User Tools

Site Tools



This shows you the differences between two versions of the page.

Link to this comparison view

x0x:envelopegenerator [2016/01/28 18:05] (current)
Line 1: Line 1:
 +===== Envelope and Gate Generator =====
 +{{template>​.templates:​schema|section=Envelope|inputs=DigitalSequencer:​ Gate On/Off, Accent|outputs=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)