Please note that I am not responsible for any damage you do to your theremin as a result of my blog. Hack at your own risk ! If you don’t know how to work on electronics or wood, ask a friend.

(Updated December 2023) This blog concerns the Moog Etherwave theremin. It deserves credit for being the pioneering modern “professional quality” mass-market theremin. It unfortunately suffers from a few errors in its design.

My wife has played this theremin in our garage punk band, Human Toys, for about 10 years. Experience has proven that the Moog Etherwave was not designed for use “on the road”. So I had to fix six problems, as explained below, which I did not expect to encounter in a €700 device made for professional use. Booo !!!

(1) A key problem is that the output is “line level”, not “guitar level”. So, if you connect your theremin to a guitar amp or play it through guitar effects pedals, the level is much too high, and you will get clipping and distortion. Booooo !!! I suspect many Moog theremin players are not aware of this.

I would say that this was an unfortunate engineering decision on Moog’s part. It presumably improves the signal-to-noise ratio, but at the cost of compatibility with standard devices.

In order to connect successfully to a guitar amp or an effects pedal, we need to reduce the output level. I give a big tip of the hat to the Big Briar service manual, which explains precisely what to do. Resistor R33, 4.7K, needs to be replaced with a 47K resistor. This has the desired effect.

PS If you are not using pedals, and do not want to modify your theremin, you can safely use amplifiers that have a “line” input.

(2) On this €700 device, Moog saved €1 by not having a power indicator. This is essential so that a musician on stage can rapidly verify that the power is arriving properly. How many times have Etherwave users set up on stage, found that there was no sound output, and wondered whether it was the power supply or something on the output side ? Booooo !!!!!!

I added a 12 volt LED across the power supply. (Available via the black and green wires on the front-panel pots.) I chose a 3mm LED and drilled a hole in the front panel for it. It’s in series with a ballast resistor, since the power supply is 14 volts. And doesn’t that look nice ! Now you get an immediate indication on stage when the unit is powered on. Of course you can pay €70 more and get the Moog Etherwave Plus which does indeed have a power indicator.

(3) The power supply connector is a three-pin DIN, although only two pins are used. Perhaps this was done intentionally to discourage people from plugging in other power supplies, but a DIN plug, with its small pins, is more fragile than the standard low-voltage connectors. Also, the mating power connector on the theremin is hidden inside the case behind the wood, making it difficult to orient and connect on a dark stage (or even a well-lit one). Boooo !!!

Much worse, the power connector on the theremin is simply soldered to the circuit board; there’s nothing to hold it in place except its three wires (no screws, etc.). So after a few years of constant use, the wires break where they are soldered to the circuit board and the theremin does not work. Booooooo !!!

I replaced the connector with a surface-mounted one that is screwed into and supported by the wooden case, so it is not fragile. And, being on the exterior, you can see the positions of the pins, making it easier to plug into.

(4) 2023, New problem : the theremin works intermittently. Diagnosis : The antennas are mounted on threaded pipe fittings that are screwed into the wood sides. This seems to work OK, although it’s kind of a hack. Then, to connect the antenna to the circuit, a small hole is drilled (diagonally so the screwdriver can reach it) and tapped (I think) for a tiny screw, which holds a metal star washer soldered to a wire. Well, that’s kind of a hack too, because in the best of cases the flat screw head and flat washer make a funky contact with the curved pipe fitting. Worse, the metal pipe fitting is rather thin at that point, too thin to hold the screw properly. The proof that it’s a hack : in my case, after removing the screw once and putting it back (during previous repairs), the threads stripped, so the washer was not held tightly on the pipe fitting, and moved ever so slightly when the theremin would vibrate (for example, touching the volume antenna with your hand, haha). This made the volume intermittent, it would cut out randomly. Very irritating. Boooo ! Solution : I soldered a wire directly to the pipe fitting (while the fitting was out of the theremin, to avoid burning the wood) and then screwed the pipe fitting back in and soldered the other end of the wire to the PC board. Now, rather than being held by the unreliable threaded screw and star washer, it is just directly soldered, does not move, and the problem is gone.

(5) After about 250 gigs, the threads on the microphone mount on the base of the theremin had literally worn away and did not hold on a mic stand any longer. I could not find an alternative that’s the same size, so I replaced it with the same poor-quality part, Atlas Sound AD-11B, available on-line for about 10€. (Actually I got AD-11BE, black.) I suppose I’ll be replacing it again in 10 years. I wish Atlas had not made it from cheap pot metal. I wish Moog had selected a better-quality part. Booo !

