After I received my Ciat-Lonbarde Tetrazzi Organ, I spent a lot of time delving into its design.  I wanted to understand it as well as possible in order to be able to play it well manually.  By design, Ciat-Lonbarde instruments are intended for play, as in fun, and their operation is to be joyfully discovered, rather than coldly reasoned out.  I like to play, but my brain also likes to figure out.  I used the paper circuit diagram, together with the schematic diagrams provided by Peter Blasser, and conducted my own experiments.  These then were my starting points.

Shown above is Peter B’s schematic for one of the four Tetrazzi oscillators.  It is an ingenious design for a voltage-controlled sawtooth/ramp oscillator, where the up and down rates are separately voltage controlled.  Not only are the rates under VC, each VCO has two modulation inputs, one for up (UPMOD) and one for down (DONMOD), that are hard-wired internally to come from the other VCOS.  The internal patch looks like this:

UPMOD cross connections:  [1 -> 4; 4 -> 3; 3 -> 2; 2 -> 1]
DONMOD cross connections: [4 -> 1; 4 -> 2; 2 -> 3; 2 -> 4]

The depth of modulation for UPMOD and DONMOD are under voltage control, all four being simultaneously controlled.  The different topologies for these two internal patches is the reason behind the different sound experienced for UPMOD vs DONMOD.   Did I just reveal a secret?  No, it is discoverable to anyone who takes the time to understand the paper tetrazzi.  If you click this image, save the GIF, and print it, you will have the paper Tetrazzi.

Functional Structure

The Tetrazzi consists of the following circuit elements:

• Four VCOs with VC up and down ramp, plus a solid state switch for additional modulations from node space
• Four “scroll” generators, track and hold circuits for establishing initial frequency and wave shape for each VCO
• Stereo VCA with inputs to each channel from each of the four VCOs, controlled by touch-sensitive piezo sensors
• A matrix of connections called node space for patching additional cross-modulations

The Tetrazzi Organ, built into the lovely wood case, provides the following means of manual control.

• Initial pitch and wave shape (the scroll) are set randomly by a red button, one for each VCO.
• UPTON pot controls the rate of rise, all VCOs
• DONTON pot controls the rate of fall, all VCOs
• UPMOD pot controls the depth of modulation for the rise rate, all VCOs
• DONMOD pot controls the depth of modulation for the fall rate, all VCOs
• Four wooden bars with piezo sensors attached control the stereo VCA
• Node space connections are made by touch or jumper wires

I took note that the pot wheels simply provide a voltage source.  I also noted that the scroll circuit simply provides a voltage.  And that the piezo electric sensors are voltage generators.   What I’ve done is to create a modular package for the Tetrazzi in which all of these voltage-control inputs are interfaced to standard modular levels through panel jacks.

I modified the scroll circuit on the board.  The scroll is now disabled.  The CV input goes into the on-board op amp where the scroll voltage used to go.  I used the XRS pad for a resistor that brings out the individual VCO output.  The SCR pad, originally for a capacitor, was used for a 100K terminating resistor.  See details by clicking on the schematic.

Adapter Circuitry Schematic

I designed interface circuits for

a) mixing CV from a panel pot with an external CV (8 of these),

b) buffering the VCA outputs up to modular level,

c) buffering the individual VCO outputs up to modular level,

d) creating a mix of all four VCO saw/ramp outputs,

e) creating a mix of the four pulse outputs that go into node space.

The CV input buffers also have the job of limiting the CV to the Tetrazzi board to safe ranges.  My design provides the following features.

• Pots for UPTON, DONTON, UPMOD, DONMOD, plus an attenuated CV input for each
• Pots to replace the scroll, one for each VCO, plus an attenuated CV input for each
• Four attenuated, AC-coupled CV inputs to replace the bars for controlling the VCA
• High/low range switch for each VCO
• Individual output for each VCO at 9 v p-p, bipolar
• Left and Right VCA outputs, bipolar
• Averaged sum of all the individual outputs (9 v p-p), bipolar
• Mix of the node space pulse outputs, scaled for modular use (nominally 10 v p-p, adjustable), bipolar
• Banana jack patch bay for the node space outputs (red) and inputs (blue)

So many patching possibilities exist I can’t describe them all now.  I will make MP3 posts soon.  I may also make a video demonstration.  Some things I’ve already tried that work well include patching an external LFO into the frequency inputs for vibrato or into the VCA inputs for stereo panning.  An envelope generator into the VCA control inputs works pretty much as expected.  And now it’s possible to tune the VCOs together with pots instead of randomly.

