This is another, "I shoulda built this a looooong time ago" pedals, but of course, I'm getting to the party late. As with my Superfuzz, lots of identical transistors screams "transistor array" in my head, so I went the Pickle route. I had to search hi n' lo for "just" the right array, and the MPQ2484 nails things down pretty well. The MPQ2483 sounds pretty good too, but it's a lower gain version, in between a 2N3904, and a 2N5088. The MPQ2484 gives me gains a tad above the 2N5088. In any case, it rips pretty good. Here's the verified vero;
The transistor and cap values are a mix of some Triangle, and Ram's Head values, and then tweaked to suit my ears. Using the collector/emitter resistor value calculation of the first three stages, it gives me a total gain value of 412, which is plenty for me, even without any tubes to push. I used two different values for the clipping caps, 0.05uF in the first section, followed by 0.15uF in the second section. I find that the clip frequencies are just right for me. The feedback sustain, even at bedroom volume level is fantastic. The diodes are unknowns. There's no numbers on them, only 3 color bands (white / violet / red or brown), and the letters "TSC" (Taiwan Semiconductor). I can't find any info on then, and even though they show typical forward voltages of .65 to .7, these just
DO NOT perform like 1N4148's or 1N914's. I don't know what it is about them, but they add a more jagged edge to the sound. Maybe I'm hallucinating, maybe I chowed down on the locoweed, I don't know, but these sound different. I picked them up from a local guy, who got a whole whack of them from Northern Telecom. I'm still looking for data on them.
The voltages are as follows (E / B / C), going from input to output. Power supply = 8.95vdc, and I measure 8.80vdc after R24;
Q1; 39.3mV / 0.636v / 4.06v
Q2; 31.8mV / 0.627v / 4.06v
Q3; 29.7mV / 0.622v / 3.99v
Q4; 0.826v / 1.404v / 5.01v
I don't have the customary video done yet, but here are some teaser pics of the board for now.
I'm so enamoured with the resistor and cap values, that I've been also testing some other transistors as well on the breadboard. The usual suspects, like the 2N5088, and BC550C sound really good too, but I've found some lesser known (to me, anyway) transistors also rip and snort pretty well in here as well. The 2N3390, Russian KT342VM are very good, and one that really plays (and looks) the part as well, is the BCY59X. This one people, has grown on me. It's a metal can, like the BC108/9's, but on steroids. It's like a BC109, and a 2N5088, got together, and begat an evil redheaded child. I'm already planning to build a second one, right after this one, with the BCY59X's, but
maybe slightly different transistor and cap values in the tone section. I like the tone section the way I have it arranged right now, it's got a healthy range, and the sustain is just off the map with what's on my board right now, but who knows what a little more tweaking will reveal.
If you want to build a BMP, but not use the regular, run-of-the-mill transistors, the aforementioned should make your, ahem... pickle crunchy.
I've been playing around with carbon comps, just to get that retro look, but I was short on 100K's, so some carbon films had to fill in. Just the same... Daddy likes.
