Balance pot not working the way it should - diyAudio
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Old 6th November 2010, 10:03 PM   #1
Makk is offline Makk  Finland
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Default Balance pot not working the way it should

Hey,
I have problem with my LM3886 gainclone amp balance pot. I have 10k log volume pot and 100k linear pot with centerclick. Both are stereopots. I'm using assembly shown in the picture.

The problem is that there is no hearable difference between L and R volume before the very last section of balance pots movement. There it is too fast and very hard to control, but working. I tried 220ohms resistor parallel with pot (between balance in and ground) and calculated resistance should be something below 10ohms then when pot in CC. Even then the action of the pot remains the same.

I'm using stereo pots both channels, so there is no speak between L and R. At CC there is 50k resistance per channel between in and ground.

What am I doing wrong?
I want to have configuration like this, which has only grounding at balance pot and no "out". That's because my wiring.
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Old 6th November 2010, 10:08 PM   #2
audi0 is offline audi0  Australia
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Rod Elliott's site has a great article on potentiometers, gain and balance pots and their connection Potentiometers (Beginners' Guide to Pots)

Last edited by audi0; 6th November 2010 at 10:09 PM. Reason: spelling
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Old 6th November 2010, 10:29 PM   #3
Makk is offline Makk  Finland
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Yes it has. I've read that couple times but it doesn't answer my question. The only thing I can find there to answer my question is that this setting that I'm using is almost as good as the little more complex setting he brings up.

"The balance control as shown above (with the values shown) will give a response very similar to the more complex version described in the next section."

Difference between his scheme and mine is that I have 100k balance pot, he has 10k. He also has one resistor before balance pot. I have no acknowledgement why it's there, but I think that has no effect in my situation.
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Old 6th November 2010, 10:38 PM   #4
audi0 is offline audi0  Australia
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Hi Makk,
Have you tried connecting the pots as Rod's drawing shows? Your drawing above appears to be wrong.
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Old 7th November 2010, 09:17 AM   #5
Makk is offline Makk  Finland
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Hmm. I'm wondering is there any difference if balance pot is after volume pot. I have to check in the evening how I wired volume pot, but my memory says I did it like in the picture above. Not like in Rod's figure. If it's so I have to rewire that because Rods wiring is better cause it always has resistance between earth and signal. Mine shorts them in when volkume is zero.
Anyway, I don't see why volume pot wiring would affect my balance pot work this way. What is the problem? Is it 100k pot or what?
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Old 7th November 2010, 06:57 PM   #6
Makk is offline Makk  Finland
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I checked the wiring of the volume pot and it was done like in Rod Elliots site. In my wiring there is balance pot (100k LIN) after volumepot (10K LOG). My balance pot does what it is meant to do, so I can leave it that way. But fixing it would be the best. It's little cheapish now..
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