KEYBOARD ENVELOPE GENERATOR
pc board "env. gen"
Resistor code for the 3.3k resistor is ORANGE -ORANGE - RED - GOLD.
The best test of this module is its standard use, i.e. patched into a VCA to control an audio source, and triggered by a keyboard. To achieve this patch, plug a VCO into a VCA with the VCA's output being monitored over speakers. Take the keyboard's output trigger into the "gate" input of the KEG. If the keyboard is an ARP type with both gate and trigger, plug these into the appropriate jacks in the KEG. Testing of the KEG can now proceed.
First turn all knobs fully CW. Repetively key the keyboard as you do the following steps: Test the "all" knob by turning it CCW progressively. This should audibly lengthen rise (t1) and fall (t2) times. Now turn the knob for sustain (t3) until the sustain level drops part way.
Now turn the knobs at (t1,2,4) progressively CCW one at a time. This shouid result in the rise, first fall, and last decay times to increase respectively. To test the VC inputs, set the knob at (t3) fully CCW. Test by patching a variable CV from 0 to+5 into the VC input for (t3). Results should be a change of level. Un-patch the variable CV and set the (t3) to an intermediate level. Set t1,2,4 knobs fully CW. Adjust VC-all knob to a relatively slow envelope.
Plug the source of variable CV into the jacks at t1,2,4 one at a time. The CV should affect the appropriate slopes (rise, first fall, decay) by speeding these up as it goes from 0 to +5V. Un-patch the CV and leave the envelope slow. Patch the end pulse ("end-T2") into the VC input (t4). The decay time should change from its previously slow rate to a very speedy fall.
To test the "trig." input, first set (t1& t2) to a relatively fast spike, keeping the sustain level (t3) at a medium level. Plug a repetitive pulse source (such as a NEG. SLEW going twice a second, red jack out) or repetitively key the keyboard if you own an ARP, patching either into the "trig" jack. (tl & 2) should re-trigger audibly.
This completes the testing of the KEG.
NOTE: if you do not have a keyboard handy, all the above tests may be made using a relatively slow re-cycling NEGATIVE SLEW, plugging its sawtooth (blue) output into the KEG's "gate" jack.