(6) The last area of concern is the wooden case. My wife dropped her theremin off a 6-foot (2 metre) stage, bringing to light certain design deficiencies. (Sorry for the blurry photo, where you can see the wood completely cracked into 2 pieces.)

Moog’s case design is clever because, with four screws, you can take the upper box off and then operate/test the unit when it’s open (see first photo at top of page). But the short sides of the lower box (where the antennas are attached) are not supported on their top edge by the case, even when it’s closed, so they are exposed to stress when the antennas move, or when it’s dropped. So the side panels crack. Boooooo !

What’s more, the short sides of the lower box are made of wood (rather than plywood) which cracks along the grain, precisely where it has been drilled for the antennas. If Moog had chosen plywood, this would be less of a problem.

Strangely, the front and back of the upper box are attached to the top with special screws and threaded plugs, rather than being grooved and glued. Presumably this was an attempt to make it stronger. The correct way to make the upper box strong is to complete the upper box with 2 more panels with glued dado joints on the inside (see photo below with post-it notes taking the place of these panels). If Moog engineers had paid attention in Wood Shop 101, they would know this. There is room for these panels to pass on the two sides of the PC board where the metal plates are. These two panels do not have to extend all the way to the base : they could pass above the metal plates. The upper box would be very strong. And they could save money on those funky threaded plugs. Booo !!!

However, those cool threaded plugs would find a much better use holding the top part of the short sides of the lower box, which support the antennas. I used wood screws instead (see photo below). Now the side panels are supported at the top when the unit is closed. I glued the cracked side panels, which seem to be holding up fine. If I had needed to replace these panels I would have done it with plywood as explained above.

Also, one of the wooden “feet” fell off. They are glued and nailed with tiny nails. A grooved joint (or screws) would have made them much more solid.

There you go ! Now we have a more usable, sturdy theremin that’s ready to go on the road !

Postscript :

When I first posted this blog on the Theremania Facebook group, another group member criticized what he considered theremin abuse, citing as examples a violin or a piano. I don’t recommend dropping a theremin, a violin or a piano, off a stage ! We do take care of our theremin, it happened by accident. But the example of a violin is flawed because the sound of a violin is directly related to its (relatively fragile) physical construction. On the contrary, a theremin can be constructed in a sturdy manner without affecting the sound ! The example of the piano is pertinent because, indeed, after centuries of refinement, pianos are designed and built so that they can be pounded on for years without falling to bits. This has permitted, in modern times, Jerry Lee Lewis to play a piano with his feet without breaking it. Whether this is a good thing is open to debate, but shall we tell him to stop ?

Falling off a 2 metre stage is extreme, but falling off a 1 metre mic stand by accident could happen to anyone — even you, dear reader, in your living room. Building the theremin with the standard techniques and good sense that I mention would result in a unit that would resist more common situations as well. This is why I believe my comments about its durability are reasonable. And I stand behind my other comments about numerous aspects of the design that could be better.

In parallel with the evolution of modern music and performances, manufacturers like Gibson and Fender succeeded by making their guitars and amplifiers more durable to stand up to contemporary use. This built their brands’ reputations and contributed to their success. I believe that Moog would serve their own interests by improving the durability and usability of their product in performance situations. Robert Moog is no longer with us, but I believe that as an honest engineer, he would own up to my criticisms.

Even if you debate my points concerning the wooden case, the power connector is a better example. Even children’s toys are better constructed than this. Imagine if the door handle of you car were held on by three thin wires. One day it would probably pull off, and you’d ask, “why didn’t Ford put this on with bolts ?”

And my points, when taken as a whole, show that the Etherwave was designed for static, home or studio use, and not for performance in public. Otherwise, why the absence of a power indicator ?

This story reminds me of the Vox Continental 2 organ used in my other group. This was a brilliant, innovative electronic design and sounds wonderful. But any Vox owner will tell you that the physical design is a catastrophe and it is constantly in need of repair : flimsy construction, fragile wires, etc. In 1965, the designers were clearly stuck in a mentality where the instrument would never go further than the user’s living room or a recording studio. Once in a real world of touring, the organ falls apart and becomes a liability. Later electronic organs are less fragile, and more practical for the real world.