Keyboard circuit (was Stretch tuning a resistor string)

[Harry Bissell]

The current source is the preferred method in most cases... I recommend taking
the output from the top of the string (nearest the current source) and having
the keys  ground the resistors. This way if you play more than one key the
highest (or lowest) key will dominate and they won't mix...

Or if you like quarter tones... (and you are not clumsy...)

:^) Harry (... like me...)

Tim Daugard wrote:

> Some one said use a voltage regulator for the keyboard resistor string.
> After thinking about it some more I had a few thoughts. SO tell me where I'm
> wrong.
>
> There are some benefits to useing a regulated current source instead of a
> regulated voltage source:
>
> The resistor string can be easily set for 1 volt per octave. Put the meter
> across the string at the octave points (one, two, three - doesn't matter)
> adjust the current source for the needed voltage drop across the resistor
> string.
>
> An adjustable resistor at the bottom of the string would allow adjusting the
> offset without having any effect on the tuning of the string itself. This
> means that just by switching in the proper resistors I can instantly change
> the octave (or smaller interval) of the keyboard.
>
> Add a transistor to the bottom of the string and I can instanlty add
> vibrato. All notes would be raised and lowered by the same amount, as the
> current through the transistor would just change the collector voltage and
> offset the string reference by a little.
>
> Is there good reasons not to do it this way?
>
> Tim Daugard