What exactly is the VCA destination?

[Pedr]

Note that there is a previous discussion here but it is a little bit lacking in detail.

On a superficial level I understand what a VCA is and would expect that setting it as a destination for an LFO would modulate the amplitude, but I'm a little bit confused with how this works on a per-voice basis. Is it modulating the VCA of all voices simultaneously?

Try this:
- Play 8 or 16 notes (depending on your number of voices)
- set one of the lfos to sync and to Random shape and set the destination to VCA
- set the Amount value to e.g. 40

Now I understand that each oscillator retains the last note value even after the the VCA envelope has completed, so passing a value to the VCA destination will still result in a note playing. However what I don't understand is what is happening to the individual voices. Although it does sound like different VCA values are being passed over, it also sounds like there is some cycling through the voices, with different notes playing out at different times.

Finally I don't understand how the VCA envelope ties in with the above. It seems to me that it's complete bypassed, but it also doesn't sound like there is no envelope at all, so what is being applied?

Note that there is no documentation as to what this destination does in the manual.

[creativespiral]

The VCA destination is going to drone all voices with the modulation amount applied.    So if you've got a 16-voice Rev2, then sending mod value to VCA is going to make all 16 voices be active/amplified at once.   

The best illustration is probably to start with an INIT patch, turn the Amp Envelope Amount completely down/off, and send a Modulation Matrix DC source to VCA, with amount of +127.   This will make all the voices active/amplified fully.   Now if you repeatedly tap a single key 16 times, all 16 voices will be playing that note, and more consecutive presses on that key will sound exactly the same.    Also, in this case of having DC+127 to VCA, you will notice the amp env amount control and amp env sustain have no affect on the sound, since the DC modulation has already maxed out the amplifier volume.   

If you apply some additional sound design which resets osc phase on each key stroke, or syncs an LFO to key strikes, then you will hear a voice retriggering sound.   Or, if you apply LFO to VCA like you said, if the LFOs are out of phase with each other, you will hear a repeating sound based on LFO phase differences...  the LFOs are polyphonic (LFO per voice).   If you have just turned on the machine, they will all be in phase, or if you turn on Unison and LFO Key sync and hit a note, they will all go back in phase... but if you ever turn on key sync without unison and press keys at different times, the LFOs will be out of phase per voice, so you will hear the patterns repeat.

[Pedr]

The way you are describing it is how I'd expect it to work, but if I carry out the steps listed in my post, I hear different voices (with different note values) come in and out. It certainly doesn't play all voices at the same time.

[Pedr]

Here is some audio: https://drive.google.com/file/d/186ZJPLoI4X3wLpwQBlZ-4u2hWk5Rxz56/view?usp=drivesdk

[Autosynther]

I think creativespiral meant that you set a bar at which env amount have no effect, it will be minimum as set for every voice when played. Not triggering all voices all the time.

I think VCA destination is the same as VCA Level in Misc parameters menu, and read manual about how that works. It also mention drone thing.

And remember that amount, velocity are kind of summed to determine how strong an envelope sounds. And for filter also key amount, as I understood it.

[creativespiral]

The way you are describing it is how I'd expect it to work, but if I carry out the steps listed in my post, I hear different voices (with different note values) come in and out. It certainly doesn't play all voices at the same time.

Yeah, that's because the LFO is polyphonic / per voice.   If LFOs are out of phase between voices and/or random S+H is selected, you will hear the per-voice LFO differences being transmitted to VCA / amp volume.    (16 different LFOs transmitting different random amounts to 16 Voice Amplifiers / VCAs)     

[Pedr]

Ah yes. Thank you. I have it now. There is an LFO per voice, and the LFOs are not synced. So they will either fluctuate independently, causing different voices to receive different VCA values depending on the LFO phase, or in S&H each voice will receive a different value, depending on the S&H value of that voice's LFO. This is why different voices drift in and out.

That leads me to another related question. Is there a way to sync the LFOs on transport start? I guess there are two kinds of syncing - syncing the four LFOs with each other, and syncing the per-voice LFOs with each other.

[creativespiral]

Ah yes. Thank you. I have it now. There is an LFO per voice, and the LFOs are not synced. So they will either fluctuate independently, causing different voices to receive different VCA values depending on the LFO phase, or in S&H each voice will receive a different value, depending on the S&H value of that voice's LFO. This is why different voices drift in and out.

That leads me to another related question. Is there a way to sync the LFOs on transport start? I guess there are two kinds of syncing - syncing the four LFOs with each other, and syncing the per-voice LFOs with each other.

Yeah, having a Global/Mono LFO mode has been one of the most asked feature requests through the years for Rev2 (and some other synths as well)... to be able to get that vintage type of character of synth with a single mono/global LFO.   

As mentioned above, you can do this trick where you temporarily engage Unison and turn on Key Sync on the LFOs, then hit a key, and that will synchronize all the LFOs to be in phase... then turn off unison and LFO key sync before hitting any other keys.   But with S+H/Random, each LFO will still have different random patterns, so you're not gonna be able to get that classic Camera Eye type of sound where a single random LFO controls cutoff (or other param) for all voices.   

[Pedr]

That makes sense. Thank you.

So the LFOs are free-running. Even when CLK-SYNC is enabled it only controls their cycle length, and does not synchronise their start. As soon as KEY-SYNC is enabled, the cycle for each voice starts with the key-down, allowing them to all go out-of-phase.

To bring them all back into phase and to sync the cycle start manually, you can switch into Unison and press a single key down, then switch back out of unison.

I actually really like the scope of this. I guess it would be useful to have a global LFO, but there are other synths for that.