Fuzz Face with two band tone control

[soggybag]

Here's a Fuzz Face with a James tone stock. I wanted to try and get a little tone shaping out of the classic circuit. I tried two different tone circuits.

The first used an idea from the Stompboxology news letter. Described as an "aggressive tone tone control with 30db of boost and cut". It works pretty good but required a wah inductor which was awkward to source and fit on the board.



The second version used the James Tone control. A two band tone control similar to what's found on Orange, Ampeg, and Matamp amplifiers. This worked well, it had more parts but, they were all easy to source and place.



Here is a demo: https://youtu.be/WjGP4PGRv5A

http://www.super-freq.com/the-sultan/

[mozz]

Has anyone tried to use a emitter follower driving the tone stack?  Opps, didn't see the first one.

[antonis]

Don't know which is "the forst one" but there is NO Emitter follower in both circuits..

Maybe you refer on BJT based gyrator for inductor simulation, which isn't present in above schematic....

[soggybag]

I tried the gyrator but couldn't get it to work. The treble control would work but the bass control had no affect. I think it has something to do with the lack of resonance in the gyrator.

The version with the inductor worked no problem and sounded pretty good.

Here's a picture of the version with the gyrator:

[antonis]

I tried the gyrator but couldn't get it to work.

I can recall it, Mitchell..
(unfortunatelly without any issue fixing proposal..)

@mozz: Tonestacks don't like neither to be driven by high impedances nor to drive low impedances..
In Mitchell's Sultan v3, Q2 output can hardly be considered of low impedance as well as Q3 stage can hardly be considered of high input impedance..
(but, mutatis mutandis for particular Tonestack, they could be considered good standing..)

[soggybag]

I tried the gyrator but couldn't get it to work.

I can recall it, Mitchell..
(unfortunatelly without any issue fixing proposal..)

@mozz: Tonestacks don't like neither to be driven by high impedances nor to drive low impedances..
In Mitchell's Sultan v3, Q2 output can hardly be considered of low impedance as well as Q3 stage can hardly be considered of high input impedance..
(but, mutatis mutandis for particular Tonestack, they could be considered good standing..)

@Atonis give some of your insights. Do you think what I have is working well? It's sounds good enough. The tone stack is working.

I had an issue where it was sounding thin and brittle if I put a buffered effect in front. I think this was the classic Fuzz Face problem.

I'm a beginner it's hard for me to calculate impedance. I figured the Fuzz Face is pretty loud so I figured it had enough output to drive the tone stack.

I added Q3 and used 10k on the collector and 4k7 on the emitter (might be different in the schematic) this seemed to give me about unity gain with the volume at 12:00. It felt about right.

[antonis]

I added Q3 and used 10k on the collector and 4k7 on the emitter (might be different in the schematic) this seemed to give me about unity gain with the volume at 12:00. It felt about right.

Quite right Mitchell ..

Q3 configuration gives a gain of slightly less than 2 [(10k//100k) / 4k7) so you have output unity gain for Volume pot set at 50%..
IMHO, Q3 configuration might work well but lacks both at gain amount (for recovery stage) and Collector quiescent voltage (narrow swinging margins hence small headroom)..
I'd make R14 = 100k and R11 = 2k2 for better Collector voltage setting (lowering input impedance a bit due to lowering Emitter resistor Base reflected value) or R11 = 1k and R10 = 4k7 for additional output better driving capability (further lowering input impedance to about 60k from about 80k of your initial design..)

P.S.1
Don't face "impedance" as rocket science..
Just sit at any point of interest and look around you..
All the paths to ground (DC or AC) should be considered in parallel (as various grounds should be considered as one common point), use capacitive reactance for caps (X_C = 1 / 2π*f*C) and replace Emitter values with their resistance multiplied by transistor current gain (the last only stands when your looking forward..)

edit: Just found something sligtly more complicated than above said.


P.S.2
I intenionally apply terms like "recovery stage", "quiescent point", "swinging headroom", "Base reflected resistance" e.t.c to make you further study about transistor amps..