Custom PAIA Theremin Build

For a recent class building project, I chose to take a shot at building my very own theremin. Such an instrument has always captivated my imagination and I hoped that by being able to build one cheaply that I would make a powerful gestural tool to use as a voltage control for other analog gear I want to build. I purchased the PAIA Theremax kit (minus the case) and began the process of assembling it.

Having built a Bleep Labs Thingamagoop LED earlier this year, this new project seemed daunting with much more parts and complexity than I had encountered before. My first endeavor would be to take inventory of all the parts to make sure they were correct. After checking for all the individual parts listed, it turned out the only thing I missing was a single 47k ohm resistor. I emailed PAIA about this and they immediately sent me the missing part.

PAIA Theremin PCB

Starting with the bare PC board, or PCB, I began by cutting small lengths of bare wire for jumper points designated by the directions. After soldering them in place, I moved on to the resistors.

PAIA Theremin PCB Wire Jumpers

There were more resistors than any other component in the kit, so this required quite a bit of back and forth between installing them and soldering them in place. After installing so many resistors, the back of the PCB gets cluttered and hard to solder, so I would install about 5-10 resistors at a time, solder them, clip the leads, and move on to the next batch of resistors.

PAIA Theremin PCB Resistors

I then installed the four oscillator coils, each of which had 7 pins to solder in.

PAIA Theremin PCB Oscillator Coils

Next came the capacitors!

PAIA Theremin PCB Capacitors

The types of capacitors used were both ceramic and electrolytic, the latter of which were polarized and needed careful consideration in the direction of their leads as indicated by the board.

PAIA Theremin PCB Capacitors

Next for the circuit came the diodes, which were also polarized and came in Zener, Germanium, and Silicon. I then installed the LM339 Quad Comparator and 748 OpAmp along with twelve 2N4124 NPN transistors. I was now ready to begin the wiring.

PAIA Theremin PCB IC & Transistors

I had found an old wooden magazine rack at Goodwill for cheap that I could modify to fit the theremin assembly. Knowing someone who works at a photography studio in a nearby warehouse, I made use of their tool closet to disassemble and modify the furniture into a case.

PAIA Theremin Wooden Case Modification

This required quite a bit of prying, sawing, drilling, cutting, sanding, and wood-gluing…

PAIA Theremin Wooden Case & Front Plate

But by the end at least I had a fairly authentic looking housing for the instrument!

PAIA Theremin Case With Wood Glue

At this point, I began to install the hardware jacks, various potentiometers, and SPDT switch into the metal faceplate that was then screwed into a wood panel I had cut a hole for it to fit into. I also drilled holes on each side of the case for the antennae soon to be installed.

PAIA Theremin Front Plate Back

Wiring up the theremin was a painstaking process, particularly when it came to working with connections to the lugs on the pots and jacks that I had pre-tinned beforehand. Cutting lengths of wire measured as specified in instructions, I also had to strip and tin them prior to connecting.

PAIA Theremin Wiring

Luckily, the PCB and instructions were very well labeled, so there was no confusion as to how the wires should be connected. Extra resistors between some of the pots and two LEDs for Power and Gate that also utilize current limiting resistors were installed behind the face plate.

PAIA Theremin Wiring

Soldering a main ground connection to a lug and screwing bolts onto the circuit to hold it in place, all I needed to do was solder the insulated wire to the antennae, the volume requiring a 1000uH choke coil added in between the wire and antennae. Having worked on this all night, I was excited to see if it would work.

PAIA Theremin Complete

Indeed the LED lit up, so I plugged it in to check the audio. At first there was no sound, so I looked in the instructions and realized there was a whole calibration process to get it going properly.

PAIA Theremin Complete

I then used a tiny screwdriver to twist the coils in the oscillators until they began creating sound. This was exciting as it turned out my project had been a success!

PAIA Theremin Complete With Stickers

In terms of sound quality, it does still seem to have a bit of high frequency leakage from the oscillators which is somewhat negligible compared to the main signal. I noticed the Moog Etherwave Plus theremin has a cleaner tone in this regard, with different oscillators from the Theremax. The Etherwave’s waveform control alters the harmonics, which sound like either a square or PWM oscillator at the extremes, and the Brightness control adds a filter that the Theremax lacks.

The Theremax does have more CV outputs than the Etherwave, with additional Mute and Velocity CV. However, the Theremax does not have a headphone output jack, as does the Etherwave. As well, the Theremax does not produce a pitch when you touch the pitch antenna, as opposed to the Etherwave which jumps to a solitary frequency. This can be a neat effect but is still not very practical, so not much of an issue either way.

The theremin I built works well with plenty of control voltage routing along with a gate to send out to external equipment. I’m glad that I built it and look forward to using it in my home studio, especially after building some more modular analog equipment to connect to it!

