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Old 17th November 2007, 04:23 PM   #1
DeanP is offline DeanP  Canada
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Question GainClone ground loop help

Hi,
I know I have a ground loop problem, but would like advice on how to delete it.
The two lowpass amp boards are the "parallel" type amps and the high pass amp board is a "stereo" type amp.
All three are from Peter Daniel (LM4780s).
All three are powered from a single source and the PG - & + are daisy chained on the amp boards as well as the V - & +.
The "chassis grounds" are also daisy chained to a common ground via a 10r resisitor.
In the attached JPEG is the wiring diagram that I used.
I believe I should connect all grounds after the x-overs from the pot to a single wire and run this to the amp boards as shown in green.
Do you think this is a good idea?
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File Type: jpg signal ground paths for gain clone.jpg (22.4 KB, 555 views)
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Old 17th November 2007, 04:43 PM   #2
okapi is offline okapi  United States
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is the pot attached to the grounded chassis?
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Old 17th November 2007, 04:45 PM   #3
okapi is offline okapi  United States
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i am also having trouble distinguishing what is power vs signal in your diagram.
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Old 17th November 2007, 04:51 PM   #4
okapi is offline okapi  United States
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oops. i guess it is all signal. a seperate diagram of the power hookup might be helpful. a photograph would be useful as well.
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Old 17th November 2007, 04:54 PM   #5
DeanP is offline DeanP  Canada
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Quote:
is the pot attached to the grounded chassis?
Yes, but when I measured the resistance I get 10r and I also physically removed it(unattached it & held it in my hand) and I still got the noise.

Quote:
i am also having trouble distinguishing what is power vs signal in your diagram.
I'm only showing the signal + & - wires, no actual power supply wires...
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Old 17th November 2007, 04:57 PM   #6
DeanP is offline DeanP  Canada
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Quote:
a seperate diagram of the power hookup might be helpful.
Quote:
All three are powered from a single source and the PG - & + are daisy chained on the amp boards as well as the V - & +.
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Old 17th November 2007, 08:03 PM   #7
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If the potentiometer is for low pass only you do not need to run high pass grounds through it.
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Old 17th November 2007, 08:08 PM   #8
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Run all signal grounds separately to each amp board and don't tie them together.

Connect all power grounds (preferably at OG points) with a single high gauge wire. From PS run PG+ and PG- to the central point on that wire. That becomes your star ground. From here, have a single connection to chassis through 10R resistor.

It is similar to what I described here: http://www.diyaudio.com/forums/showt...773#post787773
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Old 17th November 2007, 10:46 PM   #9
DeanP is offline DeanP  Canada
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Quote:
If the potentiometer is for low pass only you do not need to run high pass grounds through it.
The x-over has these out connections: low, high & ground.
So would this mean I would continue the ground at the pot to the appropriate low pass amp board? As of now, I only have a ground wire from the x-over to the pot and it ends there.

Quote:
Run all signal grounds separately to each amp board and don't tie them together.
So if I am interpeting this correctly:
(Applicable for each channel.)
-x-over ground >pot >low pass amp
-x-over ground >high pass amp(stereo board)
and do the same for the other channel?

Quote:
Connect all power grounds (preferably at OG points) with a single high gauge wire.
Yes, I thought of this for the ps but I don't have any problems for my other two stereo boards that share their own ps system. [I built a 6 channel + two(parallel, low pass amp)So I actually have five boards total]
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Old 18th November 2007, 12:50 AM   #10
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Default Re: GainClone ground loop help

Maybe you should try this first:

Quote:
I believe I should connect all grounds after the x-overs from the pot to a single wire and run this to the amp boards as shown in green.
Then the other suggestions.
Also, disconnect the chassis grounds, you don't really need them and maybe this is causing the loop?
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