQ on these little amps. You will have no volume control with this mod. Your source will need variable outs. Such as an Ipod, computer, or a CD player with variable outs.

[ben62670]

My two came tonight. Definitely worth ~$20 each (w/shipping-tax).
The receiver board removal took all of 2 minutes each. Couldn't be easier really.
Not overly impressed with the sound, but they can push a pair of Mon 7B pretty loud and for their intended purpose (pushing deck speakers and/or my computer rig), they will more than suffice and for the cost, it is an absolute steal.

Oddly, the balance adjustment is backwards on both amps. They are a little noisy too. Hearing slight buzz through one or both channels on each amp. With the one I'm listening to now, the buzz seems to be diminishing the longer I have it on though.

You can loosen, and rotate the toridal transformer till the buzz goes away;)

[billbillw]

You can loosen, and rotate the toridal transformer till the buzz goes away;)

Actually, most, if not all the buzz is gone in the one that I am listening to this evening. I'll probably use that one as is for a few weeks, then dig into it further to do some mods. For the one that I'm going to use on my deck, I will leave it stock because I'll need the volume control out there. Its hard to be critical of sound in that type of environment anyway.

[pmlewis]

I just got mine yesterday. The mod was very quick and easy. The hardest part was getting the feet off the case. I have not had time to put it to use yet but I have one question. How come we can use the outputs as inputs without switching around any cables for the RCA outs? I am not very well versed on amp design/theory and was just wondering why it worked.

[billbillw]

I just got mine yesterday. The mod was very quick and easy. The hardest part was getting the feet off the case. I have not had time to put it to use yet but I have one question. How come we can use the outputs as inputs without switching around any cables for the RCA outs? I am not very well versed on amp design/theory and was just wondering why it worked.

Because the original wireless input and the line out shared a common trace on the tone board. Once the wireless board's signal is removed, the line out feeds back through the tone board just like the wireless board's input did.

[billbillw]

1.) Remove the daughter board.
2.) On the front board with the knobs remove the wires that lead to the inputs.
3.) Remove the wires that run from the front board to the main board.
4.) cut the wires from the RCA jacks near the front panel connector.
5.) Locate the input wires on the main board. They should be L G R. They are on the right side of the group of wires.
6.) Tie the input wires from the RCA's directly to the input wires on the main board.

This mod bypasses all the knobs, op-amps, resistors, and low quality caps that kill the SQ on these little amps. You will have no volume control with this mod. Your source will need variable outs. Such as an Ipod, computer, or a CD player with variable outs.

I had an idea after pmlewis asked about the wiring that allows us to use the line out for input.

I wanted to bypass the tone circuit, but I didn't want it to be permanent.
Why not hook the input wires that lead to the main board to the spot where the receiver board was hooked. These plugs all have the same pin diameter and they can be removed from the their plug and rearranged however you like. So this is what I did.
http://i45.photobucket.com/albums/f94/billbillw/Accurian002.jpg
I took the three wires that corresponded to the L/G/R feed out of the larger plug. This can be done easily by using a small pin or paperclip to press on the retaining clip and easily pull them out of the plug.
Next, I took the spare jumper wire that came off the receiver board and removed one of the plug ends. I re-inserted the 3 pins into the empty plug and then inserted it into the spot where the receiver used to plug in. Since the input and line out shared a common trace, this effectively acts as a jumper to bypass the tone controls, volume controls, etc. No cutting, no soldering, no taping. Oh yeah. I also took the sleeve off of the spare wire and put it onto the input wires to make things look cleaner.

All done in about 10 minutes. Taking the tone control out removed any hum/buzz that was coming through the amp. Something in that circuit must have been picking up the transformer's magnetic field and turning it into ripple in the output.

http://i45.photobucket.com/albums/f94/billbillw/Accurian008sm.jpg

[billbillw]

It should be noted that in this configuration (or any that bypasses the entire tone board), you are loosing a bit of overall gain. There is an opamp on the board that is being bypassed. Without that, I don't think an Ipod has enough output to really drive this amp to full power. A computer sound card might to better, but I haven't fully tested that setup yet.