Building A Guitar Pedal Boost With Overdrive

Out of all the electronics projects I’ve been involved with lately, the construction of audio effects seems to be the most satisfying endeavor yet. Using the Karaoke Party schematic thanks to the “sharing is caring” DIY ethos of devi ever : fx, I was able to build this as my first guitar pedal, which you can see a video demo for along with details on construction after the jump.

To start out, I first needed to build the effect in prototype form. This required a protoboard to easily connect components along with the power supply I built earlier. Also, I needed to solder short lengths of hookup wire to the connection points on the audio jacks and potentiometers so I could have more versatility in the placement of connections. The other connections for various points were initially made using the same green hookup wire, but shortly after I discovered the wonders of using color-coded banana plugs for this instead.

KP Guitar Pedal Prototype

After double checking my connections for accuracy, I dialed in just over 9V on the power supply using my multimeter and hooked it into the power rails for the prototype circuit. Plugging in my cables, I flipped the amp on and held my breath. To my delight, nothing blew up and I actually heard the desired effect while playing my electric guitar through it.

KP Guitar Pedal Prototype

Hearing the effect work definitely felt like a mindblowing achievement, but I still knew there was work to be done for this to be converted into an actual guitar pedal. The next step was to try connecting a 3PDT bypass switch and LED indicator.

KP Guitar Pedal Prototype Cartoon

Using some more online tips, I was able to get this going so that it went into true bypass when the switch was pushed to turn both the effect and LED off. During this process, I also noticed how different color LED’s require different resistance values to alter their brightness.

KP Guitar Pedal Prototype with LED and Footswitch

Now that I had everything working in prototype form, I began fitting audio jacks, control pots, a DC jack, UV LED and 3PDT switch into the pedal enclosure. I didn’t start soldering the hookup wire to this gear until I had built the circuit, since having that gave me a better idea of the wire lengths needed. I also opted to use the many ground connections available on the PCB rather than attempt a “star-ground” coming from the DC jack negative terminal, as some pedal builders recommend.

KP Guitar Pedal Insides

The actual circuit was built using my prototype and the Karaoke Party schematic for reference, pushing the MPSA18 transistor, two .1μF (104) capacitors, and six resistors of sizes ranging from 10kΩ to 3.3MΩ into a through-hole plated perfboard PCB and bending the leads in such a way that they could be easily soldered to both the board and each other. I then painstakingly soldered these component leads point-to-point.

KP Guitar Pedal Final Inside

Now that I had the circuit ready, I knew both how long to measure the hookup wires to the enclosure gear as well as the available ground points left on the PCB. After cutting and stripping each wire, I would solder one end first to the contact points inside the enclosure. I also connected the LED in series with a 1kΩ Current Limiting Resistor (CLR). Once every contact point inside the enclosure had the right wire soldered to it, only then did I start connecting the circuit, since all the wires were cut fairly short to save space.

KP Guitar Pedal Final Off

Once everything was connected, the time came to see if it worked, and it did. I did some final touches before screwing the back plate onto the pedal, mainly clipping excess leads from the circuit and applying some hot glue to hold it in place so that it would not accidentally short to ground from touching the metal enclosure. Being my first pedal build, I spent many hours carefully working on it to avoid having to backtrack in such a compact device. I probably should have tested the circuit before connecting it to the enclosure, but I had been so careful that I felt confident enough to skip that step. To me, the most important factor seems to be careful planning so that you do everything in the right order for least difficulty in handling the assembly.

KP Guitar Pedal Final On

If I could go back and change something about this build, it would probably be to make the CLR a higher value so that the LED would be less bright. I am looking forward to getting more into the aesthetics and visual design of pedals, since this project was mainly focused on the technical aspects of pedal building. This was a fun exercise, although for the most part I would prefer not to build circuits point-to-point as it is fairly time consuming compared to using a properly made PCB for a certain circuit. I feel more confident working on electronics for audio after this and am thrilled to explore where this will take me next.

Building Project: Thingamagoop 2 RGB Portable Analog Synth Device

Just a quick post to show a recent build I did of the Thingamagoop 2 RGB kit from Bleep Labs. This device is a fabulous little noisemaker utilizing analog signals controlled by an Arduino ATMEGA chip, photocell, and various front panel controls.

Prior to sealing enclosure for Thingamagoop 2 RGB

The kit came with everything needed other than the basic tools to put it together. You can see the list of parts, schematic, and other info at the product page. It was a moderately challenging build, as it involves two PCB’s, a fair amount of parts, and plenty of soldering/wiring. A great project if you want to step up your game in the field of electronics assembly.

Close up of Thingamagoop 2 RGB circuit

Along with the 8Ω internal speaker, it has a 1/4″ mono audio jack for direct out and another 1/8″ C/V output to play other analog synths or modular setups using it as a controller. The C/V output is not the standard Eurorack 1 Volt/Octave but it really serves better for experimental improvising with sound rather than musical performance anyhow.

