Jimi Thing- Twin Face

[Synchrony Pedalworks]

Build Rating

5.00 star(s)

I have been super excited about this pedal. I loved the idea of having the aggressive and hairy of silicon transistors married with the sensuality of a germanium fuzz face. I also had the design idea for a while, but it took a while to get the parts together. The silicon transistors are BC108cs and the germaniums are OC44/CV7003 (Q1: 88hfe and Q2: 111 hfe). I biased by ear, and ironically, it measured near 4.5 V. I did get the germanium transistors from SmallBear and used their values for the resistors in the feedback loop and for the collector of Q1. Other than that, were no significant modifications. It is a fabulous pedal.

 

[andare]

What value did you use for the feedback resistor and why?

 

[szukalski]

Looks great! Love the silver and purple combination!

 

[Big Monk]

What value did you use for the feedback resistor and why?

I can’t speak to the value, but as to the why, the feedback resistor is a great place to tailor the gain of the pedal.

 

[andare]

I can’t speak to the value, but as to the why, the feedback resistor is a great place to tailor the gain of the pedal.

Yes i experimented with it quite a bit. I also added a pot in series like I'm the Fuzzolo for crazy tones.

I guess the value was changed to better match the transistors

 

[Synchrony Pedalworks]

Yes i experimented with it quite a bit. I also added a pot in series like I'm the Fuzzolo for crazy tones.

I guess the value was changed to better match the transistors

Correct. The values were selected to match the transistors.

 

[Synchrony Pedalworks]

What value did you use for the feedback resistor and why?

I think the value was 110k.

 

[Big Monk]

It's interesting that they would send a feedback resistor as a way to fine tune the bias. With that said, Small Bear's bias voltage choices have always been suspect to me with everything except Fuzz Faces.

It certainly has an effect but if you are using a trimmer for Q2 anyway, then the little bit of fine tuning you get from the feedback resistor is moot and you are simply changing the gain structure.

If you look at pedals that traditionally have higher feedback resistors (Colorsound One Knob Fuzz is the clearest example at 150k), they often tweak other parts of the circuit to compensate, i.e. the output resistor is usually lower, etc.

But, I'm rambling now. The important thing is that it sounds good in real life, rather than on paper!

 

[Synchrony Pedalworks]

It's interesting that they would send a feedback resistor as a way to fine tune the bias. With that said, Small Bear's bias voltage choices have always been suspect to me with everything except Fuzz Faces.

It certainly has an effect but if you are using a trimmer for Q2 anyway, then the little bit of fine tuning you get from the feedback resistor is moot and you are simply changing the gain structure.

If you look at pedals that traditionally have higher feedback resistors (Colorsound One Knob Fuzz is the clearest example at 150k), they often tweak other parts of the circuit to compensate, i.e. the output resistor is usually lower, etc.

But, I'm rambling now. The important thing is that it sounds good in real life, rather than on paper!

I appreciate the explanation. I am still learning the nuisances about fuzzes. I did not know the reason for that resistor change, but was trusting the source. I should have breadboarded the circuit to determine if changes were needed, but since it sounds great, I am not going to mess with it!

 

[Big Monk]

I appreciate the explanation. I am still learning the nuisances about fuzzes. I did not know the reason for that resistor change, but was trusting the source. I should have breadboarded the circuit to determine if changes were needed, but since it sounds great, I am not going to mess with it!

Absolutely. If it sounds good, leave it!