MOTM-120 Mod suggestion

[John Speth]

For anybody building the MOTM-120...

A nice mod you can try is to socket the 74HC08 (quad AND gate) and compare
it against a 74HC86 (quad XOR).  These 2 devices are pin compatible and the
socket makes comparison easy.  When in the cross-mod mode, the sound is very
different - so much so you might even want to rig a piggyback circuit and
make it switchable.

Also: the XOR gate fixes a little circuit "feature" whereby, depending on
which state the counters settle in when one input ceases, you might get the
squared sound of the other signal at the output OR(!) you might not get
anything.  This is because the AND gate can actually gate off the other
signal and an XOR won't.

Having no 74HC86s on hand, I went to Radio Slack to get one and they had
only 74HCT86.  I bought it anyway and it worked.  Does anybody recall the
differences between the 74HCxx and 74HCTxx series?

John Speth
Object Engineering, Inc
mailto:johns at oei.com