Wednesday, November 28, 2012

SSL Double Deka VCO -- first look

This beast is the Synthetic Sound Labs Double Deka VCO, based on the original design by Ian Fritz.  SSL just completed a limited run, which was marketed through Muff's.  The module, as you can see, is a three-unit-wide module in Dotcom (aka MU) format.  It takes power through a standard Dotcom 6-pin MTA-100 connector.  

To be honest, I'm not yet fully up on how this beast actually works.  As I understand it, the VCO proper runs in the ultrasonic range (around 100 KHz, I think), and it divides that down to produce square waves of varying ratios, which can be mixed in inverted or non-inverted via the banks of sliders that feature so prominently on the panel.  There are actually two, but they share a set of frequency control voltage inputs -- 1V/octave, variable-ratio exponential, and linear inputs are all available.  There is an octave selector for each bank, and a mix control for mixing the two banks.  There are a bunch of other control voltage inputs that I'll detail in a review after I've had a bit more time with it.

Before it's installed, let's look at the back:

We see three boards: the large board taking up most of the surface area of the panel appears to be the "main" board; it has some surface mount, and most of the panel controls are mounted to it.  The long board at the bottom mainly carries I/O jacks.  The extension board sticking out from the right edge is show in a better view below:

Interestingly, this board appears to be carrying the actual VCO circuitry, since the tempco mounted to the expo-converting transistor array is obvious if you look closely (under the blue trim pot).  The power input connector is also here; you can see it as the white component at the left edge in this picture.  That location caused me a slight bit of trouble during installation since it's near the top edge, and I had to bend the power cable some to keep the top cover from pressing on it.  

So how does it sound?  Well, I've only had about 20 minutes so far... It's a VCO that has a lot of capability for generating various timbres.  Adjusting the sliders has so far been a trial-and-error process; I'm still trying to find the design documentation (which doesn't seem to be present on Ian's Web site at the moment).  So far what I've managed to do with random tweaking has been mostly pulse-sounding things, although I have hit a few times on combinations that had the effect of greatly emphasizing certain harmonics (particular the 2nd and 3rd).  The fact that you have two banks, and that the mix between them is voltage controllable, creates possibilities for morphing between three timbres: the A bank, the B bank, and the timbre that results when the two are mixed.  (You can get a lot of cancellation between them, to the point of the output almost disappearing with certain combinations.)

There are modes for syncing to an external oscillator, which I don't quite understand yet; the terminology used on the switch is not the standard hard/soft selections.  There are control voltage inputs for making the banks change octaves, and a "ring in" jack that I haven't quite figured out -- it doesn't seem to be ordinary ring modulation.  I'm thinking what it might do is square up the input signal and then XOR it against the output.  

I think it's going to be a good module to have and to work with.  By itself, it doesn't zingy outer-space sounds, although I did manage to get a few weird things with external modulation.  There's undoubtedly a lot more timbral capability in the slider banks than I've uncovered so far.  And SSL's service was great; it took a few months to build this batch, but once they were ready and I paid my balance, I received my module within a week.  One minor complaint: no power cable was included.  Not a big deal to me since I have the tools to make my own.  Packaging was very good and my unit arrived in fine shape.  

And yeah, there are those cool LEDs in the sliders.