Haze 67 Schematic

[Steben]

I think this is what you might look for:
(bias is set, only AC gain is changed)

[spoontex]

Why is there no Fuzz pot?

I had a look at the pedal and saw the controls are Volume, Fuzz, and the resistor rotary.

From what I can see the schematic in the thread isn't the same as the real unit.

No, it's not the same. For the photos that I see, seem that Haze change this resistor, because the resistors are in series with the 0.1uF cap.

[Rob Strand]

No, it's not the same. For the photos that I see, seem that Haze change this resistor, because the resistors are in series with the 0.1uF cap.

Yes, that's how I saw it.  The switch is bias shifting Q2's collector voltage.
(The resistor connects to the cap but they aren't *just* in series as you will find the 8k2 also connects to that point.)

[spoontex]

No, it's not the same. For the photos that I see, seem that Haze change this resistor, because the resistors are in series with the 0.1uF cap.

Yes, that's how I saw it.  The switch is bias shifting Q2's collector voltage.
(The resistor connects to the cap but they aren't *just* in series as you will find the 8k2 also connects to that point.)

But if I change beetwen resistors, I'm not going to also change the output volume?

[Rob Strand]

But if I change beetwen resistors, I'm not going to also change the output volume?

Yes, but I suspect that's what the pedal does anyway.   It's only changing two E12 resistor values so the jumps are small.

IIRC, one of the Fulltone fuzz-face pedals had a bias pot and it adjusted the same resistor as the Haze 67.   And yes, it does vary the output quite a bit.

The alternative is to vary the 8k2 resistor.   You will get less level variation in that case.    You should be able to step the 8k2 resistor and get the same set of Q2 collector voltages as varying the "divide resistor" to +V (the way the pedal does it now).

[spoontex]

But if I change beetwen resistors, I'm not going to also change the output volume?

Yes, but I suspect that's what the pedal does anyway.   It's only changing two E12 resistor values so the jumps are small.

IIRC, one of the Fulltone fuzz-face pedals had a bias pot and it adjusted the same resistor as the Haze 67.   And yes, it does vary the output quite a bit.

The alternative is to vary the 8k2 resistor.   You will get less level variation in that case.    You should be able to step the 8k2 resistor and get the same set of Q2 collector voltages as varying the "divide resistor" to +V (the way the pedal does it now).

I will build the two versions and compare them, but I think that I prefer the "no bias change" version.

[Rob Strand]

I will build the two versions and compare them, but I think that I prefer the "no bias change" version.

Experimenting is the best way to do it!   Everyone is different.  I had a 2 position bias shift switch on a few of my FF-like circuits and I liked the option but I'm not really a typical FF user.