Tone vendor bender mk2 bias

[Rimgrot]

Hi!
I'm currently building a Tone Vendor mk2. Bought a transistor set from Smallbear which came with the following components:
Q1 2n1305 - hfe: 67, leakage 40
Q2 OC75 - hfe: 70, leakage 270
Q3 2n1305 - hfe: 103, leakage 10

Smallbear suggest the following bias resistors:
R3 100k (R5 on the tone vendor pcb)
R4 91k
R6 6.2 k (R7 on the tone vendor pcb)

I have breadboarded the circuit and It works, but output volume is a bit low, about unity gain with the volume pot maxed. And the fuzz sounds undefined and gated/little sustain with attack pot on max.

The collector voltages with 9v power supply are:
Q1 c 8,29V
Q2 c 0.178V
Q3 c 8,7V

Is it possible to bias this circuit better? I have not tried any other Tone Bender circuits before so I am a bit unsure what I am aiming for and how it should behave.
Thanks!

 

[traumprinz]

"From my experimentation with MKII Tone Benders, Q1 doesn't need high gain and high leakage."

It's less about what Q1 needs and more that the combination of Q2/3 here will not bias correctly. There are tons of ways to bias these, but OP's will bias poorly without that change or large resistance tweaks.

I do think 60-90 hfe, ~200-300uA of leakage is most accurate to what you're likely to measure for OC75s, and thus, what you'd find in original OC75 units.

You can get by better with lowish leakage in Q1 with the 100K resistor on Q1 base. That's what was in the OC81D MK2s and appears to be what SBE suggests. OC75 loaded ones had 10K there and you may have trouble getting low leakage types to bias with that.

"Raising the voltage that high from -4.5V in a Fuzz Face, conversely, can only be achieved by lowering resistance to the collector"

There are many ways to achieve that. Higher Q1 beta, more Q1 leakage, higher emitter resistance, less Q2 leakage, lower feedback resistance, will all also increase the Q2 voltage. You can achieve it in a FF with stock values.

 

[andare]

I don’t think the transistor cares how you get it the voltage. 8vDC is 8vDC no matter how you slice it.

Is the implication here that leakage biasing is different from changing the bias with resistance?

Just what I noticed on my breadboards but you guys know more than me. Or rather I know nothing and you guys actually have knowledge.

 

[andare]

It’s not a knowledge thing, right?

Voltage is voltage. You were likely hearing the influence of something else.

Transistors don’t care if leakage or resistance gets them to a certain bias voltage.

I didn't know that. See That's what I'm talking about. I still don't know what transistors do and what biasing is, I just know they make fuzz.