Blog Post 2: Eurorack Accessories and Laser Cutter

I have been building a Eurorack modular synthesizer system, diving deep into its many sonic possibilities. “Eurorack” is a standard for control voltage and module width/depth developed by Doepfer and not a proprietary format, leading to modules of various origin and function to operate harmoniously within any number of custom setups.

However, despite a market occupied by hundreds of manufacturers of synthesizer modules, the modules are very expensive relative to their modular function, especially when compared to other digital synthesis solutions – $180 could buy an entire suite of synthesis software to make any sound imaginable on a personal computer, but in Eurorack it’s a reasonable price to pay for a module that simply outputs a bass drum sound.

Fortunately, there is also an open-source and DIY attitude among the modular community’s niche enthusiasts. In addition to releasing assembly-required kits, many module builders release circuit schematics and even sell naked printed circuit boards of their specialized units. So, once the basics of a modular system are in place, with a bit of electronics assembly skill and significantly less money, an enthusiast can expand their system at a fraction of the cost of buying an out-of-the-box module.

I decided to not attempt a complex kit for my first attempt at assembling a Eurorack module, but rather the simplest module commonly found in many setups: the passive multiplier! Patch cables usually send voltage only between two terminals on synthesizers, but a multiplier splits the signal to allow, for example, a control voltage envelope to control both an amplifier and a filter.  Fortunately, passive multipliers need no external power, they just unite multiple 3.5mm jacks to mirror the same voltage. Because of this, they can also be very narrow. I decided to make a multiplier with 2 circuits of 3 connected jacks.

First, I found the specifications from Doepfer for Eurorack modules that all manufacturers follow, and made a template for a laser-cut panel in Illustrator. I used a 2 HP width, with screw holes in the center of the panel rather than at the 4 corners. I could use this template, adjusting the width for different HP, for other future panels.

I also found the specification for the particular 3.5mm jacks by Thonkiconn I used so I could cut precise holes to seat the terminals. Though Doepfer (and many manufacturers) recommend anodized aluminum for their panel fronts, I used 1/16” clear acrylic sheet I had bought for other projects.

I outlined these cuts in 0.001 pt width red in Illustrator to tell the laser to cut out these holes. I’d have a serviceable panel with this design, but I decided to add some functional and decorative elements.

I “titled” it in the middle by writing "mult" in a fun font. Guidelines and numbers above the two groups of three holes indicate there are two separate multiplier circuits. Both of these are 0.001 pt blue strokes to indicate “deep cut” mode to the laser cutter. They turn out to be a little deeper engraved rather than just a light scuffing of the surface.

I also added some decorative lines that recall noisy waveforms by creating a rectangular grid and distorting it using Illustrator effects and a variable-width stroke. These ideally would just decorate the clear panel, and be distinct from the text/lines between outlets by being a shallower cut into the material. I left them black to be engraved normally.

From left to right: cuts, text/function lines, decorative pattern

When the laser cutter finished, the deep engraving and cuts worked, but the noisy lines were not visible. Perhaps the 0.05 strokes were too thin in the middle using the stroke profile (bulbous at both ends) to register on the material, especially cutting through the thin paper that comes on top of the raw panels.

 The cut panel with jacks, ready to install

The cut panel with jacks, ready to install

I made sure the cut panel could fit into my rack by screwing it into the rails. Then, I unscrewed the nut off one of the 3.5mm jacks and put it behind the panel, pushing out. It fit snugly into the hole without forcing. Even though the decorative lines didn’t work out, I’m happy that I got the measurements right on the template.

I then seated and oriented all of the jacks in the same direction.

 Seated jacks, ready to solder.

Seated jacks, ready to solder.

I soldered the pins of the jacks together with wire connecting the ground and positive pegs respectively in series.

 Soldering hookup wire between the jacks

Soldering hookup wire between the jacks

I tested continuity among each side using my multimeter, and then plugged in a patch cable to multiply the output of my MakeNoise 0-coast synthesizer clock trigger, a very useful function I really needed!

 Sending the clock output to the multiplier, and then back into the synthesizer to trigger both "slope" and "cycle" circuits.

Sending the clock output to the multiplier, and then back into the synthesizer to trigger both "slope" and "cycle" circuits.

As a bonus, I also cut out a 16 HP "blind panel" to cover some unused space in my rack. This time I used a pattern I generated in Processing and vectorized in Illustrator to cover it, and cut the whole thing in "deep engrave" mode. This was also a test for a future project using similar designs on acrylic panels.

 The blind panel in place.

The blind panel in place.

I also cut out of thick fiberboard a tabletop rack to hold all my patch cables. Nice!

 I think the laser was a little too strong or the material too thick, you can see the significant burning and carbon left on the inside fingers of the holder.

