How do I create a common ground on adcoms

[fbm211]

Hi again you everyone.I just pulled my amps out of storage and want to know how I should strap my neg speaker terminal to the chassis.Should I just run a wire(not bare)from the terminal and just loosen one of the screws on the chassis, wrap the wire around it, and then tighten back down.The screws appear to be painted black as well as the chassis housing.And does ANYONE know if a panamax with a ground lug would have the same effect. This is for the SDA-2b set Ill be getting thursday.

[Lasareath]

Joe (hearingimpared) has done this. You should really ask him. But I'm pretty sure he straped the Negs together and also the two casings.

He had a very heavy 10 gauge cable screwed down into the top of each casing and a cable that went from the neg terminals.

But please ask more people before doing this, since I never did.

[heiney9]

Ok, I hope this doesn't come off as being a jerk but have you searched for your information. It took me 45 seconds to come up with this post (imagine if you spent 15-20 minutes). There are many more that deal with this question. I'm assuming you are talking about the GFA-565's as you didn't give a model # in your original post.

http://www.polkaudio.com/forums/showpost.php?p=142668&postcount=18

Good luck and enjoy your new SDA's.

H9

[mrbigbluelight]

The "Search" function on CP is, I think, a "Hit or Miss" proposition on CP.

Heck, I can do a "Search" for the word "Music" on "Any Open Forums" and come up with nothing but air.

:confused:

[hearingimpared]

I believe I told you this before. Go to advanced search and key in my name.
Select Find Post by User. then search through the two ch, electronics , vinatage speakes, an the elelctronic categoys there should be tons of detailed infor in tohose threads. I know wrote them. You can also search on darqueknight that will get you all the infor you need,. You can also search on f1nut and find a plethora of info.

[heiney9]

The "Search" function on CP is, I think, a "Hit or Miss" proposition on CP.

Heck, I can do a "Search" for the word "Music" on "Any Open Forums" and come up with nothing but air.

:confused:

This is true. I typed in "Common ground Adcom" and I got a lot hits and one would have to spend some time wading through and scanning many posts. But, that's what it takes to get the info sometimes.

Again I wasn't trying to be a jerk to the OP, but sometimes when I answer questions the first thing I do is use the search function and it amazes me how quickly I can come up with something. If I can, others can as well.

Anyways not trying to beat this into the ground as it's a very minor issue and I just threw out a basic suggestion.

fbm211, let us know if you need other help once you get things up and running. Definitely take some pics and let us know what you think of the SDA's :)

H9

[I-SIG]

I've searched for "SDA" and gotten nothing, so....

Wes

[hearingimpared]

Dude I searched the db and i know it is there. Have some patience.

[SCompRacer]

Try searching

common ground

and select Search Titles Only.

[Face]

I've searched for "SDA" and gotten nothing, so....

Wes
You'll have the same response with any 3 letter search. You have to add a star to the end, ex: SDA*.

[hearingimpared]

Check this thred. (http://http://www.polkaudio.com/forums/showthread.php?t=50140)


and this (http://www.polkaudio.com/forums/showthread.php?t=43477)

here are the tweets (http://www.polkaudio.com/forums/showthread.php?t=48511)

This should provide you with everything you need. (http://www.polkaudio.com/forums/showthread.php?t=50391)


THEYA FOLKS ANODER SADISFIDE CUSTOMA!!!!

[fbm211]

I think I got it now. But lets make sure I got it right. First I connect the neg speaker terminals together on each amp and connect them to the chassis using one of the case screws.I also run a cable between the two amps to connect them together.(chassis) Hope thats it. Let me know. And I would like to thank all of you for answering all the questions I had over the last week.Im going to find a ground loop isolator now for my cable(tv).

[hearingimpared]

Let's simplify it further. Connect the two speaker ground terminals together. Next connect a screw from each amp to heavy guage piece of wire and connect it together.

TAke a VOM and check your work. You ohm reading from speaker neg to speaker neg shoud be zero. The reading from your two separate chasis should also read zero .

