Wednesday, April 6, 2011

Monotron^2 - Troubles

So, my LFO routing was not quite right - added unnecessary diodes in wires and actually prevented signal from leaving LFO section!
VCO 2 does not work - this is the monotron unit that I first modded - so may have damaged something via over heating! (I get 3.5V instead of 4.58V - as with VCO1 from newer unit!)
Other issues: CV (pitch) input voltage gets divided, so can only control one unit at a time from a single CV line - can't just put them in parallel (I don't know why????) else you have to play notes way up the keyboard. So will try to link units via a different connection point!
I am getting a strong gate signal across both units, and it is re-triggering both LFO's perfectly.
The audio out mixer works a charm (nice and clean too - all noise does come from monotrons).
Also, square wave mod works nice, as does the PWM and the noise gate circuits.
Finally, using the second monotron's filter section for a separate filter also works great, but I do have to put an input resistor on it, as it totally distorts right now. The aux in has 10k resistors on each channel, and I found that this distorts with a hot signal, so I'll probably put 15k or 20k instead - mono, of course.
I have not determined if the CV mixer is working yet, but it seemed to with one channel. And I also got the polarization going on the one working VCO, and it does do some sort of voltage inversion - very cool.

Had a short on CV mixer across output and supply - now fixed.

Should have used stranded cable for VCF connection from Monotron++ board, as it keeps breaking while I trouble shoot.

Sound checks in the studio.
Almost there - sounds fat with single VCO...
Get some fat tones with the one VCO and square wave mod, and since the gated output comes from the audio mixer, can get some added resonance from the second filter without any aux input!
Still, it will be even fatter with dual VCO...
Will update very soon with trouble shooting and repairs.

Monotron^2: Coming Together part 2

Without testing - just too excited about getting the thing working!