[sdiy] Hacking the expression pedal input on a JD-800

[J. Larry Hendry]

Maybe you know this, but the Roland standard assumes ths the CV return to be
on the ring not the tip.  Yamaha uses the tip.  Therefore, if I wer
attempting CV into a Roland pedal jack, I would use a TRS connector, leave
the top open and have the CV feed to the ring through some resistance to
limit the current.
Larry Hendry

----- Original Message -----
> I've tried just connecting a CV source to the input, but that
> doesn't work. I'm not sure, but I'm guessing that this is
> some kind of current-loop interface; it expects to see a
> current flowing from the ring to the tip, so if you just hit the
> tip with a CV it doesn't draw current from the ring and
> therefore doesn't do anything. I'm thinking that I can use
> an optocoupler as, in effect, a voltage-controlled resistor
> to vary the current. I'm looking at the Fairchild H11F1.
> This is an optocoupler with a linear bilateral detector.