VCAs and LPGs

[grey]

It’s so aesthetically similar to X-Pan; that thinking seems on the mark.

[hermbot]

I wonder how much of a difference it would have made if they were able to get the Dynamix down 2hp to the same width as the Optomix. I actually would have bought one before if it had been a drop in replacement, even just to try it.

[_mark]

Wondering if anyone has any thoughts on the Doepfer A-135-2 as a general purpose VCA:

http://www.doepfer.nl/a-135-2.html

Seems like a bargain in terms of functionality and is also compact at 8hp. Any obvious downside?

[simonvanderveldt]

Looks pretty nice, especially for 8hp

Some observations from a quick scan, you be the judge if these things matter to you

• Only linear, no exponential nor a way to fluently go from one to the other
• Seems like the CV inputs aren’t normalized?
• I’m not sure, the text isn’t very clear, but maybe it doesn’t allow distorting the signal (text says the range is 0-1, not really sure what that means)

Btw the Antumbra DVCA offers 2 VCAs in 4hp so would allow for the same amount of VCAs in 8hp but you can then distribute them around your case if you want.

[_mark]

Thanks. I had seen the Antumbra and nearly bought one foo ebay last week. Similar is the other Doepfer A-130-2:

But the cost for two is a bit higher than the quad.

Quick question -

Seems like the CV inputs aren’t normalized?

What does that mean? in terms of usage?

[simonvanderveldt]

Ah, yeah, you’re totally right, I forgot about the A-130-2. It’s pretty new, Doepfer only added the slim modules recently, but looks pretty nice.
I haven’t tried one yet, so not sure about the knob spacing. I think I prefer the way it’s done on the Antumbra or on for example the Intellijel VCAs where the CV attenuator is a smaller knob leaving more room for the gain knob. But that’s personal preference of course

Seems like the CV inputs aren’t normalized?

What does that mean? in terms of usage?

It depends a lot on how you use the VCA/what you use it for. If you want to pass multiple signals through it that you want to control with the same modulation, let’s say an envelope, you only need to plug that envelope’s output into the first CV input and because it’s normalized to the other CV inputs that single envelope’s input can be used to control all other channels as well. And when the channels have attenuators for the CV amount you can still vary how much that shared CV input is applied to the individual channels.
Nothing major, but saves using a mult and some extra patch cables.
Alternatively you could mix the signals you want to control first so they only take up one channel but then there’d be no way to apply different amounts of the envelope’s output to the different input signals of course. Again it depends on what you want to use this for if this matters or not.
There are always multiple ways to achieve the same thing/something similar

This video shows how it works

It also shows the distortion later in the video.

[papernoise]

If you want to pass multiple signals through it that you want to control with the same modulation, let’s say an envelope, you only need to plug that envelope’s output into the first CV input

Sometimes I wish I had this, and other times I’m happy I don’t. The downside is: if you want to use part of the module the way you describe but maybe use one or two channels to do something that doesn’t involve CV control (like just attenuation or mixing) then you’d have to plug in a dummy cable. Pros and cons I guess.

[simonvanderveldt]

Yeah, you’re definitely right, it’s not always something you want.

I tend to put the channels I want to have under CV control at the bottom, so the channels above it are free to use for just attenuation without CV control.
And I guess alternatively one could turn down the CV control using the attenuator as well, but personally I almost never do that because then you have channels that are and aren’t controlled by CV arranged randomly which to me is a bit harder to navigate.

[_mark]

Thanks @simonvanderveldt and @papernoise - super helpful and all makes sense, only just got round to going through these replies…

[_mark]

Is there a VCA out there that gives you CV control over Linear to Exponential response?

[prussian_zen]

Alternatively you could go for a linear VCA and modulate the envelope from linear to exponential …

The ‘old’ MI Tides (2014) has a shape control, that is doing just that.
Or I think multing the envelope out back into the envelope time CV will change a linear into an exponential envelope. Add a VCA to control the amound of CV that is fed back into the envelope time CV. Not straight forward, but …

[rstn]

Double andore mk2 (which is a vca/env combo) gives you CV control of log/expo response.

[_mark]

Patch your envelope into Cold Mac’s crossfade circuit and then L and R out into the Tallin’s expo and linear ins.

That’s a nice idea. I’d looked at Tallin (like the xaoc stuff) and have Mac.

If I have an envelope that is linear and patch it to both in and level of a VCA, does that make it exponential? or quartic? or is that a multiply function… Just imaging trying to do this with a regular VCA and crossfader of sorts.

[grey]

Erica’s Pico Mod can be linear or exponential with a built in EG. It pings well, but can’t trigger the entire envelope without a gate; otherwise I like it. Sadly doesn’t work for my own needs, but it’s a very efficient module for the HP.

[ghost]

I’ve recently been using one channel of the sport modulator as an LPG and the other channel as an envelope. Add a VCO and you have a complete voice - Sounds just great. Such a versatile module.

[yittabitta]

Just got the Malekko Quad VCA (the only module from their Quad series in my case). It feels like the great mix of size and functions for me. Selecting and changing settings is very fast and the mute buttons are a great addition. Plus there’s a scan feature which is intriguing.

If you already have the Varigate 4+ it seems like a no-brainer as you can save presets but that’s beyond what I need it for.

[Henrycarden]

Fairly basic question, but is there any noticeable difference between processing CV in a VCA vs a LPG? Also if I’m processing audio from a modulator oscillator with an envelope to then send to the carrier’s oscillator’s fm, how would each affect the modulation? Would the filtering in a lpg affect the modulation vs a vca?

[dubiousphil]

If the LPG is vactrol-based, there may be some slewing of the signal, but that depends on how fast the cv is and how slow the LPG reacts. To your second question, I assume it would because as it got quieter, the modulation oscillator would lose high frequency content. Although that may only apply if your modulation signal has harmonic content above its fundamental (i.e. is not a sine wave). Your best bet is probably to try it out and listen closely to the results, both should be interesting!

[Henrycarden]

Thanks! I don’t have a vca right now, but I’ll ask some buds to test it out.

[chalkwalk]

A Vactrol usually has a minimum voltage below which the led has no output, similarly it has a “saturation” voltage above which it doesn’t get much brighter. This, combined with non linearity of the LDR means the response is quite different to a VCA. Similarly the amount of hysteresis/slew they exhibit can vary a lot. For some, a clock pulse will make a decay envelope, on some it just gently softens the edges of a gate, the latter being much more vca like. Often you can select how much filtering effect it has (from none to a lot) so for VCA like behaviour, turning the filtering off may help. If the modulation is slow and smooth filtering may have no effect (also the hysteresis/slew matters less in these cases). In short they can function somewhat like a VCA, but how close to a traditional (linear) VCA they behave depends a lot of the nature of the input and CV as well as the vactrol’s characteristics.