best value for master volume pot

[motterpaul]

dang - i was just reading this today (someone provided a link but i cannot find it now) -

Sometimes an overdrive pedal will sound dull when you turn down the volume pot, but it comes to life again at a certain point as you turn it back up.

Why does this happen, and if you have a pedal board where you need to set a certain pedal at a certain volume and it sounds dead at that setting, can you substitute the volume pot with a different ohm value and have it sound better?

I seem to have this issue with a current build and i would like to try a different value. The one I have has 100k (mercury brunetti box) - so should i go higher or lower?  

[Travis]

It depends on the circuit. That's why circuits often use different values for the volume pot

[Beaker]

All you can do is try different values, and see what happens.

[Frank_NH]

As Travis said, it really does depend on the circuit.  I too have wondered why the ubiquitous 100K pot has been used as the volume control on so many circuits.  The answer is that the volume control, if it's the last element in the circuit, has to be  compatible with the impedance of the circuitry upstream as well as the load it's driving downstream.   For example, if you're circuit is pushing an amp with a 1M input impedance AND your circuit itself has an output impedance that's low (say 1K - 10K) then a 100K output control pot is a good compromise.   That's also why you sometimes see buffers in circuits before the output - they provide a low output impedance to the volume control.

[Travis]

Beaker wrote

All you can do is try different values, and see what happens.

Or if you're a hotshot you can calculate the output impedance of your circuit and choose a pot value and output cap value that will suit your needs

[motterpaul]

It was funny - i was working the brunetti which i had just boxed - so i didn't want to take it apart to experiment with different pots, and i was just reading a thread (I think at FSB) about the theory about volume pot values - so there are some guidelines, albeit maybe loose.

frank - i guess all the tl071s i had were fakes, because i found one in an old build and i borrowed it, and i noticed it had a small but different (orientation dot) marking - and it works.

So the particular circuit now is much better, but it still has a has a 'sine' wave squeal- but it goes away IF i turn my guitar volume down just a hair to literally 9-1/2. So, it does have to do with input (impedance, i guess). it is really funny that such a small change means i can literally turn the pedal volume up full.

Thanks all for answers.