[Face]

I agree. After bypassing the tone board, if I use my PDA as a source, the amp is hardly loud at all.

[ben62670]

I have been driving mine with an onboard sound card, and it has enough juice to drive it. I am curious if having it still hooked to the front panel has any adverse effects to sound level, and SQ even though the signal is not passing through it is still going to the board. My PDA was weak as well.
Ben

[madmax]

I agree. After bypassing the tone board, if I use my PDA as a source, the amp is hardly loud at all.

I didn't notice much difference. Must be something to do with impedances or something.
madmax

[billbillw]

I am curious if having it still hooked to the front panel has any adverse effects to sound level, and SQ even though the signal is not passing through it is still going to the board.
Ben

I actually tried it using a set of pins to link the two plugs together versus having them hooked directly to the tone board. It sounded exactly the same. I ended up going with the arrangement in the photo because I trusted the connectors on the tone board more than a set of rigged up pins cut from a paper-clip :D

[ben62670]

I actually tried it using a set of pins to link the two plugs together versus having them hooked directly to the tone board. It sounded exactly the same. I ended up going with the arrangement in the photo because I trusted the connectors on the tone board more than a set of rigged up pins cut from a paper-clip :D

:) Cool it wasn't a derogatory question, but something I was truly curious about. Thanks Bill
Ben

[billbillw]

:) Cool it wasn't a derogatory question, but something I was truly curious about. Thanks Bill
Ben

I didn't think it was derogatory. I was just letting you know I tried both ways and couldn't hear a difference. I was curious too. I still think I want to explore using part of the tone board and perhaps finding a way to bypass the tone controls and just keeping the balance and volume, but improving the quality of them. RadioShack sells a volume pot for about $4 that is supposed to be quite bit better than the stock one. I've got a slew of caps and opamps laying around too, so I might be able to make upgrades without spending much at all.

The reason I'd like to keep volume control is if I decide to use an external DAC running from the optical output on my motherboard versus having an external high end sound card.

[seeclear]

I just finished modding my first one, and I'm listening to "Joy to the World" through Atrium 45's using my laptop to play the mp3 as the source! So cool. Anyway, a ? from this total noob--I noticed there was some hum before I plugged in the jack to my laptop audio out. Once I plugged in the jack, the hum was totally gone. Do I need to do anything like the "toroid turning" that I saw before to deal with the hum, or is it moot if it goes away when the source is connected? I would think it is no big deal, but I thought I would ask the experts, anyway. What say you?

Edit--anyone have any use for the removed board? I can send it to a fellow polkie if they have any use for it.

[dcmeigs]

If you still want one (or another) of these, you can go to a rat shack company store- not a franchise store- and get one shipped to you house under their direct2u program. They pay the shipping. Mine just arrived. $15 plus tax shipped.

[billbillw]

If you still want one (or another) of these, you can go to a rat shack company store- not a franchise store- and get one shipped to you house under their direct2u program. They pay the shipping. Mine just arrived. $15 plus tax shipped.

Unless the store is right near you, the gas cost to go to a store might outweigh the shipping cost. I think I paid $7 for shipping two amps, purchased from the Radioshack website link that is in the first post of this thread.

[dcmeigs]

True. But you can't swing a cat around here with out hitting one.

What kind of gas hog are you driving anyway?

[billbillw]

True. But you can't swing a cat around here with out hitting one.

What kind of gas hog are you driving anyway?

I get an average of 26mpg in mixed city/hwy driving, not a Hog at all, BUT, many people are lucky to get 20mpg. Also, my car requires Premium, like many of the higher performing cars today. When I drove by the station today, Premium was over $4 per gallon.

Bottom line, if the store is more than 15 miles away, it going to be a wash for most people.

