B1 Buffer Preamp

[zingo]

I am going to start point-to-pointing the Pass Labs B1 Buffer Preamp (http://www.enjoythemusic.com/Magazine/equipment/0708/first_watt_b1_preamplifier.htm) in a week or two when I get some time. I have attached the schematics with transposed part specs for anyone else who wants the information.

[zingo]

http://img108.imageshack.us/my.php?image=b1bufferpreampti0.pdf

[strider]

Did you give up on waiting on the PCB? I've been checking the site every once in a while and haven't seen them become available again.

I'll look forward to your updates.

[zingo]

I did get tired of waiting for the board... And since it has so few parts anyway, I'll just get a breadboard and do it myself.

[strider]

I ended up buying one from Tim Rawson instead of trying to build one without the board. Even though there's a low parts count and it seemed pretty straight forward, I got intimidated/confused reading the threads on diyaudio.com.

[zingo]

Ya, those threads were a little intimidating, but I figure that's the best way to learn. :D

[Face]

http://www.cleanandquiet.com/upload/store/Pass%20B1.jpg

[GV#27]

I posted the B1 schem awhile back.http://www.polkaudio.com/forums/showthread.php?t=69722&highlight=PASS+PREAMP.Looks like a great little pre,if I didn't already have a Pass Jfet clone then I would probably build one of these or the B3.If I where to build it I think I would use the bipolar 9 volt power supply so as to eliminate the need for costly output caps.

[Face]

Btw, I would avoid using Jantzens that are in the picture above.

[zingo]

What was wrong with the Jantzen caps? I used them in my Monitor 5Jrs with good success.

[zingo]

If I where to build it I think I would use the bipolar 9 volt power supply so as to eliminate the need for costly output caps.

I was looking at running it off a pair of 9v batteries to totally avoid A/C. Am I missing something with the bipolar power supply? The specs sheet says it required between 18-24v.

[Face]

What was wrong with the Jantzen caps? I used them in my Monitor 5Jrs with good success.
IMO, I thought they sounded terrible in the B1. I replaced them with Sonic Caps and there was a large improvement. They may not be as bad in a speaker crossover.

[GV#27]

I was looking at running it off a pair of 9v batteries to totally avoid A/C. Am I missing something with the bipolar power supply? The specs sheet says it required between 18-24v.You can use a single 18 volt supply or a +-9 volt.I haven't checked the thread at DiyAudio in awhile but I think some builders intended to use batteries.

[zingo]

Where did you get the chassis Face? Your completed product looks fantastic!

[GV#27]

Where did you get the chassis Face? Your completed product looks fantastic!
If you are looking for a nice chassis for your B1 one of these Hammonds would do nicely.http://www.hammondmfg.com/1455ptbla.htm
They come in several sizes and with either plastic or metal fronts. I have used them for several projects.I used a small one for this passive pre.

[Face]

I bought mine used and I believe the case is unavailable.

[GV#27]

I bought mine used and I believe the case is unavailable.
Too bad because they look great.


What didn't you like about the Z caps?

[GV#27]

What didn't you like about the Z caps?Oooops,make that Jantzen caps.

[Gaara]

Where did you get the chassis Face? Your completed product looks fantastic!

For my last couple projects Tim went with Diyenclosure (http://diyenclosures.com/). Not sure if it is the same company but it looks similar to my BPA200 and 200asc, just smaller.

[Face]

Oooops,make that Jantzen caps.
I found them rolled off up top and not very coherent.

[ben62670]

I found them rolled off up top and not very coherent.

Thats what I got doing my cap shoot out on speakers. Solen's were too hot brittle, Jantzen's were better, but kinda lifeless, and Dayton's came out on top.

[zingo]

I'm kind of surprised that I liked them then in my 5Jrs, because I really like the Sonicaps in my 4.1TLs. Or maybe they just work well with those speakers. I will be building this with Daytons however since I have had good results with them in electronics before.