CONSTRUCTION

Here’s the Tetrazzi board (purchased by itself, assembled but I had to add the power components) with only the power input wired up for testing with the prototype adapter board.  Look closely and you can see the eight 1/8-watt resistors I added near the button connectors.  The circuit modifications were minimal, but I did have to cut some traces to disable the scroll circuit and bring out the individual outputs.

Here’s my adapter board, wired up on a prototyping board in the classic manner.

The back of the board with wiring.  It’s all hand-soldered, folks.

I built a jig from a piece of plywood to mount the two boards next to each other for the prototyping phase.

Panel assembly and wiring of the panel.

Wiring to the Tetrazzi board.  Some go to MTA connectors that hook to the adapter board and some go to the panel.

The Tetrazzi board installed and wired up to the panel.

Final assembly.

http://www.youtube.com/watch?v=4G8YPeT7r_U

Cocoquantus

The Cocoquantus from Ciat-Lonbarde is a most unusual instrument for electronic music.  Not many electronic instrument can claim, “materials include: Walnut, Sassafras, Juniper, Cherry, circuit board, transistors, capacitors, and resistors… “   Its inventor, Peter Blasser, describes it.

The CocoQuantus is a device by Ciat-Lonbarde composed of two Coco modules (8 bit digital delays) and a central “Quantussy” analog brain (nabra).

The Quantussy is a five (5) petaled flower, each petal with oscirator, that creates a rhythm, that triggers quantizations of the movements of the other four oscirators.  The Quantussy is thus both based on five (5), but four(4)… and its name also refers to Quantum Physics through its unique “double quantizing” of angular momentum.

Running at low frequencies, the Quantussy is intended to provide ample modulations for the various functions of the COCOs, through inputs “FLIP”, “SKIP”, and “SP.AF”, or “Speed Affect”.  The Quantussy petals can also run at audio frequencies, as well as “Balcium” frequencies, depending on a toggle switch.

The center of the Quantussy merits some attention.  There is a central indicator-lozenge of 15 Light Emitting Diodes, showing the “Spesal State” of the device.  The Spesal State is controlled by touching the “Cercel Nodes”, thus preserving Ciat-Lonbarde’s motto of “touch-sensitive is best!”.

To preserve this precious jewel of silicon encased in finest woods, use patch cords to wire it up in its own self-reconfiguring spasms.

These vibrations, spasms, activities, all manifest in unique transpositions and flip-skips in your material, which is input via Mike, Synthin, or special High Impedance Piezoin.  The COCO modules here have a generalized version of the DOLBY cargo-cult preamp, which includes a self-expander, and an other-puncher for maximum POP SENSATION MUSIC>

You see, on each COCO, there is a knob for INPUT as well as FEEDBA…  These are the primary functions of the COCO, to take in sound and recirculate it through *8BIT* digital memory.  These two functions INPUT and FEEDBA, depending on a toggle switch, can punch the others out to create monophonic articulations of time-layers in your material.

The instrument is ‘cottage-made’, according to the website. It is indeed a handsome artifact, each one custom manufactured for the customer. What can it do? The circuitry is arranged as a pair of 8-bit digital sampling devices, packaged with an ingeniously clever quintet of oscillators. It is a stereo device, capable of processing inputs of three types: mic, line, and high-impedance piezo electric device. The digital samplers are independent of each other. They feature various control inputs that are meant to be patched from the oscillator outputs (using jumpers with alligator clips, attaching to the head of screws in the wood panel, which act as input and output terminals).   Yet this is but one typical configuration. The oscillators can be patched into the line inputs, so that the cocoquantus will function as a stand-alone synthesizer.  The sample/delays are conventional enough that I could get the gist of them fairly quickly.  However the oscillators are more challenging to wrap your head around.

The ‘quantussy’ oscillator cluster is designed for complex cross-modulation. It’s going to take me a while to understand it. The design encourages jumping in and messing around, without having to understand it at first. It may turn out that trying to ‘control’ it will be a useless exercise. Briefly: Each oscillator has a three position range switch, high audio, low audio, and LFO. The five oscillators share two knobs, one which sets the initial frequency, and the other that adjusts ‘chaos’. Additionally, there is a control input for each oscillator that reconfigures its relationship with the other four. Each time the control input receives a voltage change, the configuration is randomly altered to one of eight possibilities, which are visually indicated by a combination of red, green, and blue LEDs in the central ‘petal’. Thus there are 8 x 8 x 8 x 8 x 8, or 32768 different configurations. A hand-drawn schematic is available, and I’ll be studying it in an attempt to find out just what these configurations represent. Now, each oscillator has two outputs. The ‘castle’ output is a result of sample and holding another oscillator at the speed of this oscillator. The triangle output is a smooth ramp up and down, which is modulated by the result of other castles, “re-castled”, when you turn chaos “up”. I looked at these outputs on a ‘scope. Once the chaos comes into play, they are quite unpredictable, but are following an internal logic. I was surprised at the variation in frequency resulting from the chaos. A given oscillator can go from high audio to LFO speed and everywhere in between, regardless of the position of its range switch.

