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Envelope and Gate Generator

Schematic Overview:Envelope

DigitalSequencer: Gate On/Off, Accent

VoltageControlledFilter: Envelope
VoltageControlledAmplifier: Envelope

This circuit has 3 main parts, the Gate Circuit and the Envelope Generator and the Accent. The Envelope Generator is further subdivided into the VoltageControlledFilter envelope and the VoltageControlledAmplifier envelope

Block Diagram

<draw name=envblock namespace=x0x>

The Gate Circuit

The signal is incoming from the microprocessor on Q37 which seems to act as an inverting amplifier(?). It is then sent directly to the "Mono Multi" section of the Envelope Generator.

The signal from Q37 is also sent to Q36, another inverting amplifier. It is split at this point to the Envelope Generator at Q31 and Q32 and the Gate Out on the IoBoard.

The Envelope Generator

From Q37 (Gate) it is input into block called "Mono Multi", which is made up of a bunch of resistors, 2 capacitors and Q38. From here, the signal is split into 2, with one of them going to the VCA envelope, and the other going to the VCF envelope.

The Amplitude Envelope

After "Mono Multi", the signal is sent along a line called "trigger" to Q31 and Q32, and finally the VoltageControlledAmplifier. (duh. This section needs to be worked on…)

The Filter Envelope

Also from "Mono Multi", the signal is sent thorugh a diode, put through a 100K resistor, and then through a 1uF capacitor with the negative side leading to ground. What happens is that C62 gets charged up through the 100K resistor probably bu8lding the attack portion of the envelope. Then when the trigger is turned off there is no more incoming voltage, which causes C62 to discharge. This discharge, bedies going through to the envelope amplifier (see below) goes through a 68K resistor and then the decay pot. This bleeding of the charge causes the decay end of the envelope.

Q39, Q40 and Q41 make an amplifier to the signal before it is sent out to VR5 (env mod) and back into the VoltageControlledFilter (Q10, Q11). Q40 and Q41 make a DarlingtonPair, with the emitter connected to the Source of Q39. The Gate and Drain are connected together and then to ground. The emitter is also fed to the Env Mod knob, and finally into the VoltageControlledFilter.

The Accent

The gate operation varies widely when accent is enabled. On a normal note the MicroProcessor sends a positive voltage (+5?) to the accent line ending up at the base of Q35, which shorts the +12 V to ground. When accent is on, the accent line is low, which delivers 0V to the base of Q35 providing power to the 4066 analog switch. This switch shorts VR6 (decay) during the decay phase of the envelope so the signal goes stright into 138 and then ground, giving the accent its characteristic short-decay sound. The 4066 also shorts the connection to VR5 (env mod) and instead sends it through VR7 (accent), a diode, and a 47K resistor and ending up at the counter clockwise end of VR4 (resonance). The wiper of VR4 is input into the VoltageControlledFilter at Q10 and Q11. The clockwise end has a Capacitor that terminates at Ground. When the resonance pot is at the clockwise position, it charges the capacitor. This charging of the capacitor smooths off the envelope. After the voltage from the envelope starts to fall, it then discharges as well, giving you the rising accent sound. For more information on the sonic characteristics see TheAccent page.

/home/ladyada/public_html/wiki/data/pages/x0x/envelopegenerator.txt · Last modified: 2016/01/28 18:05 (external edit)