| Music Gear Repair and Hacking /\ | ||
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I got this organ really cheap in the fall of 2009. It is solid state, but does a pretty good imitation of an older tonewheel organ like a B3. It has a little built-in Leslie speaker and all kinds of weird gadgets like an analog drum machine (which sounds a little like a TR-808), Symphonic Strings (which sound kind of like a Roland VP-330's strings), automatic chording, Fascinating Fingers II (an arpeggiator), etc.
I decided to add a MIDI Out interface to it so I could use it to control the Miditzer software. (Try the Miditzer...it's free and fun to play with!)
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I am designing the boards myself and programming a PIC 16F877 chip to generate the MIDI. The key contacts on the Commodore output about -20V when the key is pressed. I wanted to use CD4067 16-to-1 analog multiplexer chips, which cannot handle a voltage range wider than about 20 volts, to scan the keys into the PIC. So I am using voltage dividers to reduce each key signal to about -2V before it goes through the multiplexers. The multiplexer chips are running on +/- 5V power supplies generated by 7805 and 7905 voltage regulators from the Commodore's +/- 24V supplies.
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Here is what it sounds like when the organ is driving a synth in Reaktor: (1.4 MB mp3). The Hammond is doing the drawbar sound, strings, arpeggiator (sorry, FASCINATING FINGERS II), and drum machine. Reaktor is being driven by the top manual and is doing the analog-synth-like notes.
(Click on a link to see a page about that part of the system)
┌─────────────┐ ┌────────┐ │ │X1 X4│ Upper │X1 Ribbon │ │<────────>│ Man │<─────────── │ │ │ Mux │X2 Ribbon Wires soldered │ │ │ Board │<─────────── onto key boards │ │ │ │X3 Ribbon │ │ │ │<─────────── │ │ └────────┘ │ │ │ │ ┌────────┐ │ │X2 X4│ Lower │X1 Ribbon │ │<────────>│ Man │<─────────── │ │ │ Mux │X2 Ribbon Wires soldered │ │ │ Board │<─────────── onto key boards │ │ │ │X3 Ribbon │ │ │ │<─────────── │ │ └────────┘ │ │ │ │ ┌────────┐ │ │X3 X4│ Pedal │ │ │<────────>│ Mux │ │ │ │ Board │X1 Ribbon Wires soldered │ │ │ │<─────────── onto terminals │ │ │ │ on 'Ease of │ │ │ │ Play' board │ │ └────────┘ │ │ │ │ ┌────────┐ │ │X4 X5│ Upper │X1 X1┌───────────────────┐ │ │<────────>│ Manual │<──────>│ Long Button Board │ │ │ │ │ └───────────────────┘ │ │ │ 2nd │ │ │ │ Touch │X2 X1┌───────────────────┐ │ │ │ Master │<──────>│ Long Button Board │ │ │ │ Mux │ └───────────────────┘ │ │ │ Board │ │ │ │ │X3 X1┌───────────────────┐ │ │ │ │<──────>│ Long Button Board │ │ │ │ │ └───────────────────┘ │ │ │ │ │ Main │ │ │X4 X1┌────────────────────┐ │ PIC │ │ │<──────>│ Short Button Board │ │ Board │ └────────┘ └────────────────────┘ │ │ │ │ ┌────────┐ │ │X5 X5│ Lower │X1 X1┌───────────────────┐ │ │<────────>│ Manual │<──────>│ Long Button Board │ │ │ │ │ └───────────────────┘ │ │ │ 2nd │ │ │ │ Touch │X2 X1┌───────────────────┐ │ │ │ Master │<──────>│ Long Button Board │ │ │ │ Mux │ └───────────────────┘ │ │ │ Board │ │ │ │ │X3 X1┌───────────────────┐ │ │ │ │<───────│ Long Button Board │ │ │ │ │ └───────────────────┘ │ │ │ │ │ │ │ │X4 X1┌────────────────────┐ │ │ │ │<──────>│ Short Button Board │ │ │ └────────┘ └────────────────────┘ │ │ │ │ ┌────────┐ │ │X6 X1│ Left │ │ │<────────>│ Stop │ │ │ │ Switch │ │ │ │ Box │ │ │ └────────┘ │ │ │ │ ┌────────┐ │ │X7 X1│ Right │ │ │<────────>│ Stop │ │ │ │ Switch │ │ │ │ Box │ │ │ └────────┘ │ │ │ │ ┌────────┐ │ │X8 X1│ Piston │ │ │<────────>│ Mux │ │ │ │ Board? │ │ │ │ │ │ │ └────────┘ └─────────────┘
