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That looks really nice ! I haven't tried etching yet, maybe once I move out of my current (too small) place !

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Haha no worries :-)

I'm starting to think it might actually be working as designed and the differences in response of the SENS pot might just be due to components tolerance...

I am no expert in transistor based circuits but I've swapped the 2N3392's on the breadboard using lowest HFE for Q1 for example and playing around with Q4 and it do get some subtle but noticeable difference in the overall effect of the SENS pot. I went ahead and swapped Q1 on the pedal with the lowest HFE I could find (167) in the pile and will just give it as is to the boy, I think it sounds mostly as it should.

I have ordered from small bear some of those nicer "smooth" 3392's that Brian has in the photo, I'll play with them when they arrive (takes a couple of weeks to Australia).



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So I tried to dig a bit more, tbh, that's hitting the limits of my electronics capabilities :-)

Basically, the lack of useful "range" on SENS starts as soon as Q4. At its collector we get positive "mounts" (sorry I didn't take a photo, large round mounts and very narrow valleys) whose width varies a little bit with SENS but that's about it (except at the very beginning of the pot. At zero there's nothing, turn a mm or so to start getting something, but as early as 8 O'clock you get those mounts and the barely change for the rest of the pot.

Just in case something's wrong with my build, I've breadboarded the circuit (well... the BRASS path) from input to Q6 (I skipped Q2/Q3 "clean path" and I've stopped for now at Q6, so no tone stack).

I observe pretty much exactly the same thing. I've taken photos of the scope at Q6 emitter with various positions of the SENS pot. Input is +/-150mV (300mVpp) 500Hz.

SENS at 9 o'clock:


SENS at 12 o'clock:


SENS at Max:


I think I'll leave it there :-) Mostly I wonder if that's expected.. I watched a couple of demos of Brassmasters and mostly the sound is "similar" but on all of those demos, there is a tonal change with the SENSE pot, if subtle, while for me, there's maybe a bit of a volume change in the first half but that seems to be about it.

Or could it be that my 2N3392's are not quite right ? They are brand new from Digikey and measure with my little GMA328A around 188 HFE from Central Semi (https://www.digikey.com.au/en/products/detail/central-semiconductor-corp/2N3392-PBFREE/4806860).

I'll interject since it has been part of the discussion in the thread.

Obviously, the forum has taken a major downturn and that is 100% my fault. It's clear I'm not putting in the work on mbp right now. I've reached a stage of burnout that I just can't seem to recover from. Sixteen years of working solo on a singular "project" has taken a toll and I don't know how to get back on the right side of things. An extended sabbatical would probably be the right thing but I think that would end up pushing mbp further into irrelevancy (in terms of my colleagues and "competitors").

So, I've just been plodding along hoping the stars will align again.

Sorry to hear that ! I'm a newcomer and really love what you do and the quality of it, for what it's worth !

Take care of yourself, it's the most important in the end.

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Found a bit of time to spend with the scope, still trying to ascertain wether it's behaving as it should or  if I need to dive deeper :-)

Those measurements are made with a 500Hz sine wave in the input, at around 500mVpp (+/- 250mV) it's hot but not necessarily that far from what my son's Stingray will push out, I can try something smaller this week-end). BRASS switch on 1 (mid focus), SENS on max.

* With clean only (brass down to 0), there is a slight distortion. A bit "tube'ey" in fact: the positive half wave is a bit flattened and the negative one a bit pointy (yellow is input, blue is output)



* With brass only (clean down to 0), HARM in position 1 (left), so it should be according to the description "some extra octave in parallel with the EQ", I get this:



FFT:


So you see I get pretty much every integer harmonic under the sun, I don't see any particular "octave" emphasis but maybe that's how it should be.

* With the switch in the "right" position (feeding the full octave to the EQ):



FFT:


Which shows similar harmonics but with descending intensity.