Here’s a pic of the underside, showing the incredible printed circuit board that incorporates surface-mounted components.  (Note the nine-volt battery connector, nice for portable use.  It can also run off a 12V wall wart, not supplied.)

Cocoquantus underside

And here’s another photo of the top of the instrument.

Top side view

A picture of my studio in August, 2011.  Left to right across the table are the M-Audio Axiom 25 MIDI controller, the Macbook Pro running Audio Mulch software with an Uhbik VST plugin, the t.c. electronics desktop konnekt6 firewire interface, and the rack holding the Furman PL-Plus II power conditioner, the dual FMR Really Nice Compressors, the Lexicon MPX-1 Multi-effects processor, and the Tascam SS-R1 compact flash recorder.  The Mackie 802-VLZ3 mixer sits just behind.

• 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.

The other idea was to let some audience members in a close setting participate by using hand-held controllers like the one in the picture to change the sound during the performance, in effect jamming with me.  To this end, I put together the ‘west coast’ box in the picture, containing:

• Cynthia ZerOscillator
• CGS Wave Multiplier and Grinder
• Blacet/Wiard Miniwave
• Two CGS Serge VCS
• CGS Super Psycho LFO
• Dual CGS Slope Detector
• MOTM-800 Envelope Generator
• MOTM-190 Dual VCA
• MOTM-OMS 820 LFO/EG/Lag
• My own Matrix Mixer

I arrived at this combination of modules after a lot of consideration and trial.  The Matrix Mixer allows me to do the mix live without needing an external mixer.  The outputs can go directly to powered speakers.  I was looking for signal purity in this patch and designed it to avoid the need for external mixers, effects, computer interfaces, etc..  I can still run it through any of those if I want to.

The patch shown in the photo uses 9 modules:  the ZO, Wave Multiplier, Grinder, Miniwave, Matrix Mixer, a VCS, a VCA, 820, Psycho LFO.  And only 10 patch cords are used,  not counting the hand controller.  The Slope Detectors and MOTM-800 weren’t used here.

Three signal paths are patched.  1) ZO sine wave through the 190 VCA into the Miniwave (on the Socket Rocket EPROM), 2) ZO morph (variable wave shape) output through the Grinder, 3) ZO triangle through the Wave Multiplier.  The VCS is used as a VCO for linear through-zero modulation of the ZO.  The Psycho LFO modulates the Wave Multiplier.  The 820 is used as an LFO on the VCA to control the depth of the sine going into the Miniwave.  Everything else is hand-twiddled.

This is a performance:  There are no chance elements, only the combination of oscillators and manual operation.  I was pleased with the range of sonic possibilities available from this simple setup.  The title refers to the use of the center position of the BIAS switch on the ZO, which starts the oscillator at zero HZ with an infinite modulation index. Some sections use this setting, while others do not.   The telltale sign of non-zero bias is a more strongly pitched result.  It may be of interest to note that I did not touch the big ZO frequency knob.  Glissando effects all originate in pitch changes of the VCS.

I came up with an idea for audience participation.  It involves handing out two or three controllers to audience members at a live concert in a close setting.  Each controller is patched in somewhere and the participant has to figure out by listening what his/her controller impacts.  Of course I decide in advance what parameters are controlled and set limits on them.

The controllers patch using an insert cable with a TRS plug on one end that breaks out into two cables with TS plugs on the other.  They are color coded red for the input and blue for the output.  It’s like having a pot in the middle of a patch cable.  The big red button has to be held down to enable the pot.  By default, the output is at ground.  When the button is pressed, the output connects to the pot wiper.  So the participant can choose to hold the button and sweep the pot, or to set the pot and press the button to jump to the the pot setting.  I have a couple of 18-foot insert cables, plus a 6-footer for use in the studio.

The enclosure is a Bud box from Mouser, #563-AN-1300.  The button is NKK, Mouser # 633-LP0115CCKw01C.  Pot is an Alpha, Mouser #313-1000F-100K.  Everything fits snugly.  The button makes a loud click, which might be distracting if the passage is quiet.

