Archive of the former Yahoo!Groups mailing list: MOTM

Yippee!!!! I played with some resistors tonight and got all 4 of my MOTM-300s soft syncin' across a tuning range of up to 4 octaves. I'll tell you what I found - your mileage may vary, of course. I'd like others to try this - it's 100% safe since I didn't mod the VCOs at all.

Soft sync did not work at all for me before I started - I had the "medium sync" syndrome Paul spoke of where the two independant pitches disappear into 1 pitch.

First I wired a 200k pot between the hot lugs of 2 spare jacks (and gnd to gnd, natch) and plugged patchcords up between the jacks and 2 VCO sync inputs (both switches set to "soft"). Then I varied the pot to add resistance into the sync patch and found a range which allowed soft sync to work. Below this resistance range I got "medium sync", above it there was no sync. I used 2 oscillators tuned 1 octave apart, detuned to 3-5 beats per second. I measured all combos of 2 oscillators synching, took the largest minimum and the smallest maximum resistance. I found that for a 2 oscillator connection, that adding a resistance of between 4.5K ohms and 19.5K ohms works for my 4 VCOs. Take the median and divide that by half to split into 2 resistors (one for each VCO sync input), and you get about 7K ohms added resistance per VCO.

Next I tested soft syncing of multiple VCOs. I took a mult panel that I recently made up, and modded one of the mults to add a 5.1K resistor (cause that's what I had laying around) from each jack's hot lug to a common point (NOT ground). So patching all the 4 VCO sync inputs to this mult adds about 10K per patch. You can play with the resistance values without modifying your module.

All four synced up! I set up a patch with fundamental, octave, octave + fifth, and two octaves + a third. With soft sync what you get is the individual pitches remaining, but because there are no beats, your ear blends it all together into a new timbre.

My VCOs aren't tweaked to track perfectly yet, and I'm running them on different MIDI/CV channels which adds some error. If I play low notes, it sometimes doesn't sync until it phases through a cycle. I'm going to tweak the resistors some more, lowering the value to attempt to get a slightly more aggressive sync.

I'd like some others to try this to see if my experience is typical or not. Let's give Paul some data to work with. What resistances work for you (or does adding resistance NOT work at all)? Please DO NOT mod your VCOs - I don't want somebody to tear up a trace and I DON'T claim that this is the permanent fix.

Enjoy - soft sync is very cool!

Rocket Man