Casio MG-500 - Page 20

7 MIDI CIRCUITS
MIDI pickup converts the string vibration into current value.
MIDI Pickup
After inverted, filtered, and gain-controlled, the signal from MIDI pickup is separated in three
different signals.
(1) SIG——— For detecting the string frequency.
Integral circuit (A) eliminates the harmonics and, Comparator (@) turns the
ss! low paca eee
| for frequency detection.
extracts only positive portion of the waveform and, Comparator
heen tate (Chee Reser
For the velocity and note ON/OFF detection.
From Rectifier output, an integral circuit of a capacitor and a resistor extracts
the envelope signal only and, op amp (E) amplifiers the envelope signal.
(3) ENV
Actual waveforms at checkpoints ()~ ©) are shown on the next page.