Tone Vendor MkII

MichaelW

MichaelW

Well-known member
Ok this is the last of my "tasting flight" of fuzz builds.....(I'm too much of a lightweight to get through a wine flight or even a beer flight but I do enjoy the heck out of a bourbon flight.....but someone else has to drive....:))

I got the "right" trannys because I ordered a matched set from GuitarPCB. They measured a little differently on my tester than what was on the packages but it was close enough.

Here are the gains I used:
Q1 = 67
Q2 = 106
Q3 = 184

I built it stock........and I like it the least of all my fuzz boxes. I think there's something wrong with it but before starting a troubleshooting thread I figured I'd check in with my fellow fuzzologists to see if this is how it's supposed to sound.

1. Volume seems really low compared to my other fuzzes. Unity gain is around 2 o clock. All my other boxes 2 o'clock is "tear your head off" volume.
2. It feels like it's not biased properly (which may account for the above) but there's no bias trimmers. I'm thinking about installing some "Trimmits" if they ever get back in stock. Anything I should be trying to look for in getting the bias right?
3. It sounds harsh and "gatey", especially when I put a boost or compressor in front of it. When using a compressor, the note decays very quickly or the attack will have a very low volume then jump up. It's not the "creamy" sound I was expecting from a full Ge fuzz box.

I put all the fuzz pedals I've built so far out in a chain and have been going back and forth. The one that just sounds absolutely killer to me is the Marigold (Sola Hybrid Tonebender). Followed by the Ge side of my Twin Face, then the Acid Rain which sounds more like a hybrid distortion/fuzz pedal. All 3 boxes invoke song parts in my head that I will eventually try to record. The Tone Vendor Mk II just doesn't sound very good or sound quite right. But then I don't know what I don't know, maybe it's supposed to sound like this? Not sure if I should try some different transistors (All the PNP's I currently have are all really low HFE).

The build went really quick and smooth, low parts count and I actually DID have the right kind of sockets for this build. (I need to find some more!)

IMG_3052.JPG

IMG_3050.JPG

IMG_3053.JPG
 
The symptoms make it sound like a biasing issue. Did you measure voltages? Also is that a charge pump? Could it be that the chip is bad? It seems pretty common.
 
I tried swapping the charge pump, no change.

With the pedal off

At the IC:

Pin 1: 9.03
Pin 2: 5.17
Pin 3: 00.0
Pin 4: -3.74
Pin 5: 9.03
Pin 6: 5.63
Pin 7: 4.18
Pin 8: -8.91

Anode side of D100: 9.12
Cathode side of D100: 9.03

Pedal ON:

Q1 Collector = -8.88
Q2 C = -.353
Q3 C = -6.87
 
MichaelW said:
I tried swapping the charge pump, no change.

With the pedal off

At the IC:

Pin 1: 9.03
Pin 2: 5.17
Pin 3: 00.0
Pin 4: -3.74
Pin 5: 9.03
Pin 6: 5.63
Pin 7: 4.18
Pin 8: -8.91

Anode side of D100: 9.12
Cathode side of D100: 9.03

Pedal ON:

Q1 Collector = -8.88
Q2 C = -.353
Q3 C = -6.87
Click to expand...

Q1 is probably contributing to the gating. Dropping that between 7.8 vDC-8.0 vDC should fix that.

Dropping Q2 down to around 200 mV will raise Q3 voltage. My personal favorite spot is between 7.6 vDC-8.0 vDC.

If you have the transistors socketed, try a lower gain unit in Q3.
 
Your a freaking genius, I don't care what anyone says about your socks....:)

Ok, so I took out the old Q3 (184 hfe) and moved what was in Q2 into the Q3 (106 Hfe)
Then replaced what was in Q1 and Q2 with a couple of lower gain MP16A's (38 & 44 respectively).
It has definitely reduced the gating.

Here's a weird thing that maybe you can 'splain me. The pedal seems very sensitive to input gain.
The gating issue is much more prominent with a humbucker (which I used in all the clips). But this is greatly mitigated by putting a buffered bypass pedal in front of it. (E.g., my Klon).
I can't run a boost in front of it or the gating gets worse. Why is this?

As for next steps, I think Q3 voltage is still too high (it's at 7.71)
I'm thinking about replacing R7 (8k2) with a 20k trimpot to see if I can dial it down to 4.5-5v range.

Think this would help?

Here's a clip with the new trannies in.

(Playing is still sloppy....sorry)

https://soundcloud.com/michael-wong-482310884%2Fmkii-20-1
 
MichaelW said:
Your a freaking genius, I don't care what anyone says about your socks....:)

Ok, so I took out the old Q3 (184 hfe) and moved what was in Q2 into the Q3 (106 Hfe)
Then replaced what was in Q1 and Q2 with a couple of lower gain MP16A's (38 & 44 respectively).
It has definitely reduced the gating.

Here's a weird thing that maybe you can 'splain me. The pedal seems very sensitive to input gain.
The gating issue is much more prominent with a humbucker (which I used in all the clips). But this is greatly mitigated by putting a buffered bypass pedal in front of it. (E.g., my Klon).
I can't run a boost in front of it or the gating gets worse. Why is this?

