Keyboard Mechanical Design

[John Speth]

Back in my hi-speed TTL design days of 1981 I designed and built a full TTL only 3 octave keyboard scanner similar to the one Gene mentions from EN.  I didn't experienc any timing problems - no PALs and I used LS TTL.  It scans fast and offers a 6 bit parallel output with a key gate. There is a high an low note  priority switch.  It's no big deal (but it works) but if anybody wants it, email me and I can help you get a copy of it.

John Speth
johns at oei.com

-----Original Message-----
From:	Gene & Debby Stopp [SMTP:squarewave at jps.net]
Sent:	Thursday, August 28, 1997 7:51 AM
To:	synth-diy at horus.sara.nl
Subject:	Re: Keyboard Mechanical Design

> From: Ken Stone <sasami at blaze.net.au>
> Subject: Re: Keyboard Mechanical Design
> Date: Wednesday, August 27, 1997 11:14 PM
> 
> Would you care to elaborate on your digital scanner? It sounds
interesting.
> I assume it remains a mono proposition, as you are wiring them into mono
synths.
> 
> Ken.

There is a circuit in Electronotes which works well - counter, 64-to-1 mux,
latch, DAC, with latching logic that latches either the lowest note or the
highest note, depending on which direction the counter is counting. The
lowest note case for example gives identical behavior to a resistor string
design such as a minimoog. I usually make it up as I build it, so they're
all a little different. The EN design was based around 1975-era TTL, and
has some timing problems if built with ACT/FCT parts or burned into an
Altera EPLD (for example), but some fiddling with the logic can fix it up.

- Gene