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Lowrey GAKH-1 expression pedal set up as virtual organ expression pedal

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    Lowrey GAKH-1 expression pedal set up as virtual organ expression pedal

    Hi all

    The last component of my Lowrey Citation Theatre Spinet GAKH-1 that I wanted to use for my Lowrey / Hammond virtual organ is the expression pedal, which utilizes a photocell setup.

    The attached snippet from my Lowrey circuit diagrams shows how the expression pedal is set up in the Lowrey, using a 22 Volt source for the photocell. Having a 24 Volt power adapter available, I connected this up and tested the operation of the pedal across two of the output pins using an ohmmeter, it looked nicely linear and well-behaved. I then connected a jack plug to the same pins, and plugged it in to one of my midi keyboards that accommodates a variable pedal. I assigned the pedal to the expression pedal on my virtual Hammond expression pedal, and it works nicely - although it only starts operating at about halfway down the range - playing with the midi range got me a reasonable pedal action, albeit fairly narrow.

    I'd like to improve on this implementation, and it seems to me that if I put more light intensity through the photocell, I might get the pedal to register the variation a bit higher up in the range, but I'm not sure how much more voltage I can apply, if I'm already using a 24V supply in comparison to Lowrey's 22V source - although there is a resistor in their circuit.

    Any ideas on how I might improve this performance?

    Many thanks