BTW,
I've completed some excellent mods to one of my amps. I'll have a write up short. Basically, I found a way to make this thing completely hum/buzz free, retain the volume/balance control, bypass all the crappy tone controls, and improve the sound greatly. Very, very little expense incurred. More later.

[maximillian]

BTW,
I've completed some excellent mods to one of my amps. I'll have a write up short. Basically, I found a way to make this thing completely hum/buzz free, retain the volume/balance control, bypass all the crappy tone controls, and improve the sound greatly. Very, very little expense incurred. More later.

That's excellent. I have been looking for a way to improve the SQ while maintaining the volume and balance. I don't care about the tone controls either. However, I think maintaining the gain of this circuit is probably a good idea so the amp doesn't sound too weak. Does your mod retain this? Can't wait for the details.

[billbillw]

That's excellent. I have been looking for a way to improve the SQ while maintaining the volume and balance. I don't care about the tone controls either. However, I think maintaining the gain of this circuit is probably a good idea so the amp doesn't sound too weak. Does your mod retain this? Can't wait for the details.

Yes, I kept one of the op-amps in the circuit but disabled the second one that is in the tone circuit.

Ok, here is what I did.

1st, I relocated the power switch to the left top rear corner (see 1st and 2nd picture). Just unscrew it from the tone board and remove the button. I glued the button back into the front panel to maintain the look.

I had to drill a small (approx 3/8") in the top side panel, then I used a wire nut as a button. Use whatever you have for that. I drilled a 2nd smaller hole in the pillar and re-used one of the mounting screws to secure it back there. Getting the AC feed away from the tone board gets rid of any sign of buzz that I previously had.

Next, I did the following mods to the board.

I removed C505 and C506 and put small jumpers to replace.
I removed both opamps and replaced the one the left side with a socket and installed a Burr-Brown OPA2134 (you can get free sample from them). I removed the 2nd one so that it wouldn't steal any power from the very limited 15V feeds.

Next, I removed C509, C510, C523, and C524. These are the last caps before, after the tone circuit. I placed jumpers across them to bridge the circuit from the output of the Op-Amp directly to the trace that feeds the output plug. (Look at the 3rd photo for details on exactly where to replace the jumpers).

I also replaced the volume pot with a RadioShack Alps pot (only costs $3.50), but this is not pictured. The RS pot wires up exactly the same, but the pins don't fit, so you need need to have jumper wires for all 6 connections. Also, the RS shaft is slightly bigger (1/4"), so you need to drill out the hole to fit. I just used a 1/4" drill bit and did it by hand (clamped the bit into the vice and hand rotated the knob down onto the bit).

This is all I have done so far, but it seems to work great. The RS volume pot tracks much better at low volumes. There is no noticeable hum or buzz. There is quite a bit of noise at full volume, but what amp doesn't have that. Its essentially quiet in the first 1/2 of the volume range, which is where it will mostly be used.

Additional mods that I plan:

I will probably remove C501/C502 completely. These are coupling caps (to block DC) that are probably not really needed. The amp board already has a set of coupling caps which would prevent any DC from getting to the amp itself.

I will probably replace the coupling caps on the amp board with BlackGates if I have the right size laying around.

I will probably also add some decent size (330uF?) electrolytics bypass caps to each of the 15V feed lines to help stabilize that supply.

I could replace some of the resistors with better quality metal film resistors (which might lower the noise floor), but at this point, it might be a case of diminishing returns.

Right now, it seems to be a very worthy amp for $20 and an handful of very inexpensive mods.

[ben62670]

Thanks for the right up. I was getting ready to dive into mine. I should have one in on Tuesday.
Ben

[dcmeigs]

Great write up. Thanks.

I don't think I understand your motivation for moving the power switch. Was it necessary?

[billbillw]

Great write up. Thanks.

I don't think I understand your motivation for moving the power switch. Was it necessary?

Absolutely! The main AC power switch being right next to the preamp board was causing an audible 60hz buzz. Moving the switch eliminated that buzz completely.

