SOLVED Tone Vendor MKI no sound

allsmoke

Active member
Hi all,

Just finished building the Tone Vendor MKI. Getting sound in bypass, but nothing when engaged. I have an audio signal tracer, and tracing the circuit, I'm getting sound on input, at C1 and on the base pin on Q1 (using AC128 for all 3 transistors). The sound dies on C2, which is listed for 25u, but I used 22u since I have it on hand (I have 22u and 33u). It seems like I'm getting a very faint signal here. After that, nothing. I reflowed the solder, but still nothing. Does it seem like it might just be a fried cap, or does anyone else have any suggestions from experiences with this build?

Thanks all,
 
MKI can be a bear to get right. It’s either try lots of different transistors, or swap out resistors. Since the MKI requires an especially leaky Q1 (I think), it’s even more challenging…
 
I've been helping out a few builders on Reddit with their fuzz builds lately. They all built straight away without testing the transistors first.

A simple warning in the build docs to test the circuit on a breadboard first would go a long way to avoid issues with these finicky circuits.

Builders should absolutely do their due diligence beforehand but all it takes is a single notice next to the component list.

Just throwing this idea out there.
 
I tested all 3 transistors. All are reading 62-63 hfe. I did not breadboard as I was building onto the PedalPCB PCB. I generally only breadboard if I'm building onto a stripboard.
 
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I tested all 3 transistors. All are reading 62-63 hfe. I did not breadboard as I was building onto the PedalPCB PCB. I generally only breadboard if I'm building onto a stripboard.

Recommendations for hFE in this circuit vary but usually it's around 60-70 for Q1 and >100 for Q2 and Q3.
What is the leakage? Leakage is required for Q1 and Q3.

There are long threads about the TB Mk1 on Diystompboxes and Freestompoboxes.org where you can find voltages from vintage units as well as new builds that sound right.
More than anything, getting the right voltages is paramount in vintage fuzz circuits and it trumps any hFE/leakage consideration, though sticking to the recommended values will allow you to keep the circuit stock without having to tweak resistors too much.

The Mk1 is a wild beast and every original one sounds different. The general idea is that it should sound a bit raggedy and unstable and the Attack pot should go from smoother to sputtier, gated tones. Rolling back the volume on your guitar should also result in farty gated sounds.

Here are 3 originals including a super early one in the wooden enclosure that came from Gary Hurst himself (guy in the video talks a lot)


This is the System Mk1 at Macari's, arguably the finest sounding vintage unit and my personal reference (at 10:54):


And this is a faithful reproduction by D*A*M commissioned by Macari's a few years back. Check out the rough decay at various settings

 
Recommendations for hFE in this circuit vary but usually it's around 60-70 for Q1 and >100 for Q2 and Q3.
What is the leakage? Leakage is required for Q1 and Q3.

There are long threads about the TB Mk1 on Diystompboxes and Freestompoboxes.org where you can find voltages from vintage units as well as new builds that sound right.
More than anything, getting the right voltages is paramount in vintage fuzz circuits and it trumps any hFE/leakage consideration, though sticking to the recommended values will allow you to keep the circuit stock without having to tweak resistors too much.

The Mk1 is a wild beast and every original one sounds different. The general idea is that it should sound a bit raggedy and unstable and the Attack pot should go from smoother to sputtier, gated tones. Rolling back the volume on your guitar should also result in farty gated sounds.

Here are 3 originals including a super early one in the wooden enclosure that came from Gary Hurst himself (guy in the video talks a lot)


This is the System Mk1 at Macari's, arguably the finest sounding vintage unit and my personal reference (at 10:54):


And this is a faithful reproduction by D*A*M commissioned by Macari's a few years back. Check out the rough decay at various settings


Given the amount of leakage required by the circuit, the gain of each transistor would be a fair amount less in circuit, no? Of course, those numbers DO work best. But without the required leakage those numbers mean almost nothing. I highly doubt Gary Hurst was sitting there measuring HFE, anyway. Ge was cheap. Why measure when you can just grab another one from the box? I think they put three in and, as long as it worked, that was that…
 
Given the amount of leakage required by the circuit, the gain of each transistor would be a fair amount less in circuit, no? Of course, those numbers DO work best. But without the required leakage those numbers mean almost nothing. I highly doubt Gary Hurst was sitting there measuring HFE, anyway. Ge was cheap. Why measure when you can just grab another one from the box? I think they put three in and, as long as it worked, that was that…
You make great points for sure but I've had this fuzz on a breadboard for weeks and random transistors don't work well for me.
There are a number of issues every time like the effect fading in when switched on, the Attack knob cutting out at the end of the sweep, noise etc.

I have 70 Germanium transistors now, there's no way I'm gonna pop them in randomly until it works. I'm gonna try and use a method to the madness first so I can reproduce it in the future.
 
You make great points for sure but I've had this fuzz on a breadboard for weeks and random transistors don't work well for me.
There are a number of issues every time like the effect fading in when switched on, the Attack knob cutting out at the end of the sweep, noise etc.

I have 70 Germanium transistors now, there's no way I'm gonna pop them in randomly until it works. I'm gonna try and use a method to the madness first so I can reproduce it in the future.

Sort before, after or during, you’re gonna sort regardless. There’s a reason Gary Hurst switched in the Vox DB circuit early on…
 
I didn't include leakage numbers in my post because I didn't have them at hand.

I have no problem with sorting. I've measured all my transistors so I know which ones are likely to work. If they don't then I can start trying out other ones but each time I know the values so I can learn about what works.

There is no better system, this is just what I'm doing now based on info I found. For Fuzz Faces and Fuzzrites, forums have been useful so I imagine they are for Tone Benders as well. Ready to change my approach if it fails.
 
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