I built the David Gilmour pedal discussed in
this thread.
Didn't you say I should *increase* this value though? Should I try decreasing it instead? Or just add a trim pot?
Didn't you say I should *increase* this value though?
Yes, R22 in your posted schematic (Kit Rae's R4), but 4k7 is quite large for this resistor when most other Muffs are 2k2 or 3k3.
Should I try decreasing it instead?
R22? Only if you want to INCREASE gain.
This is a good application for Robert's
TRIMMIT! You could then dial in the amount of gain you want.
I'd use a 5k trimmer, and then you can see how lowering resistance on the emitter increases gain.
The thread
Big Muff Ram's head 1973 "violet #4" vs Stomp 75 does indeed reference the Stomp '75 in the
Muffin Fuzz build doc:
ie R4 @ 4k7 in that thread
is Stomp '75, which is R22 in the Muffin Fuzz schematic posted in your OP of this thread.
If you
decrease R22, you will
increase the gain of that associated transistor.
For example; the Creamy Dreamer's first & clipping stages have NO emitter resistor for a very gainy result. To quote Kit Rae:
"
I found there was no limiting resistor mod, but the emitter resistors were removed in the first three stages. ... pulling those emitter resistors makes for a very high gain Big Muff "
Also note, that the collector resistors are quite big — R13, R18 and R11 @ 15k, further intensifying the gain.
I really like this following schematic from Kit Rae's website, it explains a lot about the Muff circuit;
check out the info about R22 on Q4 (R5 & Q1 in the Muffin Fuzz schematic) and the other emitter resistors (and collector resistors):
You could further reduce overall gain of the circuit in a number of ways, but sticking with emitter manipulation for now, you could also check out:
KR / PPCB
R22 / (R5) = 100Ω
R21 / (R11) = 100Ω
R10 / (R16) = 100Ω
All of those are quite low, practically jumpered to ground, very high-gain. Increasing them to 1k each and...
Their corresponding collector values are as follows:
KR / PPCB
R13 / (R4) = 12k
R18 / (R10) = 12k
R11 / (R15) = 12k
...Decreasing all collector resistors to 10k ...
... might get you what you want without deviating too far from the inherent sound of the Stomp '75.
As mentioned before though, a little goes a long way — so maybe making those suggested changes to the emitter & collector resistors would soften the character of the circuit too much.
My recommendation would be to tune the entire circuit to what you like, and not worry about authenticity of achieving a purported Violet/Gilmour/whatever schematic's values. Tune to your gear, your fingers, your ears, the sound inside your head.