MOTM-120 Mod suggestion

[Paul Schreiber]

1) The HCT means the inputs are TTL switching levels (0.8V and 2.4V). A HC is
CMOS levels. Either will work. HCT is actually getting harder and harder to find.

2) This brings up an interesting point: what differences would ANY gate make in this circuit?
(The MOTM-120 has 2 4-bit counters that are AND'ed together in CROSS mode)

If we think in terms of "pulse density" of the output, AND we recall that a 25% duty cycle
pulse sounds like a 75% one, here is a chart:


HC00 NAND = 75% high, 25% low
HC02 NOR = 75% low, 25% high
HC08 AND = 75% low, 25% high
HC32 OR = 75% high, 25% low
HC86 XOR = 50% high, 50% low

I originally thought about a PAL that you could select different gating, 
but due to cost left it out. Maybe for a MOTM-125 Super Mux??!?

The AND is in there because it is the "correct" digital version of a VCA
(only have an output when the 'CV' input AND the data are both true)
but certainly an XOR will be less "reedy" sounding.

This is the fun of DIY, and why I give full schematics & theory with the modules
(no potted boxes here!)

Paul Schreiber
Synthesis Technology
www.synthtech.com