Taming treble response

[mysticaxe]

I've built a Tweedy Bird drive that is a lot of fun to play.  My only problem is that the treble is a little much.  The J201's are Fairchilds and biased to around 4.5-5V.  I'm looking for ideas where I can cut some treble from the circuit without changing the character too much.  Playing with the Tone Stack calculator doesn't seem like there is much flexibility in the treble side (at least beyond what is already in there).  Between Q4/Q5 and Q6, it looks like there is some additional filtering where R13, C13, and R15 form a low pass filter (based on my limited electronics knowledge).  I think if I lower R15, that should drop the treble across the board.  Am I right?

[midwayfair]

R13, C13, R14, R16, and C14 form a two-pole filter. You can increase either of the 10K resistors or lower R14 and you'll cut more treble.

You can also strap a small cap from the output to ground. It'll form a low-pass filter with R21. Shouldn't be too hard to find what you're looking for with a calculator.

If you want to cut treble before clipping -- this mostly applies to transients and line noise -- raise the 470pF cap at the input.

Any of these changes will kind of dull things at lower gain settings. I'd make them switchable.

[mysticaxe]

Thanks Jon.  I'll take a look at those parts of the circuit.  Strapping the cap would be really easy (if it works and sounds good) - wouldn't even need to take the board out of the box.

[mysticaxe]

So I think a 3n3 across the output (to ground) worked well to my ears on my home rig.  I'll have to solder it in over the next couple days and try it more in a couple rigs to see if that helps.  I think that may have saved the pedal.


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