Tone Control ideas?

[Transistor-Transistor]

Finally got this distortion working and sounding great. I just can't decide what kind of tone control I want to use with it. It originally had a pot that would change the soft clipping intensity but it didn't do all that much and then I added hard clipping after the output boost stage which made that knob basically useless.



Soft clipping diodes are 1n34 and hard clipping diodes are 1n4148

I should also mention r10 is also 220k and not 10k

Right now it has a switch after the input buffer to change the cap value but I'm probably gonna take that out and have the 0.22uF fixed there.
Any thoughts, comments, or advice are more than welcome! I'm not a professional in the slightest and I want to learn as much as I can about all this.

[Elektrojänis]

It will depend a lot on what kind of tonal changes you are looking for in the tone control.

If you like the sound as is but want something to perhaps make it darker or brighter every now and then, the big muff tone control should be a good starting point. The usual part values give it a bit of a mid cut when centered but that can be flattened by tweaking the part values. For tweaking the par values and visualising what it does to the frequency response, you could take a look at Duncan's Tone Stack Calculator. It also has several other tone controls you can play around with.

[ElectricDruid]

+1 agree, good suggestion.

Have a play with a few of the other tone options available on that site while you're there, because the range of stuff available is really something else! 

[Zveeen]

I once built a fuzz circuit where I didn't want the tone control to change the hi end, instead just focus on the low end. What I came up with was a tone control that can either cut the bass or boost it kind of like a pultec eq.
I will also post two pictures with the response on both extremes of the tone knob.
Maybe that's the circuit you're looking for, Im always very picky with choosing the right tone control.

Regards

[Mark Hammer]

The amplitude of bass content, and wound-string content in general, is higher than that of unwound strings (well, unless you have your pickups adjusted very unevenly), bringing the low strings much closer to whatever clipping threshold there is than the unwound ones.  That's pretty much the modus operandi behind the Tube Screamer - attenuate the bass feeding the clipping stage and the clipping will be more consistent from lowest to highest note.

At the same time, distortion is something we like to insert for solos and such, reverting back to a (mostly) clean tone once the pedal has done its duty.  But the amp may be set to produce a nice bright clean tone, which can end up accentuating the added harmonic content from the pedal in an undesirable way.  What I know I generally aim for is a treble cut, or fixed filter, that can give me the pedal sound I want, irrespective of what the amp controls are set for, such that when I turn the pedal off, I get the clean rhythm sound I wanted.

These two considerations argue for two tonal adjustments: 1) a variable low-end control before the clipping stage, and 2) a variable treble cut after the clipping stage/s.

You kind of address #1 with your switch between C2 and C3, though I would perhaps make C3 a smaller "default" value (i.e., no switch), like 10nf, and put a 100k pot in series with C2, which would be a higher value, like 470nf.  This uses the very clever idea Joe Gagan implemented in several of his Fuzz Face variants, more than 20 years ago, to provide variable bass drive to the clipping, by means of a parallel path around the input cap to the clipping segment.

Control #2 would be some sort of treble bleed in parallel with your diode pair to ground.  Alternatively, if the output level of the circuit is high enough, consider using an SWTC-type control between the diodes and volume pot.

[Eddododo]

A lot of places to play with feedback to boost or cut frequencies..

It might be a good time to grab some EQ pedal, and single out frequencies to see what you love emphasized with this circuit

Another one guitarists seem to like is a high pass, which could be treated conceptually as a treble booster... again with the feedback available, you might not have a hard time squeezing in a high pass that has some resonance at the corner frequency... neat way to get a distinct sound. Something like a crude sallen-keye arrangement

[Rob Strand]

Maybe something wrong with your schematic.  Something look wrong around Q2, R6.  The base of Q6 needs as resistor.   As is it may still produce sound.   The lack of base bias might explain why R6 needs to be 220k.

[Transistor-Transistor]

Whoops haha. Yeah R6 is connected to the base on the breadboard. Thats my error on the schematic.

[Transistor-Transistor]

I like the idea of using an EQ pedal to find the sweet spot but uh, I don't have one. I'm thinking of doing the active tilt control thats on the website you guys recommended me. I haven't tried it yet because I'm wondering if theres a way I could connect it to a transistor instead of an Op Amp but I don't know if thats possible

[Rob Strand]

Whoops haha. Yeah R6 is connected to the base on the breadboard. Thats my error on the schematic.

Another thing is, as drawn, C4 is virtually connected in parallel with C7 via C6.  So you can replace C4 and C6 with a single cap, perhaps 10n at the C7.  (Depends on how the schematic looks after fixing R6.)

[Transistor-Transistor]

Oh yeahhh. Thanks Rob!

Here's the updated schematic

[Transistor-Transistor]

Now here it is haha

[Rob Strand]

Now here it is haha

Getting back to your original question, it's not really that easy to answer because voicing the pedal is kind of up to the designer.   Some people go for a simple low-pass filter but if you want a fuzz pedal type sound maybe that's not a good choice.  Perhaps a panning control something along the lines of a muff.  Also if you don't like the notched sound you might need to tweak the values to flatten out of the mid position.   

https://www.muzique.com/lab/tone3.htm

You will soon know if you like or hate it.   Although be aware the part values can make or break it sometimes.  That's where you need to play around a bit.   It's not uncommon to spend a few days playing around with values to fine tune something.  Perhaps even dumping the whole idea and trying something else.

[marcelomd]

Suggestion: If you don't have an eq pedal, you can try a DAW, recording software. Most of them have free eq plugins and amp+cab simulators.