Thingamagoop 2 RGB Fully Assembled

Speaking of modular synthesis, I recently approached Make Noise founder Tony Rolando with my TG2 and he even let me patch it in to his modular setup, which was really cool to try!

Here is a video of me trying out the TG2 RGB immediately after putting it together…

Power Supply Assembly for Analog Effects Prototyping

Today I will be discussing the assembly of my newly constructed variable power supply, the C6724 by Chaney Electronics purchased from the site Electronic Goldmine. This device connects to a normal AC power outlet and steps down the typical 120 volts AC from the power outlet to safe levels that can be manually set anywhere between 0-12 volts DC. My main purpose for building this unit is to power analog audio effects that I have been wanting to try out using breadboard prototyping, which you should keep an eye out for in future posts.

1 assembly

If you are already somewhat familiar with the art of soldering, installing components correctly, and perhaps some fundamentals of electronics, assembling this unit will be a breeze. Since all basic parts and detailed instructions are included, you really only need your own soldering station with the appropriate soldering accessories (I ordered mine from Circuit Specialists), standard wire stripper/clipper tools, a phillips head screwdriver, and perhaps some kind of “helping hand” device to keep the circuit in place while you put it all together. Difficulty was rated 2/5 and I’d say that is a valid assessment of the challenge in building this power supply.

2 testing

The kit comes with a PCB, two 220μF 35V electrolytic capacitors, four 1N4003 diodes, a pigtail fuse, red LED, 1KΩ potentiometer, an NPN TO220 power transistor, heatsink for the transistor, 6.2KΩ resistor, 100Ω resistor, 4.7KΩ resistor, an on/off slide switch, the power transformer, stranded hookup wire, standard electrical cord, along with some nuts and bolts. All of the component values were accurate according to the measurements made with my multimeter. Along with the parts, it comes with fairly thorough assembly instructions, schematic, diagram of the unit/parts, troubleshooting hints, and a detailed theory of operation. All-in-all, a well thought out kit.

3 testing breadboard

In my opinion, the most important steps would have to be orienting the capacitor leads correctly, installing the heatsink onto the transistor using a screw without damaging the component, the red LED cathode lead orientation, the four diode’s cathode leads orientation, installing the fuse without damaging it, and measuring the right lengths of wire to cut. Such crucial steps are also highlighted in the instructions and diagrams provided within the documentation. You also want to make sure not to heat any of the components too much while soldering to avoid damaging them in the process. Some excess leads were also clipped off after soldering was done.

4 testing multimeter

After assembly, it did not surprise me that the unit did not turn on at first. I had done everything exactly as the instructions described, however the switch was not labeled to show which side was on/off, so it turned out that the connections to the lugs on the switch had to be reversed. After doing this, I was pleased to see the red LED came on for the first time and correct voltage values were measured by my multimeter! The +/- leads for the power supply were connected to my prototyping breadboard and successfully sent power through it, so I knew that this was now becoming an exciting and worthwhile venture.

5 enclosure

Suddenly not feeling very safe testing a power supply without any type of outer casing, I immediately took it upon myself to find an enclosure that would house this unit safely. Upon receiving the plastic enclosure, I thought out exactly how it should be implemented, such as placement of the potentiometer, switch, LED, and power wires, before finalizing the circuit placement within the enclosure using a hot glue gun. Have some sympathy with the results, as this was my first plastic enclosure build.

7 drilling

I began drilling holes into the plastic enclosure for the corresponding parts. The potentiometer and output power leads had standard drill bits, but for the switch and input power cord I had to first carefully measure the size of each and etched these proportions into the plastic with an x-acto tool before drilling small holes that were enlarged manually with a reaming tool.

6 reaming

Being very careful not to weaken or crack the plastic, I slowly expanded these dimensions until the related components fit into them just right. The on/off switch was a particular challenge in this regard, as the connecting wire I used for it was a bit shorter than I should have originally attached. However, after some struggle pulling it through the hole I did manage to get it installed properly.

8 enclosure top

During assembly, I did not realize that the red LED light could have been extended upward with wire so as to fit directly into the top LED hole on the enclosure, but I drilled a sight hole for it regardless. You cannot see when the LED is on from an angle at all really. At least looking straight down from above the red light is visible, which is useful to ensure that the power supply is turned on.

10 enclosure back

Once completed inside the enclosure, I was very satisfied with the result. However, something was still missing…

9 enclosure front

Ah, yes! No building project is complete without some nice aesthetic ornamentation. Here I decided to use an Obey Giant sticker with a hole in the mouth just big enough to let the LED shine through. The level of swag is now incomprehensible…

11 enclosure finished

That’s all for today. Be sure to like my Facebook page and follow me on Twitter for the latest updates! Check back soon for some upcoming projects using this power supply that will hopefully blow your mind.

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