Overdrive/Gain Pots

[GuyB]

DIY Zen type drive pedal, currently I'm using a 500K linear pot, but the Overdrive/Gain is too high for my preference, I'm trying to get less Overdrive/Gain, but have more control, so I can add smaller increments of Overdrive/Gain.

I don't want to purchase too many pots for these experiments, so what pot value do you suggest?

[nocentelli]

250k would give 0-50% of the original gain range, 100k would only give you 0-10%.

[GuyB]

250k would give 0-50% of the original gain range, 100k would only give you 0-10%.

Many thanks, that's very helpful info and will save me a lot of time and expense.

Thanks again.
Guy

[slacker]

As it's a linear pot you can get a rough idea what pot to replace it with just by turning it to where you get the maximum gain you want and multiply that by 500. Eg. You turn it about half way use a 250k pot, a quarter use a 100k.

Edit: beaten to it.

[Mark Hammer]

The gain is given by the feedback resistance in proportion to the ground leg resistance.  It will be easier to replace a fixed resistor value on the ground leg than it will be to replace a pot.  Increase that resistor value by 2-3x, and you will reduce the maximum gain and improve the dialability of the gain pot .

[samhay]

The gain is given by the feedback resistance in proportion to the ground leg resistance.  It will be easier to replace a fixed resistor value on the ground leg than it will be to replace a pot.  Increase that resistor value by 2-3x, and you will reduce the maximum gain and improve the dialability of the gain pot .

That's true, but the Zen drive also has a smaller 'bass' pot in series with the ground leg resistor, so you would need to increse this pot and decrease the cap...

I suggest the OP try a log pot. This way you have more control over the lower gain settings, but can still crank it when necessary.

[Mark Hammer]

The gain is given by the feedback resistance in proportion to the ground leg resistance.  It will be easier to replace a fixed resistor value on the ground leg than it will be to replace a pot.  Increase that resistor value by 2-3x, and you will reduce the maximum gain and improve the dialability of the gain pot .

That's true, but the Zen drive also has a smaller 'bass' pot in series with the ground leg resistor, so you would need to increse this pot and decrease the cap...

I suggest the OP try a log pot. This way you have more control over the lower gain settings, but can still crank it when necessary.

Also true, but the stock circuit has a bass rolloff around 1600hz and a max gain of 500x, when the Bass control is set to min.  Increasing the 1k fixed resistor to, say, 3k3, will drop the max gain to around 152x, and make the bass roll off around 480hz at its "thinnest".  If you're okay with that, then swapping out the one resistor will fix the problem.  If one wants a bit greater range in adjusting bass, then 2k7 will bring the bass rolloff up as high as 590hz, and set the max gain at 186x.

If push comes to shove, and GuyB can think of a reason to need a thinner and less grainier sound, then I suppose the cap value can be dropped to .047uf, and the resistor upped to 3k3 again.  That will produce bass rolloffs ranging from 1026hz (which is still thinner than a stock TS) to 254hz, with a max gain of 152x (38x at max bass).