Another option would be to somehow insulate the preamp board (or the AC lines/switch), but that seemed like it would be more work.

Having that switch and those main power lines running right next to the pre- board was a very poor design choice.

Some people don't notice the buzz, but in my use as an amp for near-field speakers (sitting less than 3 feet from each speaker), the buzz was very distracting.

[maximillian]

billbillw, do you know anyone who has traced out the schematics of the preamp board? If yes, do you know if they are available online? I am thinking of doing it but don't want to waste my time if someone already has.

[billbillw]

billbillw, do you know anyone who has traced out the schematics of the preamp board? If yes, do you know if they are available online? I am thinking of doing it but don't want to waste my time if someone already has.

Not that I know of. There is a complete parts list at the DIYaudio.com site, but no schematic.

http://www.diyaudio.com/forums/showthread.php?postid=1309162#post1309162

What are you trying to figure out? I've traced the board pretty well and can pretty much tell you what everything does on the first (volume) side of the board. The only thing that I don't know is the tone control section. I didn't bother with that because I planned to bypass it anyway.

[maximillian]

I just wanted to see if there is some other things that could be improved. For example, maybe there is a way to improve the tone controls.

[billbillw]

I just wanted to see if there is some other things that could be improved. For example, maybe there is a way to improve the tone controls.

Sure there is a way to improve the tone controls: Better pots, better caps, better resistors. But that is lots of work that is not worth it IMHO. I prefer flat response anyway and usually use the tone defeat, direct mode, or whatever its called to bypass the tone controls.

[IamKai]

I agree. After bypassing the tone board, if I use my PDA as a source, the amp is hardly loud at all.

Pardon the newB nature of this question please, but is it possible to delete a resistor somewhere to bring the sensitivity up on the amp after bypassing that opamp?

It would be very nice to have it able to be used as a standard power amplifier without any of the front panel enabled. I am trying to make a simple switch setup that would allow either use at the flip of a switch.

[billbillw]

Pardon the newB nature of this question please, but is it possible to delete a resistor somewhere to bring the sensitivity up on the amp after bypassing that opamp?

It would be very nice to have it able to be used as a standard power amplifier without any of the front panel enabled. I am trying to make a simple switch setup that would allow either use at the flip of a switch.

It will work fine with the preamp board totally bypassed, but you really need a preamp type source as opposed to an ipod/PDA type device. Those devices are designed for powering headphones, not an amp. Its an impedance mismatch.

[IamKai]

I just did the mod outlined in post 171.
OMG!

I lost sensitivity to be sure, but the increase in quality is just unbelievable!!

Having several of them, I was able to match the output (the setting of the volume control) on a unit with the tone board still enabled.

There is no contest!!! I am shocked beyond words at how GOOD the thing becomes when you do this mod to it.

I wish there was a way to retain the sensitivity and keep the quality.

I am going to try the tube input mod, but I wonder if there could be a little more in the way of pictures of it to guide newB's like me through the process.

Anyone who has a good preamp available and wants to hear what that board does to the sound, should do this mod. The difference is not a subtle one.

Also, shielding the input leads to and from the plugs helps a little bit.
(Am I the only one who shielded the input wires?)

[IamKai]

It will work fine with the preamp board totally bypassed, but you really need a preamp type source as opposed to an ipod/PDA type device. Those devices are designed for powering headphones, not an amp. Its an impedance mismatch.

I found it to be quite a bit less sensitive than my Crown D150A or my Audionics CC2.
I was able to get good power from the Accurian, but it took a lot more volume out of the preamp to do it.
(My pre is an Adcom GFP-565.)

Thanks for the info on this! Had it not been so easy, I may never have tried it...now I am aware what this little thing is capable of. It really is shocking.

[billbillw]

I just did the mod outlined in post 171.
OMG!

I wish there was a way to retain the sensitivity and keep the quality.



