[sdiy] Keyswitches

[Stephen Lenham]

Hi Jim,

The original Practical Electronics Minisonic (c.1976) did exactly what 
you describe - it superimposed an HF signal (a few hundred kHz) onto 
the keyboard ladder and detected it to generate a trigger. This enabled 
them to use a stylus keyboard (though they went to a conventional 
keyboard for the Minisonic II).

The Minisonic II article was on the Cloned Analog Gear website but the 
links seemed a bit mixed up when I checked it today...if the worst 
comes to the worst then I have a copy somewhere.

The technique had better work, because I have a half-finished Minisonic 
;-)

As things stand it wouldn't retrigger if a second note was played but (
off the top of my head, without rereading the article) I don't see why 
the same technique used to make duophonic resistor ladder-based 
keyboards (i.e. detect the drop in level caused by pressing two keys 
simultaneously) couldn't be applied to the HF signal too.

I think I'd be reaching for a PIC before I did that though...

Regards,

Steve L. 


> Hi Group,
> How about a dumb newbee question to brighten your day?
> I was wondering if anyone had or knew of a circuit that made use of 
ONE set 
> of switches to generate both, the C.V. and trigger signal. The organ 
I am 
> going to use for my project only has one switch per key.
> I thought I saw a circuit that did this by superimposing an A.C. 
signal on 
> the ladder resistors. Another circuit detected the A.C. signal (or D.
C. for 
> that matter) and generated the trigger while sending the ladder D.C. 
to the 
> C.V. circuits.
> Am I crazy of would this work?
> Also what would involved in making it play more than one note at a 
time?
> 
> Thanks
> 
> Jim
> 
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