Tone Vendor MKI Attack pot not much effect.

Matopotato

Matopotato

Active member
Hi,
I just managed to finish MKI and there is a lot of fuzz in it. I modded it by setting a trimpot (20k) for R7. Lowering it gives a sort of dying battery sputter, and 75%+ makes it less fuzzy almost like a boost.
First question/issue is that it has a high noise floor (?), but I was sort of expecting that with fuzzes. But reading other posts it seems to be possible to adjust.
The second issue is that the Attack knob does not do very much. When off or almost off it kills/turns effect off like close to 0 on volume knob. (Which is good and expected) But above 15% it does not do much all the way tTo the top.
I checked the thread by @Coda (MKII issue) but the fix there seems not to be my case at a first glance. Also checked the thread on MKII by @TSReppe .
The transistors from Das Musikding were 1 OC75 and AC125F and AC125U. I tried to compare the hfe on the AC125s but they were very close as I remember.
No idea how to check for leakage and if that would have effect. Musikding are good at sending matched and appropriate transistors imho.
Thanks in advance.
PS I like the casing (from Tayda, long transport...) and knobs combination, will try some decal printing later on.
 

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I have studied as much as I can to figure out how to measure Ge transistors. Most helpful I found R.G. Keens explanation of Fuzz Faces and how to measure as well as DIY Guitar Pedals Youtube clip (
).
Just for fun I put one Ge transistor in the freezer for a little bit and its values changed considerably.
So next step was to put the ToneVendor MKI in there as well. Some 10-30 minutes later and now it gates a lot more. The attack below noon, more or less shuts off the effect. So it had quite a dramatic effect. On the other hand, I wanted to reduce the gating and get more Fuzz...
 
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I decided to try out the advice from @danfrank :
danfrank said:
Hi everyone. I ordered a Tone Vendor MK1 board a bit ago. I've made most of the fuzz box types in the past except for this one. I was happy to see that PedalPCB offered a board for the MK1. I've read most everything I could find on the internet about the MK1 and the data and opinions about the MK1 are all over the place. So, what is good data that works for building the MK1 and what is hogwash??? Lol!
Well, I built mine and here's a few observations that I've made... Hopefully this will help other builders:

I found that Q1 works best if it has a gain of around 55-70, it also needs to be "leaky", like around 200ua. This is because the leakage is what biases Q1. A higher leakage might work better but the higher the leakage in a transistor, generally the higher the noise. Transistor noise is critical with Q1, noisy Q1 = noisy circuit.

I found that a low leakage transistor works well for Q2, and what worked for me was one with a gain of around 100-110. I still need to try lower and higher gains for Q2 to see what that does to the circuit.

Q3 also needs to be leaky, I found a leakage of about 100-150ua works ok. I like a lowish gain also, like around 80-100. The higher gain Q3 is, the less range the attack knob has. In other words, the higher the gain of Q3, the less "gating" range is available. As for Q3 leakage, it needs to have some but not too much. The more leakage Q3 has, the lower the voltage will be on the collector of Q3. Most everyone says a Q3c voltage of 8-8.5 is desirable, which makes sense because if Q3c voltage is lower, like in the 7s, Q3 won't gate much, which I found to be true.

Also, a log or audio taper pot would probably be more versital for the attack control, more gating range on the attack knob.
This circuit still needs a lot of time spent to get the correct combination of things so it sounds good. I'd have to say that transistor gain, leakage AND noise are the big three factors determining how the MK1 will sound. A lot of the variance in opinions across the internet may be because of individual taste in sounds, but this is pedal building, so who knows...
Lol!
Click to expand...

I managed to get hold of:
Q1: ACY30 hfe 82 leak 210uA
Q2: SFT229 116 and 40uA
Q3: 2N321 82 and 110uA
And it just became a different pedal. Hiss don't bother me at this point so I did not check that out.
The attack knob went from 3/4 useful to about 1/2 + some usefulness.
That was with single coil
Then I tried humbuckers and it got in to some kind of "over fuzz" territory when pedal and volume was close to dimed. Like gating but more of an overall subdued sound. really cool, but (for me) unexpected.
So I have the "original" ones which gated most of the time. Not a bad thing, made it very "fuzzy" and felt vintage.
With the new set it lost a touch of the fuzz and is almost looking over its shoulder towards distortion pedals :)
But with that overfuzz mode. Still it is fuzzy but quite cleaner especially with Single Coil.
So some part in my ever GASing brain begins "I want both". And after some control ego saying "It's not gonna happen, you can't solder that" I began to contemplate "what if".
I do have the board socketed, so I can insert wires to anywhere. I could drill some more holes for switches like Q1 Q2 Q3 and flip between each transistor on an individual basis to make it "as complex as you can make one of the simplest pedal designs".
Or one switch for each triple. (Will experiment some to see if it would be useful. Just 9 or so iterations).
Anyway, my question now becomes: How would one go about to set this up?
I am just assuming with some wire and a switch, you ought to be able to direct which transistor to engage.
Is it just to connect emitters and bases to their respective spots on the socket an set the switch to select collector (or some other combo). Now, they are leaking so I assume one have to think this through.
Or is there somewhere a pcb for "Those crazy guys out there who want to transform an MKI into some kind of Fuzz monster"?
Any help or honest "don't go down that road pal" help is appreciated. @danfrank or @Big Monk ?
Many thanks in advance either way.
And again, a huge thanks for all who contributed to this thread! I really do appreciate it.
 
