[sdiy] TR 606 trigger i/o modification help and notes

[Anthony Bisset]

I could use a bit of help confirming I have chosen the appropriate points
to extract/mix trigger pulses. I am experiencing some cross triggering.
Whenever I externally trigger the hi-hats low or hi-tom are also
triggering.

In order to add trigger in/out functionality to the 606 I added:

     OUTPUTS (center pin)   INPUTS  (TRIG -> DIODE -> DIODE BELOW)

BD   Q15		    DIODE from R63 -> Q15 (center pin)
SN   Q18		    DIODE from R98 -> Q18 (center pin)
HT   Q302		    DIODE from R311 -> Q302 (center pin)
LT   Q304		    DIODE from R313 -> Q304 (center pin)
CY   Q29	            DIODE from R141 -> Q29 (center pin)
OH   Q27		    DIODE from R138 -> Q27 (center pin)
CH   Q22		    DIODE from R133 -> Q22 (center pin)

Robin Whittle  suggested I boost the 15v trigger signal by .6 volts (since
we lose that much with our trigger mixing diodes)...  Is this simply a
matter of changing some resisters around the 15v supply IC or do I need
to operate locally at each trigger point?

As promised I'll forward a well documented list of 606 mods (some new,
some improved) to sdiy, confusedmachines, AH, etc when I'm done.

The discussion on vactrols led me to utilize one on the snare section to
prevent crackles when changing the decay (something about the transition
lag prevents the circuit from crackling).

Also, P9's old stuff about the schmitt trigger IC led me to install pots
in place of the resisters that tune the 6 oscillators.  The result is very
cool PWM/ringmodish clangs and bells with the cymbal and hats.

Next I'm working on a New 606 BassDrum composed of BBD as feedback
oscillator with clock rate being swept down to drop pitch. Grimey.
I used to make kick drums with a ue405 in feedback loop config with ms20
filter regulating frequency.  909/808/xbase kicks sound boring now.

I can basically  replicate it on my WAD with VCFS but the WAD doesn't
have enough clock bleed through (yeah, not enough!!!).  The UE 405
compression circuit was probably helping too.

-Anthony