Additional detail, I meantioned earlier, SENS doesn't do much except at the very very beginning of the pot. The first few degrees of turn there is NO signal at all in the "distorted" path. Then it quickly comes up, there is a very small region until around 9 o'clock of variability, and from there it doesn't do a whole lot for the rest of the range. You can see almost no change to the wave on the scope for the bulk of the range of the pot past 9.

On the week-end I'll try to understand a bit of the circuit and poke around with the scope and the audio probe to see if any "path" is obviously bad but I'm not a proper electronician :-) So any hint welcome !

[Edit] Looks like 500mVpp is just way too hot for this circuit. Bringing this down to 200 and the SENS pot has more usable range. Still curious about what you guys think of the rest.

Actually for those of you who have one... I suspect something might not be quite right with mine. I'll scope around etc... this weekend but basically when switching HARM from left (octave mix) to right (full octave) what we hear is kind of the same square-wavy fuzz, just less loud.

Is that expected ? I wonder if the octaver is working.

I'll compare with online demos etc...

[Edit] testing with clean bass pot all the way down. Also nothing comes out of brass of sense is 0 which might be normal, but very very little difference from sense at 9'o clock all the way up.

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Love that artwork!

I wish it was "art" :-) I couldn't draw a thing if my life depended on it ... So that's the output of some AI on the internet that I coerced into doing something not too far from what I wanted :-)

Frankly this is the most use I ever had for AI :-) We get quite the pressure in my day job to adapt to AI or be replaced (SW engineer) but so far, apart from being a glorified google summarising the worse answers from StackOverflow, I found AI to be mostly a waste of time, at least when tackling anything moderately complicated.

The other great tool is vectorizer.ai ! It takes the PNG output from Gemini or chatgpt and produces excellent quality vector graphics that I can then import into Inkscape (I then use Scribus to generate the final layered pdf with the right spot colors for Tayda. No commercial software involved, all in Linux :-)


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I've found breadboarding to be a good corrective for hoarding. There are many circuits that seem exciting...until I breadboard them and get to play with them a little.

On that note I am a real fan of PPCB ProtoBoard, having the screw terminals for the pots makes a huge difference compared to all the other options

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Thanks folks ! Found the libraries. That will keep me busy once I'm done through my current backlog

From the Album "Solder and Rust"... Ok that was a bad ozzie joke :-) I'm on a roll this week, here's my Beanscream :-) I went for BJT input buffer because I'm short on JFETs, and I'm happy to get an idea of what the OG sounds like but I can always 'upgrade' later :-)

Cheers !


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I still use the old library and Dave at effects layouts has a library I also use. He has a tutorial here: https://www.youtube.com/watch?v=X67wazQz0zQ I can't remember if he links it in the notes or where I got it. It's a great multi video tutorial though.


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Thanks ! I'll have a look.



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Wait until you learn how to make a schematic and layouts. Then you're hoarding on colossal scale.

Hah !

I started playing a bit with Kicad :-) I might try some simple things next holiday, we'll see...

Talking of which, I found somewhere a converted (to Kicad) old version of @madbean 's library (V3 I think). Are you guys aware of something newer/better put there ? I remember seeing a post by Mr Bean mentioning he was working on a newer release but I doesn't seem to have eventuated. I would even happily pay for it :-)



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It's just me or is PCB hoarding a thing ? :-)

I keep buying "that looks like this might sound good" from Brian (or Aion, occasionally elsewhere)... And end up actually building only a fraction of those.

Sometimes I pick up an old one and bam ! It's been updated ... Then the temptation to buy the updated version....

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Very very cool. If you haven't built one yet, build a green Russian muffin. As a bassist, it's my go to fuzz.

I built one ages ago from a fuzz dog or musikding kit, I don't remember :-) before I knew what I was doing for sure :-) I might pop it open one of these days to look at the damage, he doesn't use much.

I'm going to do a violet ram's head soon too for guitars. I have the Tayda box already and I've breadboarded it to play with different diodes:



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Make sure to give your son the blurb from the build doc about how the knobs interact.

Thanks, good call !

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