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What is this undocumented module (QVCA)

#1

I seem to have a module I can find no documentation for. I have a VCA module, which is documented on the Wiki, and is a Quad VCA module, simple and easy to use, Audio and CV ins for each channel, but there is also a QVCA module that appears to be a Octal VCA but doesn’t seem to have any CV inputs. What is this?

Also I think I have read in a thread about panning, about using a -1 scale setting on a VCA CV in to inverse the control for simulating panning from one CV to two VCAs. I can’t seem to find a way to do this.

#2

QVCA is an example module that’s included in the SSP SDK.

Im surprised its in the image - thats possibly a mistake,
I assumes its in your ssp plugins directory (on sd card) , you can delete it.
thats why.I don’t document it on the wiki.

no its not an oct vca, its quad (Q) , that outputs a normal output and an inverted output.

outputs read :

    static String outputNames[O_MAX] = {
        "Out1", "Out2", "Out3", "Out4", "Out5", "Out6", "Out7", "Out8"};

but should read:

    static String outputNames[O_MAX] = {
        "+Out1", "-Out1", "+Out2", "-Out2", "+Out3", "-Out3", "+Out4", "-Out4"};

likely my mistake when I updated it a while back.

I’ll fix it, though I wont push the binary, because as I said, its kind of not supposed to be there…

#3

fixed on my fork of the sdk, also updated inputs to be in1/gain1, in2/gain2 etc.
no functional change, but I guess makes code easier to understand (kind of ;))

the simplistic approach to panning/crossfading is to use
n and 1-n , where n = 0…1

we can now say n = 0 , n=0.5 = centre, n= 1
(ofc, I can use pan = -1 to 1 for user facing, such that n = (pan + 1) / 2 )

you can then see sigL = sig * (1-n) , sigL = sig * n;

is this going to work?
well not in this form, but thats because the second part is detailing a linear vca (as qvca is)
and linear scaling is not going to sound right, you’d want a pan curve

a common one is to use sin/cos for right/left, but there are others
(even some daws will allow users to select the pan curve type)

however, the above IS useful for cross-fading esp, cv rather than audio signals.

BUT if you use an exponential vca, then it will kind of work, as the cv input is converted to an exp curve, which is another possibility for a pan curve.

edit: (updated)
I mis-remember, I thought VCA was exp vca, but checking code its a linear vca.

#4

I got my SSP used, like many of them out there, and am not sure where the libraries came from. The firmware number matches the latest release, so I never burned a new card. The previous owner must have snagged it from somewhere. I will probably erase it.

As for the panning bit, I have just driven both VCAs from separate inputs. I have lots of CV controllers in my rig and that is what I did when I used hardware VCAs. I was just trying for the most CV input available to use for other things. I have a ADDAC221 CV to MIDI CC converter though, so that adds 10 more. I haven’t tried it out on the SSP yet but it works great on my Nord G2.

I worried at first whether or not I would gel with the SSP, and found the patching daunting, but I have connected with it now. I am about to replace a bunch of modules in my live rig with it. Selling a bunch of VCFs and VCAs and maybe a ES-8 in my future. I will keep the FxAid Effects though - MUCH easier to dial those up than make them on the SSP.

Thanks for all the help - have a great new year!

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