Question about the Ruetz rat mod

[stratcat]

There is a variation on the Ruetz that replaces the resistor that is typically lifted with a 1k trim pot.

Am I crazy or is this serving exactly the same function as the Zendrive voice control???

i.e less resistance equals more bass and less gain and more resistance equals less bass and more gain.

Also What would be good values be for a single RC network that doesn't cut bass like the original thin sounding circuit?

[slacker]

Yeah they are the same thing, you've got the function wrong though, it's basically the opposite way round.
The size of the resistor sets the amount of gain, so less resistance = more gain, it also sets the frequency response, the cutoff frequency goes up as resistance decreases. So as resistance decreases higher frequencies get boosted more, it's a treble booster.

As for values it depends what you want, increasing the size of the cap will boost lower frequencies more, which sounds like more bass, but it will be more distorted so might sound flabby or muddy or whatever. Making the resistor bigger boosts treble less, which sounds like more bass, but the bass won't be any more distorted.

[Frances Rhodes]

hi everyone

i have a technical question about the ruetz mod.

i understand it is supposed to change the cutoff frequency of the filter network formed with the capacitor, but it seems that this mod (replacing the resistor by a larger pot) is specific to the rat circuit.
like for the tube screamer for instance. we can see a similar high pass network (except there is only one there instead of 2 for the rat) and every article i read about opening the frequency to allow more bass in said to change the capacitor to a bigger one and not change the resistor. so i was wondering if changing either component had the same effect.
regarding the ruetz mod for the rat, i know a 1k pot is a very small value compared to the 100k distortion pot, but does changing the resistor instead of the capacitor also changes the gain of the op amp stage?

[ashcat_lt]

I'm pretty sure the answer is in the post just above.  The resistor does affect the total "passband" gain of the opamp AND the cutoff of the filter.  The cap changes the cutoff only.

[Frances Rhodes]

damnit, you're right! it was written just above and this topic couldn't be any shorter...

thanks for answering my really dumb question (and sorry)!!