Transistor Specs for Tone Vendor Mk II?

[MobyOctopad]

Hi all, I've tried combing through old posts here, as well as on diystompboxes, looking for some guidance on gain and leakage specs for a TB Mk II build, and hadn't really had much luck other than finding out at least Q1 needs to be leakier than what you'd use in most other circuits. Until, that is, I read through the build docs for AionFX's Deimos where they recommend the following gain and leakage:

• Q1: hfe 50-100, high leakage (150-300 µa)
• Q2: hfe 50-100, low to medium leakage (100-200 µa)
• Q3: hfe 100-120, low to high leakage (50-300 µa)

Does this largely track with what folks have used on their TB MkII's? I'm particularly thrown off by such a broad range on Q3's leakage.

I was planning on paying an additional testing fee on some ge transistors and wanted to make sure something along these lines worked. Thanks y'all!

 

[Big Monk]

You don’t need that leakage that high on any of those positions. Anything over 20 micro amps in any position should be suitable as long as you don’t mind tweaking collector resistor values from the vintage values.

Pretty much any three transistors with gains of 70-120 hFE and leakage of at least 20 microamps will work in this circuit.

 

[Coda]

I think I remember shooting for 70/90/120. It’s equally important to socket the bias transistors.

 

[mdc]

I'd order this 5-pack, socket the transistors, and plug-n-play until it sounded rad:

Six Piece PNP Germanium Transistor Kit - For Classic Fuzz, Tonebender, Rangemaster Builds - JoeDocMusic

*In stock, ships from Maine, USA* JDM Pedals is now offering a selection of excellent quality, vintage PNP Germanium Transistors for your DIY Fuzz pedal build. These are the choice for "classic" Fuzz project builds, generally battery-powered, as they require a positive ground circuit. *We will...

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[MobyOctopad]

If I'm reading the schematic right, I could go with 70/70/100 hfe and just play with the values on R2, R5, and R7 to get the desired voltage, is that right? And would the voltage laid out in the Aion docs still be useful?

• Q1: Collector -8.5V, Base -0.05V, Emitter 0V
• Q2: Collector -0.15V, Base -0.07V, Emitter 0V
• Q3: Collector -8.5V, Base -0.15 to -0.35V, Emitter -0.1V

This is helpful, thanks y'all!

 

[Bobbyd67]

If I remember correctly Q3 should be leaky or else the circuit will sound a lot more gated and splatty at max guitar volume. That being said rolling off the volume knob on your guitar should clear that up, socket that Q3 and go for what you like best ^^

 

[mdc]

Those are normal looking TBMKII voltages but seriously don't get super hung up on any particular gain/leakage/voltage measurement. The original ones are all over the place and unless you're trying to do a forensic reconstruction of ONE particular pedal, just shoot for a pedal that sounds rad and you like playing.

 

[Guava13]

Those are good voltage readings to aim for. You can swap resistors to get there or go through a stash of transistors leaving the resistors stock.

 

[Big Monk]

Depending on the transistor, those collector voltages from Aion may be way too high and very gated.

I would shoot for anything over 8.00 vDC for Q1 and Q3 that doesn’t gate excessively. I also like to use values way lower than that for more sustain and more bloom but it gets noisy without a little gating.