MATRIXSYNTH: By the time I got to Phoenix, I had a VCO.

Wednesday, February 06, 2019

By the time I got to Phoenix, I had a VCO.

Some background on STG's new .VCO via the STG SoundLabs Electronic Newsletter:

[Here's a crop from a great photo of the Radiophonic One system prototype in a cactus garden at Joshua Tree National Park. (Jill Gautreaux)]


"Finally ... I have a VCO.

So I sit here in a hotel room in Phoenix, waiting to hear from Southwest about my videographer's cancelled flight back to Chicago. It was already cancelled due to the crazy weather, and after rescheduling her flight has been cancelled again.

I thought I'd take this break in my drive back from California to let everyone on the list know that not only did I just show a VCO at the 2019 winter NAMM convention but that it is already for sale.

I really like using this Electronic Newsletter to talk about cool stuff going on in my life and then pitch something at you, however this time it's all pitch. To make up for it I'm going to insert some great photos from my trip out here and back. Some photos I took, some photos she took.

So my first VCO is actually going to be available initially in Eurorack format. Don't be too upset, it will be available in American format (or Moog format, or as some say "man-size") but for certain practical reasons Eurorack came first.

[Moustache Ride Bar & Grill, Amarillo TX. Looks legit.]

It's called the .VCO. It is 8HP in size, and has sawtooth, triangle, and suboctave square wave outputs.

It only has these three outputs because I already have a pulse shaper in the .COM/Pulse Matrix, and a sine shaper in the Wave Folder. I tend to think of all of my modules as components in a system so for me this makes a lot of sense.

It should probably be said right now before we get into it that this is an analogue VCO. There is a digital aspect to it in the tuning system, in fact there is even an ARM processor and a quad DAC in this thing but they are not in the audio signal path at all! They are just for tuning offsets, the drift generator, and scanning the knobs that control these things.

[Here's the full shot of Radiophonic One in the cactus garden. (Jill Gautreaux)]

The tuning system of this VCO is very exciting. There is a "range" knob which selects from LFO, octaves from 32' to 2', and a "wide" mode (more on that later.)

The next knob is "semitone" and selects an offset from zero to twelve semitones, and the fifth (seven semitones) is given a wider degree of travel to make it easier to set the VCO to this most useful of intervals.

The final tuning knob is called "detune" and when the range control is in the octaves has a bit more than a two semitone range. When the range control is in wide or LFO mode, the knob has a much wider range, measured in octaves. I haven't tweaked it to exactly what I want yet but I promise it will be as musically useful as it can be.

The next control is "drift rate." This VCO actually has an integrated drift generator!

[STG Soundlabs booth crew (Bubba Ayoub with Panamint Manse and Inhalt) with our new NAMM booth mascot, Stuffy. Coincidentally, our booth number was 11000!]

One of the really cool things about primitive VCOs from way back is that you would need to retune them because of temperature-related pitch drift. I thought "why not model that and turn it up to 11,000!?"

I originally conceived the drift generator as a random linear vector generator, inspired by James McCaskey asking me a long time ago "Okay so you have an LFO but what about a UFO?"

I thought about what a UFO would be in synthesiser terms, and backronymed it to Unidentified Frequency Oscillator. Another way of putting it would be a "random linear function generator."

[This is about 5 miles from Needles CA. That is not the sun, it is the moon.]

That idea got stored in my wetware about 10 years ago and it's been waiting for an application since. This presented the perfect opportunity for implementation.

Originally I just wanted the drift generator to be a random linear function, in both rate and amplitude. Obviously it would need to be bipolar.

However after a few days it occurred to me that maybe a linear function would be too harsh, and it would need to be smoothed. You can't just slew this function, because the frequency is random, so what to do?

[This is about 5 miles from Needles CA. That is not the sun, it is the moon.]

I decided to apply an S-curve to the linear segments, like running a triangle wave through a sine shaper.

This made the "drift" very smooth and the results are musically pleasing. I can listen to this thing drone for longer than I ought to be able to!

The rate control for the drift generator sets a master time period for the segments, which ranges from 30 seconds to 300 milliseconds. The random time variation is within 20 percent and 100 percent of that value.

The drift generator is normalised to the modulation input. This means that if nothing is plugged into the modulation input, the modulation knob will control the amount of drift, which at maximum is about an octave swing.

[Is it a tree or just a plant? I postulate that it's not a tree unless you can build a house out of it, so here I am with in between two Joshua Things. (Jill Gautreaux)]

There is a control input, which has the standard response of 1v/oct. However, the modulation input has a response of one half volt per octave. This is to allow for wide modulations from standard 5v control sources.

The third control input is a hard sync input. A cool thing about hard sync on this VCO is that the suboctave square wave is actually generated from the reset of the core, so it will sound different under hard sync than if it were counted off of a pulse shaper. It's kind of hard to describe quickly but just trust me.

I'm running a special low time preference sale on this VCO until my next Electronic Newsletter. If you order one or more now and are willing for it until summer you can get it for $200!

Act now and benefit from investor-level pricing!"

[Salt River Canyon in Arizona. Not even a fisheye lens can capture what an impressive scene this is.]

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