I'd like to share a couple of MOTM modifications that I found useful. Both are simple and useful.
M120: Socket U3 (74HC08 quad AND) and experiment with using a 74HC86 (quad XOR) instead. The two devices are pin compatible. Just make sure you use a 74HC86. I used a 74HCT86 from Radio Shack and it worked fine. The reason for the change was that I was sometimes bothered by the fact that, for low frequency signals on one of the inputs, the counter would sometimes (1 in 16 chances) come to rest at all 0s and, therefore, completely silence the output. Using an XOR assures this can't happen. The sound is definitely not as complex as with using AND gates but it does have a different character.
M800: Solder a wire from the collector of Q1 to the unused pin of the trigger jack. I tack soldered a wire from R1 on the component side to J2 and tie-wrapped it down. This allows the EG to function as a complete ADSR with only a gate signal and no trigger. It will function as shipped when a trigger plug is inserted. I'm surprised this wasn't designed in. I wonder if it might be better to use a series resistor of about 5K in this wire to protect against transients when inserting and removing a trigger plug.
Does anybody else have any useful mods?
John Speth
Object Engineering, Inc
mailto:
johns@...