Tubescreamer

[adding_to_the_noise]

Hi all,
I built a tubescreamer a while back, and then recently modded it. I can't seem to find the post i read back when i modded it to see what it was I had changed, but I want to change it back a little. It has a little too much treble in it now and I want to try and get a more even sound. I'll do my best to list the parts that I changed. If anyone can help me understand what each of these mods affected that would be great too. I'm going by the schematic at tonepad's website.

The capacitor on pin 2 of the IC changed from a .047 to a .1 and the resistor right after it to a 2.2k
RA is a 400 ohm i think
Replaced all tantalum with poly caps
The 51k near the diodes changed to 20k
changed one diode to a 1n4001

[slacker]

I don't think any of those changes should should have given it more treble, here's what they do.

The capacitor on pin 2 of the IC changed from a .047 to a .1 and the resistor right after it to a 2.2k

Changing the 4k7 to 2k2 doubles the amount of gain the circuit has, changing the 0.047 cap to 0.1 at the same time means the bass roll off of the stage stays at 720Hz. I suppose at the higher gain setting there might be some more treble, but if you turn the gain down it should sound the same as it did before.

RA is a 400 ohm i think

won't do anything noticeable.

Replaced all tantalum with poly caps

If they are exactly the same value this doesn't do much, it might change the sound slightly. If the values were  different then it might give a bit more treble.

The 51k near the diodes changed to 20k

This adjusts the minimum gain so it's the same using the 2k2 resistor as using the original 4k7 resistor off pin2.

changed one diode to a 1n4001

might change the sound of distortion a bit.

Hope that helps

[slacker]

Actually it could be changing the amount of gain that has done it.
The pedal now has double the gain so all the original sounds happen in the first half of the gain pot. So where maximum gain was with the pot set to 500k the same amount of gain is now with the pot set at 250k. The value of the Gain pot in parallel with the 51pF cap in the feedback loop of the first opamp stage make a low pass filter that reduces high frequencies above a certain point. With the pot set at 250k the frequency is twice as high as with it set at 500k, so for all the original gain settings you will have more treble in that stage than before the mods. I don't know how much difference that makes because the tone control section then removes some treble anyway.
To fix this you could change the 51pF cap to 100pF. If that was the cause of the problem it would make the original gain settings sound the same as before the mods, but it might make the new higher gain settings sound muddy.

[adding_to_the_noise]

cool, thanks for the input. I know this is a different subject now, but i don't like starting new threads for everything. I'm building an effect that i plan to have at the end of my effect chain which will have two switches. The first one will act as a regular stomp switch for the effect inside the box and the second to completely mute the whole chain. How would i do that without getting any buzz or hum from my amp? Switch the input to ground? maybe throw a resistor in there to reduce the pop on switching?