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Big Monk said:
Just to be clear: You want to use 3 transistor pairs for each position on a switch?

The easiest way, if you had the space, would be to put each pair on a 3PDT toggle.

I can't say how switching each device will affect bias voltage, etc. but that's how I would do it.
Click to expand...
Yes, either 3 pairs and one 3PDT or 3x "single" switches that would allow for more (ridiculous and excessive) control, individually.
3PDTs might be challenging to fit but good point.
If instead I would try to join 2 out of 3 legs and use a 1 switch for the last leg, is that even possible? (Or 3PDT for all 3 flips in one go) And if so which ones can be joined and which should be put to the switch?

I have added a bias trimpot on Q3 and in the second setup of transistors it had little impact so I think/hope biasing is of less impact.
 
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A 3PDT flip (not stomp) with on-on 2 way per each "opposing" transistor pair is what you proposed, right? (I thought stomp) wite centerpieces to the socket and one transistors on each row.
Will it pop a lot when switching?
 
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Big Monk said:
Yes.

Q1 might pop because it's couple directly to the power rail but I don't think Q2 and Q3 would.

Maybe it would be best to determine which transistor swaps give you the most benefit and just switch those.
Click to expand...
Thanks!
Yes, I can get all the stuff, and socket on the 3pdt so I avoid soldering the transistors. Then I can fliptest and determine if one setup is optimal or if flips are useful. After that, drill and solder accordingly.
I really appreciate the help.
 
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I managed to fit 3x 3pdt on-on switches and arranged the original transistors with the new set. And it works!
There is no pop sound when switching Q1, so I am guessing the circuit/board already handle that.
I felt I got many more options out if it now. The Attack knob gets a bigger range in some combinations. The volume on the guitar has higher impact than expected, which is good. Not as dramatic as fuzzface, but more "useful" imho. With humbuckers volume over ~8 it sort of "overgates". A cool sound, but very "soft".
The bias pot got more sensitive and I am glad to have added have it.
The pedal has some hiss and lots of untamed sounds, but I take that as its charm.
Only "negative" is a squealing, whining, sort of high-pitched noise in some settings from Q2 SFT229. Not sure if 80-100pF on base collector would help that, but plan to try it, @Big Monk ?
Again, many thanks for help, tips and support throughout this build!

UPDATE: Tried some 80, 100 and 220 pF and hiss changed, but not the squealing thing. It comes with the Attack know at say 2 or 3 o'clock. but lowering the Level removes it and then I can bring back level and it is not audible. But the Attack knob is now sort of just waiting for a touch to go back to the squealing sound. Playing somewhat loud seems to remove it as well, but hard to tell if it gets lost or just drenched.
 
Last edited:
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Just for the archeologists: I had used quite long cables because I wanted the 3PDTs to be Q1 Q2 Q3 order when playing. I gave up that and connected each 3PDT to its closest socket, and the whine and squeal was gone.
I also noticed that some transistors legs were thin enough to cause glitches in the 3PTDs, so skipped them and soldered the transistors on to the 3PDTs, with wire only to the sockets on the pcb. Less chance to change them around, but by now I am happy with the ones I got in there. In the end the range of the Attack got quite a bit better as well.
 
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Matopotato said:
Hi,
I just managed to finish MKI and there is a lot of fuzz in it. I modded it by setting a trimpot (20k) for R7. Lowering it gives a sort of dying battery sputter, and 75%+ makes it less fuzzy almost like a boost.
First question/issue is that it has a high noise floor (?), but I was sort of expecting that with fuzzes. But reading other posts it seems to be possible to adjust.
The second issue is that the Attack knob does not do very much. When off or almost off it kills/turns effect off like close to 0 on volume knob. (Which is good and expected) But above 15% it does not do much all the way tTo the top.
I checked the thread by @Coda (MKII issue) but the fix there seems not to be my case at a first glance. Also checked the thread on MKII by @TSReppe .
The transistors from Das Musikding were 1 OC75 and AC125F and AC125U. I tried to compare the hfe on the AC125s but they were very close as I remember.
No idea how to check for leakage and if that would have effect. Musikding are good at sending matched and appropriate transistors imho.
Thanks in advance.
PS I like the casing (from Tayda, long transport...) and knobs combination, will try some decal printing later on.
Click to expand...
Finish looks great. What hammered paint did you use?
 
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