Boom Boom Badaboom !

[benh]

Tayda delivered, I found some time, here's the next toy for my bassist son !

Only quickly tested on a guitar which I can't really play, it sounds glitchy and all over the place but I think that's the spirit :-) Definitely not meant to play a guitar chord through that thing !



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[jimilee]

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


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[NorthCoast]

Very nice. Very shiny.

[jwin615]

Very nice. Classic call back to the og art. I love the brassmaster circuit.
Make sure to give your son the blurb from the build doc about how the knobs interact.

[benh]

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

Thanks, good call !

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[benh]

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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[jimilee]

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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Very cool.


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[benh]

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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[benh]

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.

[benh]

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).

[NorthCoast]

I don't know the answers to your questions, but I really enjoyed the scope porn!

[benh]

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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