As for next steps, I think Q3 voltage is still too high (it's at 7.71)
I'm thinking about replacing R7 (8k2) with a 20k trimpot to see if I can dial it down to 4.5-5v range.

Think this would help?

Here's a clip with the new trannies in.

(Playing is still sloppy....sorry)

https://soundcloud.com/michael-wong-482310884%2Fmkii-20-1
Click to expand...

I wouldn’t go down to the 4.5 vDC range. That’s just not accurate for this circuit.

Do you have another transistor on the 100 hFE range? Put your original Q1 back and then swap around your original Q2 and a new Q3 around 100 hFE.

For my tastes, I like the following:

Q1 at 70-80 hFE, Q1c = 7.80-8.10 vDC
Q2 at 100-110 hFE, Q2c = 150-250 mvDC
Q3 at 100-110 hFE, Q3c = 7.60-8.10 vDC

Obviously Q1 needs some leakage to forward bias.

You are correct on the input. There is so much gain here, that knocking it down a bit helps with Humbuckers.

You can use either a pre-gain pot around 100-250kB or switch in a fixed voltage divider on the input to knock the signal down.
 
Big Monk said:
I wouldn’t go down to the 4.5 vDC range. That’s just not accurate for this circuit.

Do you have another transistor on the 100 hFE range? Put your original Q1 back and then swap around your original Q2 and a new Q3 around 100 hFE.

For my tastes, I like the following:

Q1 at 70-80 hFE, Q1c = 7.80-8.10 vDC
Q2 at 100-110 hFE, Q2c = 150-250 mvDC
Q3 at 100-110 hFE, Q3c = 7.60-8.10 vDC

Obviously Q1 needs some leakage to forward bias.

You are correct on the input. There is so much gain here, that knocking it down a bit helps with Humbuckers.

You can use either a pre-gain pot around 100-250kB or switch in a fixed voltage divider on the input to knock the signal down.
Click to expand...
So much for my "Hand picked from my personal collection perfect for a Tone Bender" transistor set hah!

I don't think I have another PNP with ~100. I may need to bulk up my Ge transistor stock.

I'll futz around with installing a trimmer and report back. I'm actually liking how it sounds a lot better now.
There's definitely more of the treble that I was expecting from this circuit but there's a very cool vocal quality to it for single lines like in my last clip.

Thank you!
 
MichaelW said:
So much for my "Hand picked from my personal collection perfect for a Tone Bender" transistor set hah!

I don't think I have another PNP with ~100. I may need to bulk up my Ge transistor stock.

I'll futz around with installing a trimmer and report back. I'm actually liking how it sounds a lot better now.
There's definitely more of the treble that I was expecting from this circuit but there's a very cool vocal quality to it for single lines like in my last clip.

Thank you!
Click to expand...

If I have any PNP in that range, I’d gladly send it to you. Let me check my binder.

EDIT - @MichaelW Shoot me your address. I have an old RCA 2N404 that @fig gifted me. I have no use for it because it’s the only PNP I have but it’s around 128 hFE with low leakage (40 microamps).

I’m sure Tim won’t mind it being out to good use!
 
Last edited:
Update:

Ok I think I got it!

I took out R7 (8k2) and installed a 20k trimpot then biased it by ear until it sounded good.

Sounds pretty great right now! Plenty of volume and the gating is completely gone.
It's still a pretty "trebly" fuzz compared to my other fuzzes but as I understand this is to be expected.
It's not the prettiest thing in the world and it's also not a "traditional" MkII setup but it SOUNDS GOOD WOOT!

My voltages after biasing:

Q1= 8.09
Q2 = 267mv
Q3 = 8.4

Not hugely off from what @Big Monk recommended to target.

Thank you for the help @Big Monk!

IMG_3054.JPG
 
Awesome ending! Will there be a sequel? I was all into like the downer of the whole bummer sound deal, when the hero says…no WAY dude…that can’t fly cuz I’m gonna take a load off your fanny and hep you fix dit. and then he did! Bravo!
 
fig said:
Awesome ending! Will there be a sequel? I was all into like the downer of the whole bummer sound deal, when the hero says…no WAY dude…that can’t fly cuz I’m gonna take a load off your fanny and hep you fix dit. and then he did! Bravo!
Click to expand...
You guys are all my hero's!

I knew someone would step up and say:

"Oh you just need to try adjusting the flux capacitors and calibrate the dilithium crystals with the thingamajabbit." And sure nuff that did it!
 
Next up.. Burns Buzzaround (Gnat).. Fuschia Fuzz..

Of all the fuzz pedals I’ve built, they can all be my favourite depending on guitar and playing style of the day. (Though I have avoided the ones which Chuck has poo-pooed). If I was left with just one, I could be content, but the variety is very satisfying.
 
@szukalski I definitely need some guidance for where to go from here. Given that you've heard samples of the ones I've built, what's something "different" that I can build next? I did order a boatload of Russian Ge trannies from Lithuania off eBay. (MP42A and MP26). Hopefully out of these two lots of 50 I can find some usable.
 
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