MOTM-120 Mod suggestion

[Arthur Harrison]

Hi everybody,

I think the "T" in "HCT" implies that the inputs of such devices are
voltage-level compatible with TTL logic.  I noticed that many vendors
are only carrying the HCT parts now, since (perhaps) they can always
substitute for the HC versions.  If anyone knows otherwise, please inform.

Art

-----Original Message-----
From: John Speth <johns at oei.com>
To: Synth-DIY List <synth-diy at mailhost.bpa.nl>
Date: Monday, November 02, 1998 4:10 PM
Subject: MOTM-120 Mod suggestion


>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
>
>
>