I think the laser was a little too strong or the material too thick, you can see the significant burning and carbon left on the inside fingers of the holder.

Blog Post 1 - Learning to Weave

I am experimenting with weaving textiles out of electrical wire; specifically, 2-conductor speaker wire. I'm interested in creating a functional "fabric" through which signal can be successfully conducted, and exploring how the ancient familiar form might be reconsidered when made out of an unlikely material. Moreover, I want to use the physical layout of the “fibers” in this configuration to exploit properties of electrical interference, rendered as sound from speakers attached to the textile.

Having never worked with weaving or fibers before, I did some research into different weaving techniques and found some tutorials on YouTube.

Woven textiles consist of both a “warp” (the vertical fibers strung around the loom, usually one continuous piece of fiber), and the weft (which weaves through the warp in a perpendicular over-under pattern in its most basic ).

My first experiment involved building a loom using a picture frame and nails (as described here), and using yarn for the warp and some spare 16 AWG speaker wire for the weft.

My first experiment involved building a loom using a picture frame and nails, and using yarn for the warp and 16 AWG speaker wire for the weft.

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Unfortunately, the difference in tension was too great and the warp snapped. The thickness of this wire was also a little too inflexible to get a tight weave. I also really disliked the way the yarn looked in combination with the speaker wire. I realized both warp and weft should be speaker wire. I had the revelation that I could then run two different signals through each strand and have them interfere with each other within the same textile (hopefully!)

I purchased some stiff cardboard notch looms, which could handle the tension of the wires, and thinner gauge speaker wire (24 AWG) to make a tighter weave. I used this wire for both warp and weft. The resulting textile was structurally sound and functional.

 The amplifier is attached to one end of the warp, and the other end of the warp to the speaker. I could also connect the weft ends to their own speaker/amplifier pair.

The amplifier is attached to one end of the warp, and the other end of the warp to the speaker. I could also connect the weft ends to their own speaker/amplifier pair.

When using yarn or other fibers, a weaver can use multiple strands in the weft, tying them off to the warp as they go along (this can create multicolor patterns or complex shapes, for example.) However, I am interested in getting a continuous length of wire through which a signal can pass.

The problem is that a continuous wire must be very long must be used to make even a small textile, and it has to be pulled entirely through the warp to get each row snug as the weaver progresses, which means each row takes a LOT of time. Furthermore, I found that the friction of the wire jackets on each other as I pulled the weft created some visible wear, so I have to be careful to pull in a way that minimizes the direct friction. Use of a heddle, a rigid piece that spans the width of the warp and elevates it, could help this problem.

Because of these problems, I quickly realized that I’d  have to work with individual pieces of wire and solder them together, covering them in heat shrink. In my first textile, I covered these connections with white heat shrink, as pictured above.

I don’t really like the way this looks aesthetically, so I tried to account for it in my second textile, by using these points to alternate to a different color wire. I was also trying to make sure that this point was close to the edge of the outermost warp wire, so it could wrap around and be less noticeable: 

 The heat shrink covers the beginning of the black strand. In this photo, both warp and weft are connected to speakers.

The heat shrink covers the beginning of the black strand. In this photo, both warp and weft are connected to speakers.

In further experiments, I think I will need to make these heat shrink joints an intentional part of the weaving pattern, perhaps using different colored heat shrink or having it expand over greater lengths than just the soldered connection.

Though these two textiles can carry two separate connections through both warp and weft, they don’t have the interference between the wires I was hoping for. In fact, speaker wire runs have to be either EXTREMELY long and/or situated next to an interference source like an AC main to really pick up any sort of noise, not just the sounds of two signals through two amplifiers. Furthermore, this doesn't even account for the increase in resistance as a wire gets longer, which makes further demands on the amplifier to be able to hear its output.

My next textile will be much larger, which will allow a greater length of wire and hopefully one more susceptible to interference, whether from ambient energy or the perpendicular signal.

I was talking with my friend Tom about his experiments with VLF recording ("Very Low Frequency" - the electrical interference in the magnetosphere that is in the audible range between 20-20,000 Hz). I realized I could make the warp a VLF microphone – essentially an antenna! I will warp my new, much larger loom with unshielded, single-strand copper wire, which has the advantage of being very flexible and thin. I'll solder on a TS jack and see if I can get some ambient sound, so at the very least, I can get some interference from the electrical grid from the warp.

Then I'll weave the speaker wire, or perhaps even another run of the wire as the weft, and see what happens! I would ultimately like to be able to choose the signals running through at least one side, so to add a layer of critical depth to the audio content (conceptually orthogonal recordings interfering within the weave). I might even try to add other electrical components or circuits into the weave – I've been watching the basic electronics course on Lynda.com to brush up on my circuits knowledge and generate some ideas.