[fbm211]

I dont have a vom but Ill get one this friday. Lets verify something.I was thinking that I could get 2/8ft heavy guage cables and terminate 1 with bananas and the other with spades.And run the one w/bananas to the neg speaker terminals of each amp.And the one with spades to each chasis. No-one mentioned that these amps have 4 binding posts so I still have a free negitive terminal free for the set of highest grade canare 4S11 speakercables I ordered (terminated with vampire bananas). And a cool 30 day satifaction garantee or money back.

[Boywonder]

The Continuity checks mentioned by hearingimpared above are strongly encouraged before you power everything up. Doesn't take very long to let the smoke out of your electronics if things aren't connected correctly.

The idea is to convince yourself that both speaker neg terminals are at ground potential, same as chassis. Some amp designs float the speaker negative connections above ground potential, and this can be problematic with SDA's.

I also suggest that you plug both amps into the same wall recepticle (they are both grounded to your house wiring at the same point, so no ground potential difference between them). You may not need to tie the two chassis together if you get continuity between a chassis screw (any chassis metal) on each amp when they are plugged in, as the ground conductors on the power cords are already tying the chassis together.

As a sanity check, you can also check voltage between the speaker negative terminal and chassis with the amp powered up and no speakers connected, it should be millivolts, ie very close to zero. A multimeter set on VOLTS is an open circuit so you will not short anything with the meter when measuring voltages.

[heiney9]

Refer to page 4 & 5 of the owners manual. If you don't have one here's the link.

http://www.adcom.com/data/manuals/gfa565manual.pdf

Each mono has 4 posts these are for bi-amping a single speaker or running (2) sets of speakers in parallel.

I'm not an EE but I'm assuming which ever set of binding posts you decide to use that is the neg terminal you tie together. I am also assuming if you are going to bi-amp your SDA's then you would tie BOTH sets of (blk) negative terminals together.

So to re-cap.

Use heavy gauge wire to tie the (blk) negative terminal(s) of each channel (R & L) to each other.

Then find a screw on the chassis of each amp and use regular piece of insulated wire to tie the (2) chassis together.

It's my understanding the chassis does not need to be tied to the speaker terminals. But, perhaps a call to Ken at Polk might be in order. I did post a link earlier that pretty much explained this.

The use of MM is mandatory before final hook-up to make sure you have achieved common ground

H9

[fbm211]

Im not going to biamp or biwire.And I called frank at signal cable this morning and asked him to make me a special cable for this common ground project.He is going to make me a cable that has one wire terminated with bananas at each end(for neg speaker terminals) and the other wire with small spades at each end.(for chassis connection)He is using the entry level speaker cable.6ft.A bit expensive for this but...I got caried away.I assumed the 2 neg speaker terminals on each amp are tied together(internally)Let me know if Im wrong so I can call frank and make all the terminators spades. i will also be hooking up the amps, preamp, cdplayer, etc to a tripplite voltage regulator/line conditioner.

[heiney9]

Im not going to biamp or biwire.And I called frank at signal cable this morning and asked him to make me a special cable for this common ground project.He is going to make me a cable that has one wire terminated with bananas at each end(for neg speaker terminals) and the other wire with small spades at each end.(for chassis connection)He is using the entry level speaker cable.6ft.A bit expensive for this but...I got caried away.I assumed the 2 neg speaker terminals on each amp are tied together(internally)Let me know if Im wrong so I can call frank and make all the terminators spades.

I think nanners are a good idea for the neg speaker terminals as the cooling fins on the rear make it difficult for spades.

As far as the chassis ground cable goes, it doesn't need to be super thick. Just make sure the spade isn't too large to fit under a chassis screw or you may have to rig it up a bit with a washer or something like that.

H9

[fbm211]

Ill have a MM friday and I just talked to ken at polk and he assured me this should work.And frank suggested small spades for the chassis ground before I even asked for small ones.Rest assured I will be buying more cables from signal cable later on.He has a nice gold plated mini plug to rca cable Im going to get to plug my pc into the preamp.COOL

[heiney9]

Ill have a MM friday and I just talked to ken at polk and he assured me this should work.And frank suggested small spades for the chassis ground before I even asked for small ones.Rest assured I will be buying more cables from signal cable later on.He has a nice gold plated mini plug to rca cable Im going to get to plug my pc into the preamp.COOL

Great! :cool: Signal Cable is a great company and Frank is as honest as they come.