CV Question

[amos_joseph]

I just got my sound lab up and running last night. By "knobbing around" on the panel without any external CV everything seems to be working properly, or at least it's making cool noises.

Here's my question: With a CV keyboard plugged in should the sound lab behave like a "normal" keyboard, only making noise when a note is pressed, or will it continue making constant noise like it does without any external voltage applied?

I've never played around with an analog synth before so I have no idea how it's actually supposed to behave. All I know is that I like what I'm hearing so far!

Thanks!
Amos

[mosc]

Monophonic analog keyboards generate a CV to control the pitch and a trigger to fire of an enevelope generator (ADSR), Without the trigger, the keyboard is just a fancy knob and would work pretty much like a knob on your synth's front panel. The trigger, also called a gate, is used to control the starting and stopping of the sound.

[amos_joseph]

So when I flip the switch to route my VCOs through the AR Generator in gated mode, they should be silent until I press the gate/trigger switch? Depending on what settings my AR gen is set to, that is.

If so then I think I need to look over my wiring. I'm getting a gradual rise and fall in pitch from the attack and release knobs, but it just returns to the same pitch it started at instead of the sound dying out completely. In trigger mode with repeat on I get a kind of "police siren" sound with my attack and release knobs both turned up a bit.

[mosc]

[Mike Walters]

Sounds like the AR is routed to the Osc 1 and 2 cv control. Like on Osc 1, if you switch the LFO on, you get the pitch modulation from the LFO. If you switch the AR on, you'll get a pitch modulation from the AR (pitch will move according to envelope curve).

I think what you want to do is route the AR to the the amplifier (VCA) to have the trigger control the over all volume according to the envelope, instead of the pitch of the oscillators. Also, you could route the AR to the filter, and the filter would open and close according to the envelope.

And by route, I mean turning the switch on/off on each function.

Also, your question about the keyboard triggering, I'll add to what mosc wrote. Yes, the CV keyboard should have a trigger out, and when routed appropriately (turn the AR ON on the VCA section, turn LFO on VCA OFF), will cause the amplifier to rise when a key is pressed (you also have to lower the VCA "Initial" knob a bit if you want silence when nothing is pressed). If you see on the schematic, it uses a transistor to close the same switch as the Manual Gate. The keyboard will produce the variable CV you'll want to (traditionally) route to the oscillators. The trigger out from the same keyboard just sends a voltage spike out which activates the SoundLab's AR circuit the exact same way as pressing the manual trigger. This is done usually by the CV keyboard having a separate bus on each key contact. So when you press down a key, you get 1 voltage spike (say +5V), and a variable voltage (say 0 to 6V) to send in as CV.

I hope I wasn't babbling too much!

[amos_joseph]