What's your favorite treble cut circuit?

[Bill Mountain]

This question is fairly simple.  I'm working on a rat-ish pedal and I dont love the filter control. I find it too dark.  So I have a simple request...please share your favorite simple tone control.  Something to cut the fizz without being too dark is ideal.

Thanks!

[Brisance]

Make R variable for extra points

EDIT: Honestly, on my last treble boosting overdrive pedal, I had a simple RC lpf for tone, worked a treat! IIRC it had 1k Pot as a variable resistor and I think a 15n cap, cant tell for sure, don't have the schematics here.

[GibsonGM]

For another option, you could look up "SWTC" or "Stupidly wonderful tone control", which gives a bit more 'usefulness' to the control.  It's all over this forum...

[Brisance]

Well of course that depends on the circuit in question, my variable LPF had little effect on overall volume, since it was feeding into the second gain stage, which had freq dependent gain the effect it had was to tame or leave harshness Also be sure to leave the top setting cutoff above audio range so it can be essentially disabled.

[Mark Hammer]

The SWTC is predicated on not having the buffering that the Rat includes, so it wouldn't be an improvement in this instance.

However, there is nothing to prevent you from altering the range of the Rat filter control, whether by swapping cap values, or the resistance range covered, or both.  Ultimately, it's just what brisance posted.

[Bill Mountain]

Does anyone have one that produces more of a shelving effect?

[Brisance]

OFF TOPIC( But I'm bored at work so I drew what I meant from memory, probably values differ quite a bit maybe layout also.  )

This provides very soft rolloff, without affecting volume:



Dont laugh too much at my mouse drawing skills 

[midwayfair]

Does anyone have one that produces more of a shelving effect?

Replace the pot with a jumper. Put the pot in series with the 3n3 cap -- just lift one end and wire the pot as a variable resistor -- and it's now a shelf filter. If you want to change the cutoff at that point, change the 10K that precedes the pot.

Jack Orman's version 2 of the SWTC will give you boost or cut, so you could also try that instead. I like that one a lot.

Brisance: That's the same tone control from the RAT, just with different values.

[Gus]

The rat one is a passive 1st order filter you might want a 2nd order filter or even higher order.

By the time you cut out the highs to your liking with a passive or active 1st order lowpass you are also in the upper mids thats why it is to dark

An active 2nd or 3rd order low pass should work better for you needs, you can select the response Butterworth, Bessel, Chebyshev

Do a search for "active lowpass filter design" or other strings of words

[Mark Hammer]

Good suggestion.  If a person is fine with a few presets, a 3-position DPDT on-off-on toggle can be used to select one of three 2-pole lowpass filter rolloffs.  As Gus rightly points out, shallower slopes require one to set the rolloff too low when attempted to eliinate fizz.  A 2-pole lowpass allows you to set the rolloff a bit higher, because the steeper slope eliminates more content above that rolloff point. 

For a fizzless distortion that can be set to bright and biting, round and vocal, or wolly and threatening, you might want to go with rolloffs at 4khz, 2khz, and 1khz, respectively.  You could do that with a pair of 3k9 resistors in series and a .01uf cap to ground after each.  The DPDT can then switch either nothing, another pair of .01uf in parallel, or a pair of .033uf in parallel.  That will get you rolloffs at 4080hz, 2040hz and 950hz, respectively; different enough from each other.

[Derringer]

I just made a fuzz based on the Karl Fuzz/Triple-Fuzz.

There's a C to B cap in there that I beefed up and added a variable 250K pot in series.
Highs were still a bit too high but going bigger on the cap darkened things too much ... like Gus said.

So further down the signal stream, I added a fixed LPF with a rolloff somewhere around 7Khz (I think).
But I figure that basically created a two pole system, first pole adjustable, and it worked out perfectly.

Maybe try something small like a 4k7 resistor with a 4700 pf cap to ground off of the source of the Rat's output buffer, see how that sounds in conjunction with the stock tone control and adjust your cap bigger or smaller from there.  If your design doesn't use the output buffer, maybe just drop a cap to ground from the resistor that's just ahead of the diodes and filter control.

[Bill Mountain]

Thanks.  I was thinking about something slightly different.  A fixed low pass filter (b/w 4k and 6k) and then a simple shelving filter.  I feel like the shelving style filters can reduce the fizz while maintaining some high mids.

The multi-pole filter is a good idea though.  I had thought for my next build I could do a variable active sallen key filter.

[midwayfair]

If you do this, you have a 2nd order shelf filter as it's turned down and a 1st order high-pass when it's turned up. I <3 controls that do two things.

47K --->----47K---->----Buffer
          |                |
        4n7            4n7
          \_________/
                  |
                100K
                  |
                 G

Values are just guesses.