Foxx Tone Machine clean blend. is it possible?

[fragmenterelec]

How difficult/possible is it to implement a fully clean blend into a Foxx Tone Machine circuit? I've clocked maaaany hours the last couple days trying what blend circuits the internet has to offer and nothing has worked completely right. The two recurring issues are:


- blend side is dull, not fully isolated from fuzz side
- fuzz side sounds suuuuper weak and sounds like 40-60% of it's full glorious self


Being the vintage circuit it is, my main guess as to why all these blend circuits haven't done-the-damn-thing would be the notorious aversion to input buffering that vintage fuzz circuits (apparently this one too) can have.

Is it possible to somehow not buffer the front end of the fuzz side while providing a solid clean blend OR is there some kind of signal isolation/splitter/blender circuit or clean blend tapping point that can provide the high impedance input the that the fuzz wants?

[idy]

I am thinking the first transitor with all its feedback network already too far gone to use as clean blend?

If so I would try a simple splitter/blender pedal. One side with the fox, the other your choice of clean boost. I build and use these handy things (with just two channels):
http://tagboardeffects.blogspot.com/2010/11/jfet-parallel-looper.html

the signal will still be buffered before it hits the fox. If that bugs you maybe add "pickup simulator" or tone suck knob.

[idy]

Maybe just build an Ampeg scrambler. Only downside is it is not a "fuzz booster" but rather a "fuzz blender" adding (padded) fuzz to a clean through.

[MikeA]

Didn't Jack Brossart (Prescription Electronics) do something similar around 1995 with the Clean Octave Blend?  I think he split it after Q2 into a clean side and an octave side.  The COB input didn't seem very picky about what was in front of it, it worked anywhere in the signal chain IIRC.  Mike

[fragmenterelec]

I am thinking the first transitor with all its feedback network already too far gone to use as clean blend?

If so I would try a simple splitter/blender pedal. One side with the fox, the other your choice of clean boost. I build and use these handy things (with just two channels):
http://tagboardeffects.blogspot.com/2010/11/jfet-parallel-looper.html

the signal will still be buffered before it hits the fox. If that bugs you maybe add "pickup simulator" or tone suck knob.

http://www.muzique.com/lab/pickups.htm

^^^ this. 

What I ended up doing is buffer the input, split the signal into fuzz/dry, then added that pickup simulator circuitry on the front end of the fuzz side using the secondary winding of a TM022-R transformer and grounding the primary.

- buffered input and output
- clean blend (clean to slightly dirty boost circuit)
- FTM side sounds normal
- is as revoltingly gnarly as intended

There is a bit of an issue with certain extreme settings resulting in high pitched feedback, however.

Is this topology too good to be true?

[bushidov]

It might be possible to add a parallel LPB-1 style circuit to it and "mix" it back in with 2x 10K resistors like moosapotamus did with his 360 Bass Fuzz. See his site with schematic here and look for his revised/modded schematic half way down the page:
http://moosapotamus.net/ideas/acoustic-360-bass-fuzz/

I noticed the idea works on my Big Muffs, giving them a clean blend, which actually is more like a clean injection than a blend, but when I tried the idea with a Fuzz Face, that didn't work so well.

[duck_arse]

.... then added that pickup simulator circuitry on the front end of the fuzz side using the secondary winding of a TM022-R transformer and grounding the primary.

fragmenterelec - as no-body else has yet said it, welcome to the forum.

why ground the transformer, and how, exactly? the Q1/Q2 combo has filtering about it that is meant to reduce the highs to allow better octaving, as I understand it, but, you might be able to pick a signal from the emitter of Q1 to feed forward as your "clean", with resistor mixer etc.

[fragmenterelec]

.... then added that pickup simulator circuitry on the front end of the fuzz side using the secondary winding of a TM022-R transformer and grounding the primary.

fragmenterelec - as no-body else has yet said it, welcome to the forum.

why ground the transformer, and how, exactly? the Q1/Q2 combo has filtering about it that is meant to reduce the highs to allow better octaving, as I understand it, but, you might be able to pick a signal from the emitter of Q1 to feed forward as your "clean", with resistor mixer etc.

Not sure if it needs to be grounded, but figured it was good practice to ground the unused side. Curious if that has any real practicality here?

Tapping the emitter of Q1 sort of works, but the signal was too muffled to get a totally usable clean. The emitter of Q2 gives a much louder and gained out feed, but still not at all clean.

Seem to have addressed the high frequency squeal by adjusting the emitter bias on Q3 feeding the clipping stage. Everything seems to work now!

EDIT: Thank you!

[Ripthorn]

I am thinking the first transitor with all its feedback network already too far gone to use as clean blend?

If so I would try a simple splitter/blender pedal. One side with the fox, the other your choice of clean boost. I build and use these handy things (with just two channels):
http://tagboardeffects.blogspot.com/2010/11/jfet-parallel-looper.html

the signal will still be buffered before it hits the fox. If that bugs you maybe add "pickup simulator" or tone suck knob.

http://www.muzique.com/lab/pickups.htm

^^^ this. 

What I ended up doing is buffer the input, split the signal into fuzz/dry, then added that pickup simulator circuitry on the front end of the fuzz side using the secondary winding of a TM022-R transformer and grounding the primary.

- buffered input and output
- clean blend (clean to slightly dirty boost circuit)
- FTM side sounds normal
- is as revoltingly gnarly as intended

There is a bit of an issue with certain extreme settings resulting in high pitched feedback, however.

Is this topology too good to be true?

I don't know if it's too good to be true, but I've had precisely this on my "to-build" list for a while. Sounds like it generally works, so I'll have to give it a go after finishing up the massive beast on my (7) breadboards.

[Ripthorn]

.... then added that pickup simulator circuitry on the front end of the fuzz side using the secondary winding of a TM022-R transformer and grounding the primary.

fragmenterelec - as no-body else has yet said it, welcome to the forum.

why ground the transformer, and how, exactly? the Q1/Q2 combo has filtering about it that is meant to reduce the highs to allow better octaving, as I understand it, but, you might be able to pick a signal from the emitter of Q1 to feed forward as your "clean", with resistor mixer etc.

Not sure if it needs to be grounded, but figured it was good practice to ground the unused side. Curious if that has any real practicality here?

Tapping the emitter of Q1 sort of works, but the signal was too muffled to get a totally usable clean. The emitter of Q2 gives a much louder and gained out feed, but still not at all clean.

Seem to have addressed the high frequency squeal by adjusting the emitter bias on Q3 feeding the clipping stage. Everything seems to work now!

Care to share the resulting bias setup for Q3? Curious minds and all that

[fragmenterelec]

Oh the normal bias of 1k to ground should work just fine, I just had  a trimmer on the emitter to play around with biasing and it was set too far to one side (around 1.5k).

[duck_arse]

I am a dope sometimes - of course the Q1 E will be clean, but also less than unity. won't go to well with the final output.

Not sure if it needs to be grounded, but figured it was good practice to ground the unused side. Curious if that has any real practicality here?

erm, no, not good practise. I'm not sure the effect on an inductors inducting when used as a dual-winding inductor, but on a transfowmer connection, you'd have a very bad short condition.

[fragmenterelec]

I am a dope sometimes - of course the Q1 E will be clean, but also less than unity. won't go to well with the final output.

Not sure if it needs to be grounded, but figured it was good practice to ground the unused side. Curious if that has any real practicality here?

erm, no, not good practise. I'm not sure the effect on an inductors inducting when used as a dual-winding inductor, but on a transfowmer connection, you'd have a very bad short condition.

fixed! thanks hahah. first time using only one half of a transformer guy here.