Am I crazy (part question)

A balance pot has 4 decks.

The heck? Okay, what you're saying makes no sense to me, so I'm going to go off on a limb here and make some wild guesses. Rein me in if this makes no sense.

I think that you may be thinking about balanced vs. shared-ground drive. If so, know that this should be irrelevant to potentiometers. A stereo potentiometer controls two potentiometers such that they have identical values (within tolerance) for a given setting of the control. The two are discrete and not linked in any way unless you make a connection between the contacts yourself. It is possible that one or more of the potentiometer contacts will be wired to ground - this is irrelevant to the operation of the potentiometer itself. In a balanced scenario, you would simply wire the contact designated for the left channel to left ground and that for the right channel to right ground, instead of both to a shared circuit ground. The pot itself doesn't know or care what you're connecting it to.

If you mean balance in the way of variable L/R volume amplitude, these can effectively use a normal i.e. non-stereo pot. You have some normalized value which you can spill back and forth between two poles, which is exactly what a standard (two poles plus center tap) potentiometer does.

A balance pot has 2 decks, a balanced pot has 4 decks :)

Of course, a balanced balance pot has 4 decks, but I haven't really seen any of those.

Quote:

Originally Posted by johnwmclean 

A balance pot has 4 decks.

 

Gimble: a balanced amp requires a 4 deck pot unless you're using two 2 deck pots.

 

Quote:

Originally Posted by gimble 

The heck? Okay, what you're saying makes no sense to me, so I'm going to go off on a limb here and make some wild guesses. Rein me in if this makes no sense.

 

I think that you may be thinking about balanced vs. shared-ground drive. If so, know that this should be irrelevant to potentiometers. A stereo potentiometer controls two potentiometers such that they have identical values (within tolerance) for a given setting of the control. The two are discrete and not linked in any way unless you make a connection between the contacts yourself. It is possible that one or more of the potentiometer contacts will be wired to ground - this is irrelevant to the operation of the potentiometer itself. In a balanced scenario, you would simply wire the contact designated for the left channel to left ground and that for the right channel to right ground, instead of both to a shared circuit ground. The pot itself doesn't know or care what you're connecting it to.

 

If you mean balance in the way of variable L/R volume amplitude, these can effectively use a normal i.e. non-stereo pot. You have some normalized value which you can spill back and forth between two poles, which is exactly what a standard (two poles plus center tap) potentiometer does.

Yeah, you'd have to be a bit clever to do a balanced balance pot.

Well, not that clever. You use a stereo pot again, you just hook it up differently.

Like Nebby pointed out, a balance pot is for controlling left to right balance.

For stereo, it is typically a 2 deck pot with a linear impedance taper.

A balance (linear taper) pot makes a weird volume control and vice versa. Volume pots are audio (log) taper 

The pot pictured may very well be a balance pot, Alps made linear pots for stereo balance application.

It is obviously not balanced (4 deck audio taper) though.

You can use a 2-deck pot to attenuate a stereo balanced signal.

I guess an alternate way of saying this is that you can use a 1-deck pot to attenuate a single balanced signal.

Ignoring the obvious benefits to availability & cost there are a couple ways to argue that its preferable to a 4-deck pot. Perhaps the largest is that there are no readily available pots (not steppers!) that guarantee the matching of any 2 decks to better than 1db. 

see dsavitsk's post here

You could also use a 2-deck balance pot as a balanced balance pot using mostly the same method.

That matching issue sounds like a job for some transistors...

Quote:

Originally Posted by stew1234 

So clearly a balance pot would in no way be acceptable for sure as a stereo volume pot. 

This is correct.