[sdiy] Keyboard Circuit - Seperate Keyboard and Gate buses?

[Tony Kalomiris]

At 05:19 PM 2/24/2006, Gene Stopp wrote:

>You're right - you should only need one bus. The resistor string circuit in
>Electronotes (#45 or thereabouts) is a single-bus design that holds the
>busbar slightly negative with a very high value resistor to V-, and when a
>key is pressed the bus jumps to whatever that resistor tap in the string
>happens to be. A comparator watches the bus and when it goes above ground, a
>gate is generated for as long as the key is pressed. A FET-switch
>sample-and-hold captures the string tap voltage so it persists after the key
>is released. A differentiator watches the CV for any jump in voltage and
>generates a trigger as well.
...snip...

The MS20 keyboard circuit works EXACTLY this way, if I remember correctly.

Tony K 


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