[strider]

Are the Jfet's hard to source for this thing, or am I remembering incorrectly?

[zingo]

I believe that the 2SK370 can be hard to find, but here is a link to the also approved LSK170:
http://www.ka-electronics.com/FETS/FET.htm

FYI: The 2SK170 is also approved to be used

[zingo]

Parts List:

2SK370 Transistor 4x
1N914 Diode
Generic LED
15000 uF 2x
10 uF 2x
1 uF 3x
1 ohm
1k ohm 4x
10k ohm 2x
15k ohm
25k ohm 2x
221k ohm 2x
1M ohm 6x
2 way switch
RCA jack 6x

[Face]

I remember reading that if you contact Pass Labs, they may be able to sell you a board. They're leaving the "out of stock" message up on their page due to them not being able to meet demand.

I may actually grab a second one.

[zingo]

Updated Parts List:

2SK370 N channel JFET Transistor 4x (GR or BL grades)
1N914 Diode
Generic LED
15000 uF 2x Electrolytic 25v
10 uF 2x Film
1 uF 3x Film
1 ohm 3w
1k ohm 4x .25w
10k ohm 2x .25w
15k ohm .25w
25k ohm 2x .25w
221k ohm 2x .25w
1M ohm 6x .25w
2 way switch
RCA jack 6x
Linear Taper Pots 25k 2x

[zingo]

I remember reading that if you contact Pass Labs, they may be able to sell you a board. They're leaving the "out of stock" message up on their page due to them not being able to meet demand.

I may actually grab a second one.

The first time I contacted them, they said they were out. I contact them back a month later a few times but haven't received any updated responses. I figured since there were so few parts and it's not high voltage, point-to-point would be a good route.

[Face]

http://www.cleanandquiet.com/upload/store/Pass%20B1.jpg
http://face.cleanandquiet.com/store/B1%20MR.jpg

[strider]

New wiring, Mike?


Daytons in mine. Finally checked tonight.

[Face]

New wiring, Mike?
Kinda. ;)

Daytons in mine. Finally checked tonight.
Good! Be glad.

[zingo]

Are those really the same value caps? WOW

Whats' the wiring for your power supply? I was originally wanting to use batteries, but I haven't been able to find anything to fit the bill.

[Face]

Are those really the same value caps? WOWYes, but unfortunately the cover no longer fits.


Whats' the wiring for your power supply? I was originally wanting to use batteries, but I haven't been able to find anything to fit the bill.
Beats me, but I know it's not the same as the schematic.

[zingo]

The schematics don't have a power supply, but it should be pretty easy to replicate.

[Face]

Sorry, not the PS, but by the 15,000uf caps, a trace on the board was removed and something else was changed. I should have taken a picture when the board was free of film caps.

[strider]

Mine looks pretty similar to Mike's, Jake. I've got the top off and my caps don't have elephantitis, I'd be happy to take a couple pictures of it if it would be of help.

My transformer's much smaller and only has 2 leads going in and 2 going out. Other then that it looks to be the same.

[zingo]

Thanks but don't worry about it. It's easy enough to throw an 18v transformer on there with a rectifier, or just a regulated wall wart. :D

[zingo]

Would I be able to use a 20000uF cap in place of the 15000uf filter cap?

http://www.diyaudio.com/forums/showthread.php?s=&threadid=135652

[ShinAce]

The 26000uF is smaller and cheaper and still meets voltage spec.

One of the caps is a filter, so bigger is fine. The second 15000 uF is part of a voltage divider and can still be replaced with a bigger one.

[zingo]

But who doesn't like Big Blue? :D

(But I'll probably just use the spec'ed caps to save space.)

[zingo]

For the selector switch, will any two way switch work?

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=060-424

[GV#27]

For the selector switch, will any two way switch work?

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=060-424

If you only want to switch between 2 sources then a DPDT switch is needed.That switch at PE is only a single pole(1 channel).Check the C&K toggles at Digi-key.7202 I believe is the #

[zingo]

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=060-310 :D

[zingo]

I also need a good source for a stereo pot/attenuator...

