Sola Sound Tonebender MK 1.5 Silicon

[Sparky]

Since silicon transistors work in the Fuzz Face / Tonebender circuits  I'm throwing this together.  Don't know which transistors to use and also not sure about the base resistor value.   The input cap could be a bit too high, too.    All in all it will be a modded FF.

[nocentelli]

Don't know which transistors to use and also not sure about the base resistor value.   The input cap could be a bit too high, too

Note that this is a positive ground (or "negative power") circuit using PNP transistors. Most people have a large stash of NPN and far fewer PNPs, and most people use a negative ground/positive power supply, so I would suggest flippng the power connections (i.e. +9v to the collector resistors and 0v/ground to emitters) and using npn transistors.

I'd try out any low-ish gain, npn BJTs you have to hand for the transistors. If you breadboard it first, you can swap out to see how (or if) different devices change the sound. If you don't have any at all, 2N3904 are cheap and widely available.

The 100k Q2-base-to-Q2-emitter is the standard FF value: Raising this value will reduce negative feedback and increase the perceived saturation. You could try a fixed 47k in series with a 250k pot or trimmer to fine-tune it to taste. The 4u7 input cap is quite large, but you could replace it with a 10n cap and add a 100k or 250k pot in series with the 4u7 and put that in parallel with the 10n ("input cap blend"), again maybe useful as an extra pot to tweak or as a trimmer to set and forget.

[iainpunk]

someone else, also called Iain, once told me to move the output cap over from in between the 470Ω and 8k2 to inbetween the transistor and the 8k2. this gives way more output level, if you seek that, or possibly if you add clipping diodes, way more satturation!

cheers

[Sparky]

Don't know which transistors to use and also not sure about the base resistor value.   The input cap could be a bit too high, too

Note that this is a positive ground (or "negative power") circuit using PNP transistors. Most people have a large stash of NPN and far fewer PNPs, and most people use a negative ground/positive power supply, so I would suggest flippng the power connections (i.e. +9v to the collector resistors and 0v/ground to emitters) and using npn transistors.

I'd try out any low-ish gain, npn BJTs you have to hand for the transistors. If you breadboard it first, you can swap out to see how (or if) different devices change the sound. If you don't have any at all, 2N3904 are cheap and widely available.

The 100k Q2-base-to-Q2-emitter is the standard FF value: Raising this value will reduce negative feedback and increase the perceived saturation. You could try a fixed 47k in series with a 250k pot or trimmer to fine-tune it to taste. The 4u7 input cap is quite large, but you could replace it with a 10n cap and add a 100k or 250k pot in series with the 4u7 and put that in parallel with the 10n ("input cap blend"), again maybe useful as an extra pot to tweak or as a trimmer to set and forget.

Yup, it's going to be npn.  It's pretty much a silicon Fuzz Face with different values.    I use a  Fuzz Face / Tonebender type test pedal with variable pots for everything as well as transistor sockets.
I've included a Vox Tonebender schematic that has different resistor values than the earlier Sola Sound version.  The lower value resistors and caps result in a pedal that has less bass and mush than the Fuzz Face.   That 47K base resistor cleans up the sound a bit while the 1K res. adds some volume.

[Sparky]

someone else, also called Iain, once told me to move the output cap over from in between the 470Ω and 8k2 to inbetween the transistor and the 8k2. this gives way more output level, if you seek that, or possibly if you add clipping diodes, way more satturation!

cheers

I'll probably keep it stock.  Thanx anyway!