Balance controls - how do they work?

[Daddy Dee]

One thing I've noticed, especially with vintage gear is that one channel is noticeably louder than the other, when the balance pot appears to be set in the center.

This is somewhat bothersome to me. Is there any reason for concern?

I just make the adjustments to make it sound right, but at times, this seems like so extreme a position on the pot that I am wondering it the amp will run at full power as set.

Is the position of the pot irrelevant here? If the channels sound balanced does that mean they are balanced regardless of the pot position? Sounds like a silly question, perhaps, but I am pretty non technical in my understandings.

Is this something that should or could be repaired?

Thanks in advance for your help.

[macaltec]

That's a good one. I can't help but am anxious to hear the answers you get. I have a tube pre that exhibits differences in balance relative to the volume position. Sometimes it is dead on other times it is shifted to one side or the other. Probably just a bad pot in my case.

[oldenough]

Good question, unfortunatly i don't have an answer, but like you i will be interested to see what the experts have to say. I have a couple of recievers that exhibit the same "problem"..

[Daddy Dee]

OK. Pretty common issue I think. hmmmm

bump

[Marvel]

Dee,

Balance pots, for gain are usually made up of two volume pots in one housing, with their taper rates opposite each other. The wiper on one of the pots could be dirty or worn, causing one side to always be a bit low.

Mark's Merlin uses two separate pots as gain controls to achieve the same thing, although the separates provides some diffeent functionality, as you can actually adjust gain independently on each channel.

Bruce

[Erik Mandaville]

Dee:

In addition to what Bruce indicated (the wiper is the output of the control, by the way...), there is the possibility that the off center position of the control (may) indicate some gain differences between the two channels of the stereo component. There are a number of things that can cause that, including tubes, themselves. Unless passive parts such as plate load resistors, bias resistors, interstage coupling capacitors etc. have been changed for new correct values according to the original design, some of the difference you see may be associated with that, and the balance control is simply doing its job -- balancing out the differences in gain in order to compromise.

If the balance control doesn't have a detent, you might be able to loosen the set screw on the knob of the control (if it has one, the pots might have splines or grooves, in which case you just pull the knob off and reposition it), and reposition the indicator so that it's pointing to the center or straight up. This is a sort of 'band-aid' solution for you own peace of mind, but if the amp sounds fine otherwise (is this the Fisher?), you probably don't need to worry about it. If the difference in channel balance is drastic, you might want to dig a little deeper into the source of the discrepancy.

What happens if you swap the output tube pair to the other side, driver tubes? does the balance shift in the opposite direction?

Erik

[chops]

Dee:

In addition to what Bruce indicated (the wiper is the output of the control, by the way...), there is the possibility that the off center position of the control (may) indicate some gain differences between the two channels of the stereo component. There are a number of things that can cause that, including tubes, themselves. Unless passive parts such as plate load resistors, bias resistors, interstage coupling capacitors etc. have been changed for new correct values according to the original design, some of the difference you see may be associated with that, and the balance control is simply doing its job -- balancing out the differences in gain in order to compromise.

If the balance control doesn't have a detent, you might be able to loosen the set screw on the knob of the control (if it has one, the pots might have splines or grooves, in which case you just pull the knob off and reposition it), and reposition the indicator so that it's pointing to the center or straight up. This is a sort of 'band-aid' solution for you own peace of mind, but if the amp sounds fine otherwise (is this the Fisher?), you probably don't need to worry about it. If the difference in channel balance is drastic, you might want to dig a little deeper into the source of the discrepancy.

What happens if you swap the output tube pair to the other side, driver tubes? does the balance shift in the opposite direction?

Erik

Hi Erik... long time! []

I was going to say something within those lines as you have already mentioned. I was also thinking that maybe there might be some caps that are out of spec or possibly dirty RCA connections.

I'd be inclined to go through the entire unit with some DeoxIT before replacing parts left and right. It just may very well be oxidized contact surfaces which run wild with older gear.

[Daddy Dee]

Thanks Guys. I appreciate the tutorial here.

Erik, Actually hadn't thought about swapping tubes to see if the issue follows the tubes.

I'll do that.

[Daddy Dee]

thanks Mark

[Groomlakearea51]

Also "poor" quality source recordings can be a problem; sometimes the recording is "biased", or was not balanced when made. I've noticed this on a number of poorer quality LP's and CD's. It shows up on the TASCAM unit all the time, and also on the 10" AKAI pro unit I had as well awhile ago. I fiddled around with a leveler once with a turntable and then adjusted the tracking, etc., but simply could not overcome either the left or right level being higher than the other without correcting during the recording. I also tried "flipping" the stereo "reverse" switch on my AU-999 one day and voila', crappy from the left was now crappy on the right.

[Daddy Dee]

thanks groomlake