Volume pedal pot values please

[Josh_bb]

Hi,

I have a very old (pot is dated 1957!) De'Armond volume pedal. the pot is a 1meg Linear.

I have always read that log was the way to go for volume pedals but this doesn't sound too bad ( apart from being a little worn), why is that?

the pot is located on the opposite side to regular wah pedals so I would have to source a decent reverse taper pot wouldn't I if i wanted to replace it with say a 250k pot?

any thoughts and tips would be greatly appreciated.

thanks

Josh

[willienillie]

If you want audio taper from CCW pot shaft rotation, yes you need reverse audio (anti-log) taper.  Which side of the enclosure the pot is on doesn't alone determine the direction of rotation, the rack can be on either side of the gear.  FWIW a typical Crybaby turns the pot CCW as you go toe down, so an audio taper would act as reverse audio, if you wanted to make it a volume pedal that gets louder towards toe down.

[Josh_bb]

FWIW a typical Crybaby turns the pot CCW as you go toe down, so an audio taper would act as reverse audio, if you wanted to make it a volume pedal that gets louder towards toe down.

thanks, so if i understand you correctly, a regular log pot would work okay my De'Armond as the pot is housed on the opposite site to a cry baby?

[willienillie]

If the rack is on the heel side of the pot shaft, like a Crybaby, then yes.

[Josh_bb]

here is a pic of one like mine (mine is older and has all metal gears) , the pot is on the opposite site than a cry baby...

[Mark Hammer]

First, are you seeking to replace it because it's not functioning properly, because the taper is unsatisfactory, or because you've heard that linear taper is "wrong"?

If the pot functions properly, then a 1M unit can be adapted to a non-linear taper by means of a parallel resistor.  See RG Keen's classic document about pots:  http://www.geofex.com/article_folders/potsecrets/potscret.htm

[PRR]

If you want modest change of gain, have other knobs in the system to set a happy gain and you only need a trim, linear works OK.

When you need a WIDE range of gain on one knob, audio taper gives you control in the turned-way-down zone.

It is very likely a LIN will be fine.

And much easier to find than rev-audio.

1Meg is likely to shave a lot of highs, depending how much cable it has to drive. 1Meg pot half-loud is 250k at the wiper. With 10 feet of cable, treble rolls off by 2KHz. This may even have been fine in 1957. Today 30-foot cables are cheap and now roll-off is 750Hz, near half the guitar muffled-away. 250k may indeed be a better value.

[R.G.]

It is quite difficult to design a priori a purely passive pot value for good frequency response AND good volume behavior on a volume pedal. The design requirements conflict.

The best easy solution is to buffer before and after the pot. This keeps things crystal clear and at the same time is substantially immune to cable loading. Buffering before and after makes the pot value almost irrelevant.

The problem with this is that old-guard guitaristas have conditioned the world to think that buffers are bad and that you'll suffer from non-passive guitar tone symdrome if you touch a buffer. That's non-existent of course, but still they'll try to convince you.

[thetragichero]

The problem with this is that old-guard guitaristas have conditioned the world to think that buffers are bad and that you'll suffer from non-passive guitar tone symdrome if you touch a buffer. That's non-existent of course, but still they'll try to convince you.

how much does a buffer improve this kinda thing? I'll tell ya
bought a broken volume pedal mainly for the enclosure. put an amz mosfet buffer on there and my non musician girlfriend talks about this thing like it has magical properties or something "when you press all the way down on it i can actually HEAR your bass!"
nothing special, just a buffer before it goes through a 20ft cable and into a di
only reason i don't make my pedals buffered bypass is that I'm lazy and true bypass is so simple

[Josh_bb]

the 1 meg pot seems to work fine which is pretty good considering it is date stamped as a CTS form 1957. but as mentioned things get dull sounding when you reduce the volume.

I was thinking about a 250k, but i wondered if I would need a funky taper as the pot is on the other side on this pedal.

Would a buffer kill the nice clean up effect you get on the fuzz face? I want to use a volume pedal rather than the guitar volume to do this

cheers

[highwater]

Would a buffer kill the nice clean up effect you get on the fuzz face? I want to use a volume pedal rather than the guitar volume to do this

Yes, but there are workarounds. You could add a pickup-simulator after the buffer, but then you would have the same problems as a passive volume on the output side. You could combine that with a buffer in the FF that's only active when the fuzz is *off*. That would stop treble-loss in your clean tone without changing the sound of the fuzz.

[ElectricDruid]

The best easy solution is to buffer before and after the pot. This keeps things crystal clear and at the same time is substantially immune to cable loading. Buffering before and after makes the pot value almost irrelevant.

The best not-quite-so-easy solution might be to use a VCA to control the volume, and then the pot only has to provide a control voltage, at which point the pot value isn't really so important and the cable length doesn't matter. And the overall lin/log response would depend on the control response of the VCA not just the pot (whether the VCA has a linear or exponential control characteristic).