• Mackie 802-VLZ3 8-input mixer
• Lexicon MPX-1 Multi-effects processor
• TC Electronics Desktop Konnekt6 Firewire Interface
• TASCAM SS-R1 Compact Flash MP3 recorder
• A pair of FMR Really Nice Compressors

Of the many potential ways to hook this stuff together, I’ve come up with this patch.  Have a look at this block diagram.

I’ll describe how this works with the Mackie features to get flexible signal routing.  The first thing to look at is the Matrix Mixer in the upper left.  This is my own Matrix Mixer module.  It can mix up to six signals coming out of the modular and has stereo outputs.  (Most of the arrowed lines on the diagram indicate stereo connections.)  Note how the output of the Matrix Mixer tees off, one branch straight into the Mackie on channels 3-4, and the other going through a compressor and the Lexicon in series into channels 5-6.   Both the compressor and the Lexicon are stereo units, and each has a bypass switch.

Moving down the diagram, note the mono Aux Send output.  This is not pre-patched.  I use it to send signals into the modular for any purpose, but usually to patch modules as effects.  The MOTM-410 filters, Blacet Time Machines, and Blacet StonZ Phaser make very good effects processors.  The outputs from whatever I’ve chosen are then returned to the Mackie channel inputs 1-2, which have equalization and also the ability to mix back into the aux send bus for feedback!

Next, notice how the firewire interface is fed from the Alt Outputs of the Mackie, and is returned on channels 7-8.  I have to explain the alt outputs.  Each input channel on the Mackie has a Mute-Alt button.  In the normal position, the channel signal is routed to the main mixing bus, headed ultimately to the tape recorder and the studio monitor speakers.  But when the Alt button is engaged, the channel is routed to the alt out bus.  The channel fader still controls the level, but now on the alt out.  This means I can mix to the computer any of the three sources:  from Matrix Mixer, from Lexicon effects, and from modular effects.

Remember that each Mackie channel also has an aux send pot that mixes into the Aux Send bus.  (Selecting the ‘pre-fader’ option sends the signal to the aux bus before it reaches the channel fader.)  Are you getting the picture now?  Possibilities include:

• Three parallel effects:  Lexicon, Computer, Modular.
• Lexicon and/or Computer effects followed by a Modular effects.
• Modular effects followed by Computer effects.

A few things I can’t do, such as routing the stereo output of the computer to the stereo input of the Lexicon.  (I have to mix channels 7-8 to the aux send and patch the mono aux send into the Matrix Mixer for that routing order.)  This setup has flexibility that I could have used even before I got the firewire, if only I had thought of it.  I hope this information may be useful to you.  And please add comments!

Getting the Macbook Pro opened up new possibilities for software DAW work, since it is such a great multimedia platform.  All I needed was a way to get audio in and out.  After some research I settled on a TC Electronics Desktop Konnekt6.  It provides two channels in and out.

Desktop Konnekt6

The Konnekt6 comes with Cubase LE4 and nice control panel software.  I really like all of the hands-on control this unit offers.  There’s even a button on the control surface that minimizes and maximizes the control panel on the computer screen.  The big knob is the volume control for playback, as it’s often connected directly to monitor speakers.  I route the output of the Konnekt6 back into my Mackie mixer on a stereo input channel.   That way I can play it back and record it into MP3 on my Tascam, and even add effects from the MPX-1 at that time.

Cubase LE4 is overkill for my needs.  I find it as daunting as Pro Tools was to use, and I don’t have much fun figuring out how to make it do what I want.  The neatest feature I’ve discovered is the built-in VST effects.  I do like to use digital post-processing, for which the Lexicon MPX-1 goes a long way.  Now I’ve got more to explore, if I can find the patience.  In any case, the whole setup works quite well and the Mac interface is great, especially the touchpad!  Not much need for a mouse any more.

Here’s a photo of the setup:

I wanted my own PA system for performances, so as not to depend on house PA systems.  So I purchased a pair of these RCF powered PA speakers.  The RCF is seen below a Mackie HR824 nearfield monitor.  I am able to use either set of speakers – or both at once – in the studio.  The RCF pole-mounts, too.

The ART 310-A speaker is bi-amplified:  300 watt low and 50 watt high into a 10-inch woofer and 1-inch tweeter.  Uses balanced XLR input with a through XLR output (handy for hooking up the Mackies).

How do these sound?  Really good!  The Mackies seem to have more definition, but not as much open quality as the RCF.  The speakers sound different from each other, but it’s hard to describe.  The RCF exhibits a little hiss from the tweeter when quiescent.  But I have no complaints.  They will do the job in a club or gallery.  And they are light:  under 30 pounds each.