Early 2 Knob Death by Audio Soundwave Breakdown

[anders]

There is a schematic in THIS thread of a very early version of DBA Soundwave Breakdown.

Whipped up a quick vero because this simple circuit looks quite primitive and odd.

[Hozy31]

Which row is ground?

[anders]

Oops, thanks for that. Layout is updated.

[SonusFluxa]

Just built this. Not sure if verified...definitely getting heavy square wave fuzz, minimal sustain, and not quite sure exactly what the knobs are doing yet. Sounds killer either way.

[anders]

Awesome! The square knob seems to  work like primitive filter and the Sine knob sets the bias of Q2. Which transistor did you use?

BTW, your description of it sound identical to the tracer over at FSB so I guess it's verified?

[SonusFluxa]

MPSA13. I also subbed the two 4M3 resistors with 4M7, and the 1K5 with 2K since I didn't have those values on hand. I flipped the transistors, but the sine pot didn't like that and started smoking, so I'm going to replace that when I get home from work and see if that changes the sound at all.

[SonusFluxa]

I changed the pot, sound was about the same. I switched the places of the two transistors and that made a slight difference (might have damaged one in the previously mentioned smoke incident), but overall still the same. I chuckled while reading his description. I would say it's verified.

[squirrels]

How does this one sound compared to the later version? I have an extra 1590A sitting around waiting to be used.

[SonusFluxa]

The 3 knob seems to have more sustain, from what I gather from demo vids. Mine also doesn't oscillate. I can record a quick demo tomorrow if you'd like.

[squirrels]

Yeah sure, it's always nice to hear what people have built. I'm looking for a crazy fuzz to compliment my Harmonic Transformer and Fuzz Factory clones. I may not go with this one yet, I'm missing a 50k pot. All I really have right now is a 25k but I guess I could use that for the time being.

[SonusFluxa]

Looks like I lied about the lack of sustain and oscillation.

Guess I hadn't messed with the knobs enough. There's a sweet spot toward full clockwise on the sine knob where you get noise, as well as noisy sustain. Full cw, no volume. Ccw, less sustain. The square control is a bit more subtle ( as in I can't tell the difference between full cw or ccw).

[squirrels]

Sounds pretty good. I may have to give it a shot.

[squirrels]

I was looking at the layout on the main site, maybe the square wave pot would work better with a 250k?

[heuermh]

Ah smoke.

This one has got me twice already, first Q2 started smoking, then later after reflowing a few things the B50k pot started on fire.

I'm left with something 1000x louder than the input signal with a ton of self-oscillation.  I'm using MPSA13s and also tried MPSA12s.  When you say "I flipped the transistors" do you mean swapped Q1 and Q2 or installed them backwards or upside down (so the transistor pinout doesn't match)?

[SonusFluxa]

I meant flipping the pin out. DBA really knowns how to make a testy circuit.

[heuermh]

Thanks.  Sorry if I'm being thick.  :)

Does it work better (not start fires) the wrong way

 vero       MPSA13
             ----
  E  <---   / C |
  B  <---  |  B |
  C  <---   \ E |
             ----

or the right way?

 vero       MPSA13
            ----
  E  <---   | E \
  B  <---   | B  |
  C  <---   | C /
            ----

[heuermh]

Ah wait!  By tracing the schematic I found another problem with my build, C3 is in the wrong place.

I still could use confirmation on the transistors; I assume they should match the schematic.

[heuermh]

Shit!  That didn't do it, smoked another Q2.  This one's going in the bin.

[SonusFluxa]

Sorry to hear you're having so much trouble! Just to be sure, I have the transistors oriented as per the layout.