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Question about channel balancing.
Question about channel balancing.
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Old 7th April 2019, 08:34 AM   #1
rich1051414 is online now rich1051414
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Default Question about channel balancing.

I wasn't really sure where to put this as it wasn't really appropriate for any of the given topics, but I suppose it will work here.

I am wanting to make a simple passive box between my dac and headphone amp where I can adjust the channel balance. I plan to do it with a single dual gang 100k pot. My idea is to run the ground on the left on the top gang, and the ground on the right on the bottom, so that when you turn it one way, one channel gets louder while the other gets quieter, and the other way, vice versa.

Obviously this will mean the volume will be cut in half right off the bat, but will that be a huge issue if I do it before the actual amp? Is there a better way to do a single knob balance without the issue of the volume being cut in half?

Last edited by rich1051414; 7th April 2019 at 08:36 AM.
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Old 7th April 2019, 08:42 AM   #2
Mooly is offline Mooly  United Kingdom
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Question about channel balancing.
Its best if draw what you have in mind tbh.

If you are relying on the shunting action of the pot (its decreasing resistance) being placed across a DAC output then that won't work because the output impedance of the DAC will be so low that nothing will happen until you almost short it out.

If you meant wiring a linear pot up and taking the signal from the wiper at the midpoint setting then yes that will work, however 100k is very high and could cause HF roll off issues. That's really wiring the pot so that one side works as a normal volume control and the other works in reverse.

Best to draw it
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Old 7th April 2019, 01:05 PM   #3
rich1051414 is online now rich1051414
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"That's really wiring the pot so that one side works as a normal volume control and the other works in reverse. "



That is exactly what I mean. Screenshot by Lightshot

I'll try it out and see how it works for me. If the volume becomes too low for a usable line level, I guess I will try something else. Maybe an extra resistor to each ground to limit the range and give me more headroom. I don't think I will need to to pan fully left or right anyways.

Last edited by rich1051414; 7th April 2019 at 01:15 PM.
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Old 7th April 2019, 01:27 PM   #4
Mooly is offline Mooly  United Kingdom
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Question about channel balancing.
So assuming the DAC is capable of driving 600 ohm loads (such as NE5532 opamp etc) then I'd use something like a 2k or 5k pot.
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Old 15th April 2019, 02:35 PM   #5
rich1051414 is online now rich1051414
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Thanks guys, worked great! Volume turned out to be a non-issue.

Next, for a totally different project, I am wanting to make a passive crossfeed box, where a small bit of the left channel will feed to the right channel and a small bit of right channel feeds to the left.

This is what I am planning to do, so you can understand.
Basically, when the knob is all the way left, everything is normal(with minimal crossfeed), when in the middle, the output is basically mono, and all the way to the right, the right and left channels are inverted. Will this work out? I know these three positions will be fine, but I am unsure about everything in the middle, if it will effect frequency response, and what will happen in regards to destructive interactions of the sound.
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Old 15th April 2019, 05:48 PM   #6
Mooly is offline Mooly  United Kingdom
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Question about channel balancing.
Pleased it worked out OK.

I think you might start to get odd cancellation effects with the second idea as the pot is around the centre. Exactly what will happen depends on the phase relationships of the signals.
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Old 16th April 2019, 04:18 AM   #7
PRR is online now PRR  United States
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Question about channel balancing.
Looks like the Panorama knob from a hi-buck amp of the 1960s, maybe Mac?

It won't kill your dog. Just try it.
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Old 16th April 2019, 12:33 PM   #8
rich1051414 is online now rich1051414
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Quote:
Originally Posted by PRR View Post
Looks like the Panorama knob from a hi-buck amp of the 1960s, maybe Mac?

It won't kill your dog. Just try it.
I did, and the only issue I have is, the volume decreases towards 50%, and increases towards 0% and 100%. After matching the volume, I can't hear much frequency response issues, although the signature alters slightly to the warm side. It is difficult to know if it is in my head though, since at lower volumes, the low end would be more audible anyway.

Overall, it's a success, but it would be nice if the volume discrepancy wasn't a thing, but I can't think of a way around that passively. Perhaps it would be possible with a quad gang pot, but I am not sure if it is worth it for my purpose. :P I will chalk it up to resistive division limitation and leave it there. Perhaps someone who knows more than me can chirp in a simple addition that would minimize the effect I can't think of, but I am not sweating it.

Last edited by rich1051414; 16th April 2019 at 12:52 PM.
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Old 16th April 2019, 09:16 PM   #9
PRR is online now PRR  United States
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Question about channel balancing.
> the volume decreases towards 50%

Your sim-screen shows "10M" amp inputs. Assuming 10 Meg, that's unlikely. And pot value is not shown.

Assuming 10k pots and 20k amp input, yes volume will drop. Assuming 100k pots to 50k amp via a long cable, volume will drop appreciably and high-end response will fall below 20KHz, "warm".

There is actually a large body of writing about cross-feed. Particularly for headphones, but much of this applies to loudspeakers also. Have you harvested/plagiarized those who walked this field before you?
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Old 16th April 2019, 09:35 PM   #10
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Question about channel balancing.
me> Looks like the Panorama knob .... maybe Mac?

Darn organic memory. And I had that knob at-hand for much of a decade.

Crown IC-150. Dual linear BUT with center-tapped tracks AND some switching, probably to ensure no cross-feed at the extremes. After one try, _I_ always left it strictly Normal. But that rig's speakers were not much further apart than the IC-150 is wide.
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