There is. If you don't want volume control at all, just do the mod that I outlined in post #190! Or, If you don't want volume control or balance, then jumper from the 1st pin (furthest left) of the volume pot for each channel to the input legs of the opamp. That should be pin 3 and pin 5. The only thing you need to worry about keeping in the loop are the feedback caps/resistors for the opamp (R505/506, C507/508), and the small blue cap(s) and resistor(s) that are at the input (R501/502, C503/504). You can bypass C501/502.

[ben62670]

I found it to be quite a bit less sensitive than my Crown D150A or my Audionics CC2.
I was able to get good power from the Accurian, but it took a lot more volume out of the preamp to do it.
(My pre is an Adcom GFP-565.)

Thanks for the info on this! Had it not been so easy, I may never have tried it...now I am aware what this little thing is capable of. It really is shocking.

Welcome to club Polk, and glad to see you are enjoying yourself. The tube mod bumps the input voltage up to around 2.5v, and needs to be attenuated. I have not done this yet. Also I wanted to do a headphone out directly from the tube. I don't know how it would sound, but its a near free mod.
Ben

[DeadAccurian]

Hey guys.

Found this forum and thread on Google. I just lost my Accurian Sender (15-1938) to a power surge. (When plugged in, I get nothing.)

When these things were being discontinued at RS, I bought one pair of powered speakers, three stand-alone receivers, and one (duh) sender. And now my one sender is toast.

So, anyone think it can be saved? Anyone have any ideas or tips on where I could go to have someone look at it? (There's a good TV repair shop right near me; was thinking of talking to them.)

Thanks for your input, folks.

(BTW, I'm the proud, proud owner of a pair of SDA loudspeakers.)

jw

[ben62670]

Hey guys.

Found this forum and thread on Google. I just lost my Accurian Sender (15-1938) to a power surge. (When plugged in, I get nothing.)

When these things were being discontinued at RS, I bought one pair of powered speakers, three stand-alone receivers, and one (duh) sender. And now my one sender is toast.

So, anyone think it can be saved? Anyone have any ideas or tips on where I could go to have someone look at it? (There's a good TV repair shop right near me; was thinking of talking to them.)

Thanks for your input, folks.

(BTW, I'm the proud, proud owner of a pair of SDA loudspeakers.)

jw

First welcome to Club Polk.
Second have you opened up the device to see if any parts are obviously burnt? There are a lot of sensitive parts in the sending, and receiving boards in these devices. You might want to look for a sender on Ebay.
Ben

[DeadAccurian]

Hey, thanks, Ben.

Yep, opened it up looking for the obvious and all looks well. I've also looked on eBay and contacted one seller.

Do you think the parts inside are somewhat commonplace and could be replaced if neccessary? (Sorry, total noob question, but I'm not proud.)

jw

[ben62670]

The problem is there are a lot of surface mount chips on the sending board. They basically operate like TCP/IP realtek network cards(peal the label off one of the chips). The chips are fairly sensitive, and prone to failure with voltage spikes.

[DeadAccurian]

yeah, so I saw when I opened it up. Can those be replaced? Can someone with the right equipment find out which one?

(Again, sorry for the uninformed questions. Just kinda hoping I can resurrect this one and not have to try to find (and pay for) another one.

[ben62670]

yeah, so I saw when I opened it up. Can those be replaced? Can someone with the right equipment find out which one?

(Again, sorry for the uninformed questions. Just kinda hoping I can resurrect this one and not have to try to find (and pay for) another one.

I think it would be hit or miss. Most likely miss, it will still cost ya, and I don't know how good the repair would hold up. MHO

[IamKai]

a tech friend of mine said that they usually had issues with the pwr supply and not the 'radio' portion of the device.

if you had a couple of test leads and a meter, you could do a preliminary check of the thing. It could be something really silly and simple.

the manager at one of the storess told me they do have the transmitters for the people who had the extended warranty on them. How true that was, I dunno.

