Reversing pot taper?

[ashcat_lt]

So I'm building a volume pedal into a crybaby shell.  Using a 500K pot from a Les Paul, which I've modified using conductive paint so that it will actually go from 0 to 10.  This has reduced the overall resistance to somewhere around 380K, and I'm thinking of buffering on either side of the pot itself. 

Problem now is that the log taper pot turns the wrong way.  Starting from heel down it gets louder very fast up to about halfway and then the change is very subtle.  It really needs a reverse log pot, but I'm wondering if there's a relatively easy way to make it act that way.  I'm open to active solutions, as long as it doesn't get too complicated. 

Thanks guys.

[jasperoosthoek]

I needed a dual reverse log pot some years ago. Instead of reversing the taper I reversed the shaft. It worked but the shaft kept falling out of its socket.

But what I think you could also do is simply build a frame so it fits the other way around. Extruded aluminum L bar will do just fine and is easy to work with. Drill a few holes bolt it and you are done. You could then even salvage a wah pot. I haven't tried it but I think they are fairly logarithmic (S-taper???).

[amptramp]

[jasperoosthoek]

There are specialized gears for pot so they can be mounted to a 90 degree angle. But wouldn't mounting it the other way around be a lot easier .

[ashcat_lt]

^Might be if I had tools and/or mechanical skills. 

What turned out to be easiest was that I found out I had a 300K linear pot to spare in the same LP.  Painted it up (one of the things I sort of wanted to avoid) and it came out to 222K.  Put a 47K from wiper to ground and it works.  Seems it may actually have gone a little too far, but it might just take some getting used to.  I did end up with a buffer on either side, so the pot value doesn't make any tonal difference.

[skrunk]

yes, spontaneous buffer growth can be a problem with low pass pots.

[tubelectron]

Hi ashcat_lt,

Here's what I have done with success to make an active volume pedal in a CryBaby shell. It gives a progressive volume-control and doesn't loss the highs due to the lo-Z out (<10K) :



A+!

[edvard]

See R.G.'s article on pots:
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm

Scroll down 'til you get to the "Reverse Log" diagram.
With your 500k pot a ~100-82k resistor strapped across center to pin 3 (the clockwise-most pin) ought to do it.

[ashcat_lt]

tubelectron - does that go from all the way off to full volume?  Even with the fact that the way shell won't turn the pot all the way?

edvard - Believe me, I was there.  Since the 500K was log taper to begin with, I think the tapering resistor would just get me back toward linear.  (?)

[edvard]

edvard - Believe me, I was there.  Since the 500K was log taper to begin with, I think the tapering resistor would just get me back toward linear.  (?)

Ahh... there lies the rub.
I don't think you'll get linear again, but something like an "S-taper"

[tubelectron]

tubelectron - does that go from all the way off to full volume?  Even with the fact that the way shell won't turn the pot all the way?

Yes : the Fet amp is here for compensation to retreive exact full volume justly because the pot cannot go mechanically to its maximum travel when the treadle is down. And as the pot is settled to go to 0, then you have silence when the treadle is up.

A+!

[zombiwoof]

Why not just buy a CTS left-hand (reverse log taper) guitar pot?.   They're only $5, and you can get them in 250k and 500k.  Seems like the simplest solution to me.

Al