The recording is a snippet of a perpetual self-running patch. I like to limit some of the parameters, such as the chosen scale and post-processing effects for each take, to get a different feeling.

Undersea seems accessible to a lot of musical tastes, so I tried creating it again.  I replaced the MOTM-310 VCOs with MOTM-300 VCOs, but the patch is essentially the same.  However I neglected to make notes as to the settings on the Modcan Dual Quantizer and the initial ratio of pitches on the two oscillators.  I had to remember how to calibrate the automatic panning. Despite the lack of this information, the patch sounds quite like the original, but still unique in its own way.  I made several short takes of this aleatoric patch.  Here’s one.

• Mattson EG/VCA (2 modules)
• Mattson EG/VCA (2 modules)
• Dual Plague Bearer (2 modules)
• CGS Twin Wasp (2 modules)
• Mattson Distributor (4 modules)
• Mattson VC Mixer (1 module)
• CGS Super Psycho LFO (1 module)
• Dual CGS Slope Detector (2 modules)

That’s 16 separate modules in 8U of space!

The 1U panel dimensions are 8.75″ high by 1.725″ wide.  I leave it a little shy of 1 3/4″ wide to assure fit with other modules. I use this size for all 1U panels, not just this format.

The MOTM jack grid of 8 x 2 locations is ubiquitous. Vertical spacing is 1.0″ and horizontal is 0.85″.  I locate the lowest row 0.90″ above the bottom of the panel, which leaves clearance for parts both top and bottom.  Any standard panel component fits: a jack, a pot, an LED, a toggle switch, and even a miniature rotary switch.  Just make the hole the correct size for the part you’re fitting.

The main difference from the standard MOTM format is the small knob.  Although I happen to have used 16mm round Alpha pots for all of these, there is room to fit 12mm square Spectrol pots.

I generally put jacks to the right or below other components.  One reason for this is the use of Bridechamber 3-jack brackets to mount PC boards behind.  I like to use jacks to mount this bracket, but in the case of the Psycho LFO the bracket is mounted behind three pots.  Most of these modules are dual, with one module physically located above the other.  I try to co-locate a knob with its corresponding jack.  A CV attenuator will have its input jack just to the right.

A vertical column of eight small knobs has the downside that you have to look closely when grabbing one, to make sure it’s the intended one.  Naturally, a small knob doesn’t offer the same amount of control as a larger does.  (These are 3/4″ in diameter vs. the 1″ MOTM standard. )  I was willing to give this a try, as a trade-off for the module density, especially for use in the 20U portable cabinets.  I’ve proven the concept now, at least to myself.  Currently my DIY module queue is empty, but no doubt I’ll be considering the use of this format again for future modules.

Ken Stone’s Dual CMOS filters, a.k.a. “Twin Wasp” VCF.

Here’s a link to Ken’s description of the board.

Continuing the squeeze-it-into-1U-with-small-knobs approach, I designed this Front Panel Express panel for the Twin Wasp.  Key to the design is a miniature rotary switch, Mouser part #633-MRK-112A.  It’s single-pole, twelve-position, configurable to limit the number of positions to your needs.  At over twelve bucks a pop, it’s pricey.  But at least the knob is included.  The switch mounts in a quarter-inch diameter hole and even could fit in a slightly smaller hole, the bushing is that tiny.

Compared with the Bridechamber 3U Panel, the only features I had to give up were the inverted CV inputs and the spread CV, which is an external modification.  And mine is 1/3 the size!  I have created similar 1U panel designs for a dual CGS Steiner VCF and a dual CGS Serge 1973 VCF.  But I probably will not make those, because I have so many filters as it is.

The construction pic follows.  You need nimble, steady fingers to lay-solder the five wires to the itty bitty PC-mount legs of the rotary switch.  This filter uses four of the obsolete CA3080 OTA chips, the heart of so many 1970′s synthesizer circuits.  I was happy to finally use some of my stash of 50 that I’ve been hoarding for a few years.

I made one circuit change after taking the photo here. The FREQ pot sets the initial frequency. Ken Stone’s wiring diagram showed the CCW lug going to ground. But it really needs to go to -15V. And the summing resistor should be 270K or 300K, instead of the 100K on the schematic. I just added a 200K resistor in series with the wire going to the center lug on the pot.

I have to learn how to use this filter now!

The key to this patch is running the VCO’s initially at sub-audio rates.  At sub audio, the signal excites the P.B. to produce chirpy  sound.

Quantity:  2 in 1U

A pair of Flight of Harmony Plague Bearers, built into this small-format 5U panel:
Dual Plague Bearer

These are sold in a variety of packages.  See the Flight of Harmony Plague Bearer page for details and to download the manual.  I bought two barebones packs.  They will customize the order as you like with power connector, pots, connectors.  I didn’t order the pots, because I use panel-mounted Alphas.  What does it do? From the manufacturer:

It is designed to infect, corrupt and pervert a signal beyond recognition. It contains a Voltage-Controlled Resonant Bandpass filter that is designed with the goals of maximum signal alteration and maximum parameter controllability. Each filter has controls for varying the high and low corner frequencies of the passband, as well as variable gain and an input attenuator. Each section of the Plague Bearer can be used as a filter, an oscillator, a noise generator, or even as a resonance oscillator! Depending on the settings, the filter can be a lowpass, highpass, single-bandpass, or multiple-bandpass. Adjusting the resonance point can cause the filter to self-oscillate in many ways. By adjusting the controls to just below the point of oscillation, and then applying a pulse, square, or other abrupt-edged input signal waveform will “ring” the filter. A simple “click” on the input can give a percussive output sound – from bass drum to bell to a harsh metallic clang; Crank the controls up and this beast will scream like a banshee! The oscillation can be damped or continuous. Chain a couple in series and get accumulating feedback – the build-up can be slow, fast or instantaneous. White Noise is easy to do – you don’t even need an input signal! Turn the input all the way down, and then slowly turn the gain up. You can adjust the “color” of the noise with the frequency controls. Daisy-chaining multiple filters can give a “comb” or multi-phase noise. About phase-shift characteristics: A single filter can give a STRONG chorus effect if so desired, useful as a sub-oscillator or just to “fatten” a sound.

Construction

I butted the two PC boards together and mounted them to a Bridechamber 3-jack bracket.  It’s a nice, long bracket that left plenty of room for the jacks in front.  The P.B. boards each have four mounting holes, two on one end and two on one side.  I had to drill the bracket to match these.  The wiring uses headers on the board for all connections.  I like this, because if there were to be a problem, I could easily return a board for repair without unsoldering wires.

Although this model of the P.B. has a CV Gain input, I had to omit that in order to fit two of them into the 1U panel.  This is a little unfortunate, because the gain modulation produces interesting timbre changes.  Here’s a photo:

You can barely see the tiny surface-mounted chip!  These small boards are also low-cost.  Notice the two MOTM/Blacet/Oakley style 4-pin power connectors.  I made up a special power cable that jumpers them both.

Usage

I made a patch that uses them in the filter position in a nominally standard patch.  It’s called ‘Plague Birds’.  Look for it in the music section.

I used all of these modules and nothing else except the output mix. The weird tempo is the 320 LFO clocking the BZ, which in turn modulates the 320 frequency. I mixed and twiddled pots, mostly on the filters, during the recording.