[IamKai]

Welcome to club Polk, and glad to see you are enjoying yourself. The tube mod bumps the input voltage up to around 2.5v, and needs to be attenuated. I have not done this yet. Also I wanted to do a headphone out directly from the tube. I don't know how it would sound, but its a near free mod.
Ben
If you plan on doing this modification, I sure would like to see pictures of it step by step.
It has intrigued me since I first saw it.

[ben62670]

If you plan on doing this modification, I sure would like to see pictures of it step by step.
It has intrigued me since I first saw it.

Its burried in this thread somewhere. Fredv has done it;)

[maximillian]

I removed C503 and C504 and put small jumpers to replace.
I removed both opamps and replaced the one the left side with a socket and installed a Burr-Brown OPA2134 (you can get free sample from them). I removed the 2nd one so that it wouldn't steal any power from the very limited 15V feeds.


Thank you again for this write up. I have made the changes you mention but can't try them out until I get home tonight. One thing I noticed is that I think you mean C505 and C506 instead of C503 and C504.

The only additional thing that I did is put a Vishay EMI filter cap on the on/off PCB (which I am placing in the same location as you but on standoffs).

I got the idea here:
http://www.10audio.com/diy_power_conditioner.htm

I will write back on how it sounds.

[billbillw]

Thank you again for this write up. I have made the changes you mention but can't try them out until I get home tonight. One thing I noticed is that I think you mean C505 and C506 instead of C503 and C504.

The only additional thing that I did is put a Vishay EMI filter cap on the on/off PCB (which I am placing in the same location as you but on standoffs).

I got the idea here:
http://www.10audio.com/diy_power_conditioner.htm

I will write back on how it sounds.

Thanks for catching my error. I went back and edited that post and made a couple slight changes.

[maximillian]

Helllo Bill,

I made the changes you outlined except I didn't change the volume pot yet. I still get a buzz sound that can change when I touch the pots bare metal shaft. Even if I put the plastic knob on I can sometime get a noise change when I touch the edge front plastic bezel. I can even touch the bare shaft the tone controls and get the same effect. Will changing the potentiometer eliminate this? Do you think the Vishay cap is adding noise? It seems to me that the tone control board's ground is very poor.

I appreciate the help.

[billbillw]

Helllo Bill,

I made the changes you outlined except I didn't change the volume pot yet. I still get a buzz sound that can change when I touch the pots bare metal shaft. Even if I put the plastic knob on I can sometime get a noise change when I touch the edge front plastic bezel. I can even touch the bare shaft the tone controls and get the same effect. Will changing the potentiometer eliminate this? Do you think the Vishay cap is adding noise? It seems to me that the tone control board's ground is very poor.

I appreciate the help.

That's because they cut the grounds on all of the control pots. If you look at the back, you can see this. It was like an after thought. Apparently the front panel is somewhat conductive too. Anyway, I I noticed the same thing, but it went away when I put everything back together. Make sure your power wires are all kept in that back corner.

[maximillian]

That's because they cut the grounds on all of the control pots. If you look at the back, you can see this. It was like an after thought. Apparently the front panel is somewhat conductive too. Anyway, I I noticed the same thing, but it went away when I put everything back together. Make sure your power wires are all kept in that back corner.

There is something really weird with the balance pot. I don't have time right now to investigate but two things I have noticed...
1) There is 68 Ohms between one of the channels and the pot's ground lug.
2) I have excessive noise in one of the channels, same one as in #1. If I unscrew the shaft's nut then the noise goes away. It seems like the front panel is conductive noise from one pot to the other.

I will try to look into it tomorrow night.

BTW, I removed the filter cap since it seemed worse with it in.

[schwarcw]

Kudos to Ben, Bill , Max, Fred, Madmax and man others who have contributed the 217 posts to this thread.

We could use someone ambitious to summaerize these into a DIY book with pictures, where to buy parts, various options, etc. I think you could eith offer this book for a nominal price to Polk members, or sell it ti the DIY /forum guys.

I think there's a couple of bucks to be made here.

