Voodoo Lab Overdrive Gain Knob Not working correctly

[Hallmar]

Hello!

I just finished a Voodoo Lab Overdrive. The distortion itself sounds fine! But the problem is that the distortion doesn't work until the gain knob is at almost full or atleast 10/12 of it.

Anyone here who knows whats wrong?

The only modifications that i did was to lower R5 to 39k.

Here's the Schem.



Thanks in advance!

[Hallmar]

I found out what was the problem.

I'm using a Log potentiometer but the Schematic says to use Reverse Log potentiometer.

This is the third @#$%ing time that i've had problems with pedals because of Reverse Log Pots.
Is there any other solution than too buy it off ebay?

[R.G.]

Read Geofex. (http://www.geofex.com)

In this case, "The Secret Life of Pots".

[JebemMajke]

I found out what was the problem.

I'm using a Log potentiometer but the Schematic says to use Reverse Log potentiometer.

This is the third @#$%ing time that i've had problems with pedals because of Reverse Log Pots.
Is there any other solution than too buy it off ebay?

I'm using lin for gain. Gain all the way to the max. Kicks ass.

[Hallmar]

I found out what was the problem.

I'm using a Log potentiometer but the Schematic says to use Reverse Log potentiometer.

This is the third @#$%ing time that i've had problems with pedals because of Reverse Log Pots.
Is there any other solution than too buy it off ebay?

I'm using lin for gain. Gain all the way to the max. Kicks ass.

So the LIN works?

I'll order a 500k lin then!

[JebemMajke]

It doesn't matter if its lin or log or reversed log. When it's maxed it will sound the same. With lin gain starts at about 10 o'clock. And at 3 it's almost the same as if it was maxed. With reversed log gain would start at about 9 and would slowly increase until it hits max. So if you are like me, aka will keep it at max forever and ever, you can use which ever one you like. But if you want it to be as original and use it like a normal person you should get reversed log.

[Mark Hammer]

I've mentioned it on other threads here, but anytime the gain of an op-amp is set by the ground leg resistance (as it is with this circuit, and many others), you'll have the most "dialability" with a reverse-log pot.

I'll leave you to do the math, but consider that the gain is equal to [feedback resistance + total ground leg resistance] / total ground leg resistance.  here, total ground leg resistance is equal to R5 + current pot value.

When you do the math, you'll quickly see that it takes large changes in that resistance to budge from the lowest possible gain, to marginally higher gains.  Once that total resistance starts to get smaller, relatively small changes in pot resistance make for substantial changes in gain.  A reverse-log pot distributes those small changes over a larger arc of the pot's rotation than a linear or log pot will.  The circuit will obviously still work, regardless of the pot taper used, but the dialability of desired gain settings will be trickier.