Grapevine cap subs

[maysink]

I read somewhere on this board a 100pf should be changed to a 151pf. But which one should I change, C3 or C9? I'm guessing C9. ANyone care to confirm? TIA!

[maysink]

bumper

[madbean]

I believe that is referring to C9. Going up to 151pF will let a bit more high end through when the gain pot is turned down.

[maysink]

thx brian!

[madbean]

Or, is it the other way around....it's a high pass filter so it is probably more accurate to say a higher value there attenuates fewer low frequencies, so that there is a broader range of frequencies passing through at minimum gain.

[CRBMoA]

I would think at the 100-151 pf range, the differences should be nominal. But I'm just a bass player, so what do I know.

[madbean]

It's actually a difference of about 500Hz, so it's not insignificant. Actually, I'm struggling with this very thing on the "Rump Roast" project I'm about to release. It has a similar control with a 250pF bypass cap, which actually makes the thing incredibly bright in certain settings. By raising the value you can darken it down a bit, but then you have to balance that with it at full rotation (it's a tone control) where too high a value ends up removing a little bit of the 'wump' in the lower mids.

[CRBMoA]

You are just trying to get me to buy the circuit so I can try for myself...................

Actually, that does make sense. The change would not voice the pedal for bass, but it would affect the bottom end of the guitar, especially on the neck P/U.

I am here to learn.