magical VCAs

[snigelx]

today, after some years, I finally learned what a VCA's purpose/role *really* is (esp analog synthesis)...Now, i miss the voltage modelling behavior for Env generators in many of the modeled synths around. Now I finally know how/why to use that fader on my J60

[Sendy]

It's there to control the amplitude of a signal by means of a varying voltage, no?

It also can add some level-dependant distortion, which can bring mojo to transients and make the amp envelope have some impact on timbre, which can really bring the signal from the oscillator(s) to life.

Anything else?

[snigelx]

It's there to control the amplitude of a signal by means of a varying voltage, no?

It also can add some level-dependant distortion, which can bring mojo to transients and make the amp envelope have some impact on timbre, which can really bring the signal from the oscillator(s) to life.

Anything else?

Yes, you see I thought I had an understanding of their usage before. I always thought it was an actual audio amplifier of some sort. This was wrong. I was reading Synth Secrets #9 (I never read the entire series, just bits and pieces I thought I was lacking) yesterday where I got an excellent explanation. Not far off from what you describe. The part I was amazed about was the part about how a VCA affects a "contour generator" especially as it relates to CV's like Envelope generators by affecting their total CV output (plus or minus). This has interesting affect on my Juno 60 when lowering the VCA to -5 and switchig the voltage switch on the back of the unit to H for high gain, I can get some very smooth contoured sounds. If I jack the VCA fader up to +5 and set the switch to M or L then I can get slightly sharper (at times slightly clipped) CV from the Env. Really cool revelation I had no clue about. Very important to understand every component of a synth. There are multiple VCA's in a synthesizer which -we know their control as- "Amount" (I'm guessing depth as well) faders/knobs. That was another revelation to me. So the "VCA" that we see labelled as VCA is usually connected to the output signal. Anyone into design should check out Gordon Reid's Synth Secrets 9. Now I am really interested to try more synthesizers with real CV behaviors. I think ACE exhibits a bit of same behavior with it's multiple VCA in the various modules

Seems like the VCA should be called Amplifier Voltage Controller or Voltage Control Amplifier and Attenuator.

Howard, do you have any wisdoms to lay on latecomers like me in this area??

[ghettosynth]

It seems like you've basically discovered simply that many VCAs can be DC coupled and, consequently, can be used to control the level of CV signals?

[spacecult]

I think ACE exhibits a bit of same behavior with it's multiple VCA in the various modules

It's marvelous how many different timbres you can get out of the ACE filter depending on how much signal you send into it.

This is something that took me a few months to figure out on an esq-1 because you kinda naturally drive the filter very hard with the oscs on that synth.

After I learned to turn the oscillators down I discovered there was a very nice filter in those things. Of course, sounds ok the other way, too.

[nilhartman]

It's marvelous how many different timbres you can get out of the ACE filter depending on how much signal you send into it.

Same goes for Diva. For example, try running your OSCs at very low volume into Bite filters...

[Dean Aka Nekro]

Pickup yourself up a copy of this book http://www.amazon.co.uk/The-Art-Electro ... 226&sr=8-1 and something along the lines of the suggested or similar pieces of test kit which an extremely good friend of mine whom happens to be electronics obsessed recommends here http://www.paulinthelab.com/p/test-geartools.html. Once you've got some fundamentals down through practice then you are free to find out a great deal. Maintaining your gear becomes so very much cheaper in the long run (In relation to what you will spend on tools). Also and perhaps the most fun part comes with building your own. I'm not suggesting it is for everyone but it is a lot of fun

[snigelx]

It seems like you've basically discovered simply...

I suppose, however the real discover for me was in relation to 'how' the 'levels' sound when they are altered by voltage level from, for example the VCA fader on my Juno. I always thought this was a secondary volume adjustment! I thought one would use this to tone down the gated signal and not so much with the env. Anyway, I never claim to know everything about a synth and I think it is worth sharing when I myself have been dabbling for quite some time with this stuff and missed this aspect. Perhaps there is someone else who did not get onboard in the age of CV.

It's marvelous how many different timbres you can get out of the ACE filter...

I agree! I was messing with this last night after I read about this. I haven't jumped into Bazille yet but I can imagine there are similar discoveries to be made there.

This is something that took me a few months to figure out on an esq-1...

Well now, I will have to get mine out of the house out back and take a look at this! I stored this board some months ago after sampling my patches (limited space). I will have to break everything open again just to check this out. Thanks for the tip. Wish I had a storage cartridge for mine, it came without

Same goes for Diva. For example, try...

Yes this definitely gives a differnet character to the signal although I -think- this is more example of actual tone gen audio signal fed into the nice filters causing various phase responses more than a CV control signal. Of course I should have check DIVA's output VCA first. But when I initialize to June-60 the Env gen is not responding in the same manner my Juno-60 responds when making adjustments to the "VCA" knob. I'll have to test again. Of course the VCA in DIVA must be in the chain before the Env gen because one can set the signal to pass through as Gate or controlled by Env gen. Hmm.

Do anyone else hear a change in the 'way' the Env responds in DIVA with lower or higher VCA setting when using Env? On the Juno I get a much more drawn out soft attack with low voltage long attack setting and slightly more pronounced and shorter long attack with higher voltage settings.

Pickup yourself up a copy of this book...

Thanks mate. Yes, I looked into this. A reviewer says it is outdated but that may not matter in the case of having this for old synth repair/maintenance. Do you own/use this book?? I imagine MUCH can be uncovered about analog synthesis by having a basic knowledge of electronics. Thanks for the tool link too.

[pdxindy]

It's marvelous how many different timbres you can get out of the ACE filter...

I agree! I was messing with this last night after I read about this. I haven't jumped into Bazille yet but I can imagine there are similar discoveries to be made there.

indeed!

[3*s]

Putting Diva in Minimoog mode, cranking the VCA gain and master level to max, putting 2 oscs at about 15%, and filtering a bit creates some very serious elderly neighbor scaring bass.

[3ee]

offtopic ontopic...

Diva VCA distortion:

Amp & pan section, that VCA mod slot that's usually empty...

-select add as mod source and mod amount to max, VCA vol to max also (lower output knob to compensate)
-mod section: set the add slots to gate + gate (or env1 + env1 if you have release)
-under the ladder filter (for more noticeable impact) set to 12db/oct mode
-feedback knob + filter res are your friends...

... if you set the filter kb track to max you will you can easily shape osc waveforms with the filter + feedback alone

... filter FM ..what?

added: under the modif. section, modulate filter FM with the add mod you've just set

[nilhartman]

3*s : IIRC from emails with Urs, Diva's Output knob is a simple volume control, with no non-linearities. So what you hear is the combined action of the filter and VCA.

[3*s]

The sound distorts differently with a lower VCO level; I mentioned the main volume knob as a way to make up for the low level. It's really obvious with the ms-20 module, but it happens with the Moog as well. I did an audio track comparison a while ago after I learned about the technique with the MS-20 filter, to make sure I wasn't hearing things. The waveform is indeed different.

It's possible that the low input level to the VCA is responsible for this effect and not the filter module, but regardless it's achieved by lowering the VCO level very low, driving the VCA, and using the main volume as a makeup gain.