SOLVED Soul Vendor - gated sounds

[ReinoutVrijhoef]

Hi everybody,

I'm quite new to pedal building, the Soul Vendor is my 8th endeavour. The behaviour of the pedal is not as I expected, so I would like to ask you for help. You can watch and hear the pedal on Youtube:

I recorded the video with a Strat in the bridge position running into a Kemper with a fairly clean profile of a Marshall Bluesbreaker, like, why not? The input on the Kemper isn't clipping, and the pedal behaves just the same on my tube amps.
I bought this pedal in a kit from Musikding, including a special set of AC125's, matched for a ToneBender mk3. The battery is running on 9.32V, the temperature is on room temperature (19°C, 66°F) and the humidity is about 57%. I haven't checked the hfe myself, because my cheap multimeter is being an *ss about it.





My circuit looks like this, you can find the schematic here.


If you can help me fixing this pedal, I would be very grateful. I can't seem to find the "right" voltages for the germanium transistors. I already built the Analog Sun (PCB Mania) which sounds great! Also the Rift (Aion) is a great sounding fuzz. Any help is greatly appreciated!

 

[Cybercow]

Thanks for your reply. R4 (10k) and R5 (3.3k) are on the emitters of Q1 and Q2, what will their effect be on the sound or the behavior of the transistors? I already have a trimmer on R7, do you mean R8 perhaps?

I mentioned R4 & R5 as the other two points for potential additional trimmers. On the emitter side.

 

[ReinoutVrijhoef]

You might want to check it - for russian diodes, the stripe almost always marks the anode. AFAIK the ones with a single blue stripe follow this standard (stripe = anode). I'm sure there's some variation, so maybe yours is an exception?

(This is also assuming the board you have in front of you matches up with the image on the webstore).

I have a D9E diode in there, it has the blue stripe on the right, according to the board. On the link here it's said, these diodes have the stripe on the cathode: https://www.pedalhackerelectronics.com/D9E-Russian-Klon-germanium-diode-p/d9e-10.htm. One this site (https://guitarpcb.com/product/germanium-diode-d9e/) the description is the other way around.

Now I'm confused. When I test the diode in circuit, I get a reading of 167 with the red lead on the striped side. What's going on here? Are all my diodes, also in the King Centaur (which sounds good) wrong?

 

[ReinoutVrijhoef]

I mentioned R4 & R5 as the other two points for potential additional trimmers. On the emitter side.

Yes, thank you. What will adding trimmers (changing the R value for that matter) do to the sound?

 

[mdc]

I have a D9E diode in there, it has the blue stripe on the right, according to the board. On the link here it's said, these diodes have the stripe on the cathode: https://www.pedalhackerelectronics.com/D9E-Russian-Klon-germanium-diode-p/d9e-10.htm. One this site (https://guitarpcb.com/product/germanium-diode-d9e/) the description is the other way around.

Now I'm confused. When I test the diode in circuit, I get a reading of 167 with the red lead on the striped side. What's going on here? Are all my diodes, also in the King Centaur (which sounds good) wrong?

I'm not familiar with the King Centaur (I assume it's klon centaur-adjacent?), but if it's using the diodes for clipping then it isn't going to matter if you're flipping the anode and cathode (especially if there's a pair of them).

The Ge diode in a TBMKIII is helping to bias Q3, so its doing a different job. I'd flip it and see what happens.

 

[mdc]

I've never seen a russian diode with the stripe on the cathode, though I could absolutely be wrong about that. I would guess that the pedalhacker listing is a typo.

 

[ReinoutVrijhoef]

I'm not familiar with the King Centaur (I assume it's klon centaur-adjacent?), but if it's using the diodes for clipping then it isn't going to matter if you're flipping the anode and cathode (especially if there's a pair of them).

The Ge diode in a TBMKIII is helping to bias Q3, so its doing a different job. I'd flip it and see what happens.

Dear mdc,
Thank you for your reply. I think you're correct. I checked the schematic of the King Centaur, and in that pedal the diodes are in symmetric clipping, so orientation is not an issue. I guess I never checked the polarity and just assumed I was right. And I was not. So my apologies for not accepting your input before, I will try to flip the diode and see what happens then.

 

[mdc]

No need to apologise! It's frustrating stuff when "standards" aren't standard. Hopefully that solves the gating issue.

While you're poking around in the pedal you could try to socket a few of the components and play around with values from other versions:

TONE BENDER MKIII: Component Values Table

TONE BENDER MKIII COMPONENT VALUES TABLE & SCHEMATIC FOR DIY GUITAR EFFECTS

vero-p2p.blogspot.com

You might prefer the MKIV bias values more than the MKIII? Or try some of the D*A*M variants? If you've already got it pulled apart, might as well have some fun with it.

 

[ReinoutVrijhoef]

I made another video of the pedal today, the gated behaviour is no longer there. A big thank you to mdc for pointing that out. I brought the pedal back to its original state (R6 and R7), maybe I'll play around with these values later. Is the sound of the pedal right now a bit like a Tonebender mk3? I never owned one, but this seems like a lot of gain from a "vintage" fuzz, see this video on YouTube. Edit: the ticks are digital, stupid me didn't sync the s/pdif clock...

These are the current voltages. For Q1 and Q2 they are on the low side, Q3 seems to be in range.

 

[andare]

I made another video of the pedal today, the gated behaviour is no longer there. A big thank you to mdc for pointing that out. I brought the pedal back to its original state (R6 and R7), maybe I'll play around with these values later. Is the sound of the pedal right now a bit like a Tonebender mk3? I never owned one, but this seems like a lot of gain from a "vintage" fuzz, see this video on YouTube. Edit: the ticks are digital, stupid me didn't sync the s/pdif clock...

These are the current voltages. For Q1 and Q2 they are on the low side, Q3 seems to be in range.

View attachment 45061

Sounds great to me. Who says vintage is low gain? Higher hFEs don't always give more distortion anyway.

All the voltages are equally on the low side (should be -3.5, -3.5 and -2) but often they are measured with new 9V batteries and those read above 9V, PCBs measure below because of power supplies and the protection diode