[sdiy] Re: did someone say "tube"?

[Ken Stone]

I've been thiking about your tube based keyboard with the tube sample and
hold problems. Perhaps you are approaching this the wrong way.

Instead of trying to capture the voltage, capture which key is pressed
instead. Use a neon lamp based latch, where only one neon can remain lit at
a time, then take your voltage from that via an appropriate divider or diode
"binary encoder" and a D/A resistor ladder. Sure, you'd need to use diodes,
though as this was common practice in a lot of tube equipment, I don't think
that it is cheating. Wurlitzer organs used a similar latching arrangement
for their organ pedal boards, though of course they were gating existing
pulse trains rather than deriving a voltage.

Ken
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au  
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>