A few other notes...

A SCN2651 Programmable Communications Interface chip on the main board generates the MIDI interface. An ADC0808 8 input 8 bit analog to digital converter sits underneath the microprocessor board. There is more glue logic on the main board but I haven't bothered to try and reverse engineer this or the function of the 8 bit ADC but I'm guessing it probably is used for string amplitude/envelope measurement.

A separate processor board is mounted above the main board and has a Z80 running at 4MHz. There's a 6264 8Kx8 static RAM backed up by a CR2032 lithium button battery. There is also an Intel P8254 programmable interval timer similar to the ones used to measure the string frequencies but it does not appear to be tied in with string measurement at all. There's also a 20 pin .3" center dip with a part number label on it. Probably a gate array of some sort.

Here are some pictures of the pickup mounted on the guitar.

A rant on "The Speed of Light..."

"Instead of antiquated magnetic pickups...the patented PHOTON pickup.....converts the string's frequency...faster than the blink of an eye."

Well I should hope so, the human eye blinks quite slowly actually.   

As an engineer, the marketing of the Photon always bothered me. The "speed of light" of this beast only applied for the short distance between the LED and photodetector. A magnetic or piezo-electric pickup has MORE than enough bandwidth to capture the fundamental frequency and several harmonics of guitar strings so the speed issue of audio-to-MIDI conversion is not in the pickup. It's limited by the cycle time of guitar notes and the fact that you pretty much have to measure at least a few cycles of signal before you determine the frequency and output the MIDI NOTE ON command. Who cares about 186,000 miles per second when a low E has a period of 12ms?

And MIDI doesn't work at the speed of light. Each byte takes 320µs to transmit and a NOTE ON is two bytes so that's 640µs plus processing time at the other end before the note sounds.

This isn't to say that an optical pickup is a bad idea for this application (ignoring the critical alignment issues) but trying to imply that it will generates MIDI notes faster than anything else out there is just plain wrong.

As a rule I'm not against accurate marketing to help sell a product but this is just bulls***. I did read that for an accurate reproduction of a string you should take measurements on two axis and that makes sense. And there is crosstalk in hex pickups that affects signal to noise. But MIDI conversion isn't about faithfully reproducing the sound of the string but determining its fundamental frequency.

Thanks for letting me rant.....