[GV#27]

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=060-310 :D
That would work ,but my preference would be for a better one like this.http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CKN1032-ND I suspect that the internal contacts will be superior.


As for attenuator one of the stepped variety would be ideal,I have seen some decent looking ones on Ebay(Asian sourced) for $30ish.If you want dual 25K's as in NP's schem then the Bourns 91 series or Clarostat conductive plastics from Digi key would be good choices. http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RV4NAYSD254C-ND
Partsconnexion sells the Blue Alps ganged pots but only in 10k and 100k.The 10k would likely work fine.

[GV#27]

25k dual stepped atten. http://cgi.ebay.ca/25K-24-Step-Ladder-Type-Stereo-Volume-Attenuator_W0QQitemZ300294869752QQihZ020QQcategory Z12050QQcmdZViewItemQQ_trksidZp1742.m153.l1262

[nikolas812]

How far along in your build are you?



I got in on a group buy for a B1 board over the DIY forum. So I'll be building one of these at some point and time...:)




Nick

[fredv]

How far along in your build are you?



I got in on a group buy for a B1 board over the DIY forum. So I'll be building one of these at some point and time...:)




Nick
Why not calling Collins to get a genuine Pass board and order the jfets at the same time? Many members got one shortly after contacting Collins. I will do p-2-p if I am building ones. I have all the parts needed but no time, sigh ....

Have fun!!

[zingo]

I am starting to collect the parts for the B1 and will probably start the build within the month. I will not be using a printed board as I thought this would be good P2P practice, and the boards themselves costs as much as the collective parts.

[nikolas812]

Why not calling Collins to get a genuine Pass board and order the jfets at the same time? Many members got one shortly after contacting Collins. I will do p-2-p if I am building ones. I have all the parts needed but no time, sigh ....

Have fun!!



I'm pretty sure these are coming straight from Nelson Pass...

There should be a thread in the Group buy forum at the DIYF with specifics...




Nick

[fredv]

I'm pretty sure these are coming straight from Nelson Pass...

There should be a thread in the Group buy forum at the DIYF with specifics...




Nick
I know you are talking about the Rhys GB. They will be made with the approval of Nelson using the First Watt Gerber file, not coming straight from Nelson. There is nothing wrong with this, but not much of a saving for that price.

[zingo]

I just saw on the DIYaudio site, a builder who installed the B1 circuit into his Goldpoint. If I had a choice, that would be my new build direction, but one of those units is anything but cheap.

http://lh3.ggpht.com/_pEmsvoRBmXg/SZ8U7hul9VI/AAAAAAAAACg/QwWXGz7THnU/s512/P9290159.jpg

[Face]

I have one of those and thought about doing the same thing, but I thought space would have been too tight. He must have installed the filter caps externally...and he used Solen caps(yuk).

[zingo]

How much power supply filtering capacitance do I need on this preamp? Is 15000uF required for the pair of caps? (It's just that they are pricey and a little hard to find)

[GV#27]

....

[zingo]

Would a value like around 10000uf work okay, or should I stick with 15000uf?

[SoundEngine355]

http://www.cleanandquiet.com/upload/store/Pass%20B1.jpg

What potentiumeter did you use?

[Face]

It's an alps unit. I have a spare goldpoint there will eventually be swapped in there.

[SoundEngine355]

It's an alps unit. I have a spare goldpoint there will eventually be swapped in there.

Is that the Goldpoint Precision Mini-V Level Control? I heard DACT is very good. Is the Goldpoint on the highend side?

[Face]

Same brand, older model though: http://www.cleanandquiet.com/upload/store/Attenuator%202.jpg
It's a step above the DACT I have installed in the B1.

[vc69]

What would one of these little pre's cost? I'm no DIYer, but this is exactly what I am interested in trying in my system.