Tone Vendor Mk1

yazooligan

yazooligan

Well-known member
Build Rating
5.00 star(s)
Full report on the sound (and maybe a video demo) coming shortly.

EDIT 15/5/24: Last year I caved and got a matched set of transistors specifically for a Mk1. After another year of working on other projects, I came back to this one and finally put the transistors in and...WOW. There it is. Instantly reminded of why I fell in love with the Mk1 sound in the first place. So worth it.
 

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Last edited:
Dan0h said:
Im curious about the blue tape inside the enclosure? Made me think about how Reeves paints all the insides on his builds. Just wondering.
Those Russian ufos look cool on this build.
Click to expand...
That’s just some masking tape I lined my testing box with to avoid shorts while I mess with stuff.
 
I couldn’t find the parts this build actually called for, so I went with some old Russian MP-40A’s and…it doesn’t sound great.

For one thing it’s not very loud. Even with both knobs up full it’s kind of average sounding, and the volume fades in and out just a bit with some regularity, almost like a small gate was modulating the volume.

The sound itself is distorted and fuzzy, just not the way I’d expect a mk1 to sound.
 
The MK I is very sensitive to the the transistors used, and especially the leakage. I think it's actually leakage biased in fact, so if you haven't accounted for that, it could be the source of your problems.
 
Yeah, the early fuzz stuff is reliant on leakage to bias correctly. If you haven't got a range of transistors to choose from, then a matched set may be the best bet. I had a lot of pain getting a good pair from a decent selection.
 
yazooligan said:
I couldn’t find the parts this build actually called for, so I went with some old Russian MP-40A’s and…it doesn’t sound great.

For one thing it’s not very loud. Even with both knobs up full it’s kind of average sounding, and the volume fades in and out just a bit with some regularity, almost like a small gate was modulating the volume.

The sound itself is distorted and fuzzy, just not the way I’d expect a mk1 to sound.
Click to expand...
I posted a build report recently with detailed info on transistors, voltages and tweaks. Give it a read, maybe it'll help you. I got a lot of info from long threads on other forums. My MK1 sounds great and very close to the demos I've heard.

Tone Bender MK I - Vintage Edition

Hello everybody. I'm very happy to present my most rewarding build to date: a Tone Bender MK I. I built it on turret board with 1W carbon film resistors (but there's a 1k8 1/4W metal film resistor in there too) and big axial capacitors. The coolest thing about it, however, is the vintage style...
forum.pedalpcb.com forum.pedalpcb.com
 
andare said:
I posted a build report recently with detailed info on transistors, voltages and tweaks. Give it a read, maybe it'll help you. I got a lot of info from long threads on other forums. My MK1 sounds great and very close to the demos I've heard.

Tone Bender MK I - Vintage Edition

Hello everybody. I'm very happy to present my most rewarding build to date: a Tone Bender MK I. I built it on turret board with 1W carbon film resistors (but there's a 1k8 1/4W metal film resistor in there too) and big axial capacitors. The coolest thing about it, however, is the vintage style...
forum.pedalpcb.com forum.pedalpcb.com
Click to expand...
Copy that. To clarify, I got the MP-40A’s in three bags of matched hfe, but I got the same result even when using three of the same hfe. Is that how leakage is measured?
 
yazooligan said:
Copy that. To clarify, I got the MP-40A’s in three bags of matched hfe, but I got the same result even when using three of the same hfe. Is that how leakage is measured?
Click to expand...
I measure leakage with a cheap tester called TC1. It's the Iceo parameter.

The problem with buying matched sets is that different vendors have different ideas of what is right for a circuit. The MK1 is a finicky circuit. Theoretically you want decent leakage for Q1 and Q3 and also enough gain. The voltages are where it's at IME.
Ideally try to build it with stock resistors before you start messing too much with the biasing.
 
Last year I caved and got a matched set of transistors specifically for a Mk1. After another year of working on other projects, I came back to this one and finally put the transistors in and...WOW. There it is. Instantly reminded of why I fell in love with the Mk1 sound in the first place. So worth it. I'll update the OP with pics!
 
It seems MP40s are the way to go for the MKI. What hFE and leakage did you use?

IIRC Q1 needs hFE 60 and leakage >150, Q2 needs hFE >100 and no leakage necessary, Q3 hFE >100 and leakage >150
 
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