Me, I have two of these little amps but I'm just waiting for someone to hit a home run with a DIY design. I think you guys are getting close.:)

[ben62670]

Working on it. I just received some more to play with. But really the total front panel bypass is the simplest mod that yields the best results. Fred's is probably the best SQ mod so far. Thanks guys guys. For the most part I have just been regurgitating info from here, and DIYaudio.
Ben

[seeclear]

anyone have any use for the removed board? I can send it to a fellow polkie if they have any use for it.

Anyone have any use for the removed board, or should I just chuck it?:confused::confused::confused::confused::eek:

[maximillian]

I made some additional mods and the unit is pretty much quiet now. I have started with Bill's mods. In addition I have done the following simple mods:

1) Insulate the potentiometers from the front panel. I cut the alignment stub off the potentiometers then applied insulating tape (I used Kapton) to the shaft hole in the panels for the volume and balance pots.

2) Shorted the volume potentiometer's ground terminal to the signal ground. It's cut on the PCB. I tried doing the same to the balance pot but this killed one of the channels (the same one with 68 Ohms).

With these two mods the amp is very quiet. Over three feet away I cannot hear any buzz/hum.

The last thing that pretty much eliminated the buzz/hum is to earth ground the heat sink/rear metal panel. I noticed that if I applied a finger to either the signal ground or the heat sink the little amount of noise vanished. The best solution I have for filtering this out at this point is by grounding the heatsink. I don't know where this noise is coming yet. It could be the crappy +/-15 supply but I don't have access to a scope to tell.

Grounding the heatsink is not the easiest thing to do. I know that a power inlet adapter can be bought that has the earth ground on the connector. I am going to find one and put a simple screw/lockwasher on the rear metal panel and jumper it to the inlet adapter panel. An alternate is to cut into the power cable and splice into the earth conductor.

Will keep you posted.

[maximillian]

I forgot to mention a couple things...
1) I did not change the pot as per Bill's mods.

2) The metal panel is connected to the audio signal's ground. So tying this to earth ground means the audio signal's ground (say from an Ipod) is tied to earth ground. So your source's signal ground would be tied to earth ground. Is this a "bad" thing to do? I think it may have the potential to create a ground loop. Thoughts? I will still look into better filtering instead of earth ground connection.

[schwarcw]

There seems like some really fundamental things that can be done to make this little amp sound much better. The bypass on the front end tone controls with the potentiometer seems to be the big back for the buck. Is the Rat Shack the best or does Parts Express have a smoother, quieter one. Isolating the potentiometer also seems to reduce some noise. The transformer also seems to provide some hum. Rotating the unit it goes away seems to be the solution. I also see some cap change out are also a potential for some improvement. the front end tube preamp also is intriguing. What about some changes to the power supply? By-pass caps? Better components. All these suggestions have been made under the guise of making some inexpensive modifications to a bargain unit and making it sound better.

My point was, may some of you guys can organize these experiences from the always brilliant members of Club Polk with some of the DIY forum enthusiasts. A short ten page manual with pictures and step bu step directions may become a popular publication.

Just my meager $0.02.

good luck!

[maximillian]

Finished the ground mod. I changed the inlet connector to one that was the same size for the panel hole but had the ground connection. I also tied two filter caps between both the line and neutral and ground (similar to the one that is there now). I am not sure if they are really needed. Then I drilled a hole in the rear panel and tied the ground wire here with a star washer and ring terminal.

The unit is really quiet. I am calling it quits for now. The noise that occurs when you touch the front panel or the exposed shaft of any of the controls is almost eliminated too.

Finally, I switched the left-right connectors for the input and output connectors to the pre-amp board to fix the reversed channel problem.

There is still some hum/buzz that is loudest in the middle position of the volume knob. It is almost unnoticeable under 2 feet.

The hum/buzz completely goes away when I put my finger on the input signal connector solder terminals on the preamp board. I think it has to do with signal ground still being noisy. I think cleaning up the +/-15V may