EW/EM theremin build report

Hello there,
About three years ago I was building a theremin and the community here helped me with the project.
I specifically remember something about people rarely reporting when finished. (Honestly I have no idea, what that was about *wink*)

Here's a video I made in the summer of 2017 as a convenient report form.

Short audio example starts at 0:52. (If you have perfect pitch, I recommend listening to it with audio muted)
I have some waveforms, that it produces on different settings, shown in the video.

The tuning of this thing was kind of nightmarish and the volume response could be a little better.
There is a little quirk, when you touch the pitch antenna, the pitch is so high, that it probably locks on to some other oscillations, making the pitch higher, which can be resolved by moving the hand far from the antenna, therefore introducing enough "force" to "rip" the audio signal away from this oscillation, returning to standard operation.
The video mentions high pitch which is audible in certain settings of the volume tuning knob.

If you have questions with your potential build, ask away.
I can't help that much with troubleshooting (I do have my tuning process written down) and how it works (for me, there is still some magic in it), but I might be able to help with the inductors I used, the hardware and should be able to provide my schematics, layouts and drawings.

Edit:
KiCAD files + some weird bottom and top layer of PCB hybrid + power supply and theremin schematic (the power supply has a ground lift switch, not shown in the schematic, should be possible to omit if recording through a DI box with ground lift, or not recording at all + using a non-grounded amp)
https://drive.google.com/open?id=1qAOFzKHJ1RQBQ26bM-Xo-V98v966E96r

Excellent presentation, woodwork and build.

Are you in the States?

Christopher  

Excellent presentation, woodwork and build.Are you in the States?Christopher

No, I'm from Europe.

The woodwork was quite a bit assisted, I don't have a well equiped workshop, nor the skills, so I had a relative cut the pieces out for me and after I glued it together, he rounded the edges and beltsanded it, so all that was left for me was to put on a finish.

"The tuning of this thing was kind of nightmarish and the volume response could be a little better." - IsawU

That's pretty much my experience with the EW too.  The Big Briar EW volume response seemed lamer to me, but the pitch side was less squirrely.

"There is a little quirk, when you touch the pitch antenna, the pitch is so high, that it probably locks on to some other oscillations, making the pitch higher, which can be resolved by moving the hand far from the antenna, therefore introducing enough "force" to "rip" the audio signal away from this oscillation, returning to standard operation."

An inherent danger, I think, of the EQ inductor approach to somewhat linearizing the near field.  I wonder if locating the EQ inductors on the main PWB is the best approach?  Perhaps stringing whatever is required out on some other substrate or mounting situation might work better, as it would allow you to mix and match whatever might be needed there.  It all seems rather touchy.

Thanks for the very nice video!  I prefer the way you have attached the pitch rod to the plumbing elbow crap on the Moog EW (just waiting to fall on the floor and break).  And your volume loop only having one attachment makes more sense too.

I prefer the way you have attached the pitch rod to the plumbing elbow crap on the Moog EW (just waiting to fall on the floor and break).  And your volume loop only having one attachment makes more sense too.

There is also one, thing that can be somewhat visible on the test chassis, regarding the conductive connection of the antennas, that I kind of like.

I use this kind of fitting for both antennas

and while the outside nut holds only the antenna, the nut on the inside holds the fitting in place and this little thing

that connects to the board itself and solder on the copper tubing works perfectly. The wire is not very flexible, but you don't have to move it once finished - I believe that original EW has a more flexible wire.

Perhaps stringing whatever is required out on some other substrate or mounting situation might work better, as it would allow you to mix and match whatever might be needed there.  It all seems rather touchy.

Perhaps, but I tend to dislike modularity in a device that can be sensitive to every minor change. If I ever find myself with surplus of free time on my hands I might make my own theremin (which I would understand more completely) and then I can get into experimentation.

"I use this kind of fitting for both antennas"  - IsawU

It looks like the brass ferrule is split, and mounted in rubber ring perhaps?  I imagine this makes it so you can tighten it pretty well with just your fingers?

It looks like the brass ferrule is split, and mounted in rubber ring perhaps?  I imagine this makes it so you can tighten it pretty well with just your fingers?

That is correct. The inside nut is tightened by a tool, since it rarely needs to be taken apart, and the antennas, which I demount for travel and storage, can be tightened by hand. It's not holding super tight - you can pull out the antennas with no special effort, but they won't fall off if you flip the theremin upside down and shake it in the air. The connection is properly conductive, even though I did not entirely expect it at first.

One thing, that I did not mention about having the small pieces of tubes in the fittings at all time, is that they also act as an end stop when inserting the antennas, resulting in (ideally exactly) the same antenna setup every time.

Hello there,About three years ago I was building a theremin and the community here helped me with the project.I specifically remember something about people rarely reporting when finished. (Honestly I have no idea, what that was about *wink*)Here's a video I made in the summer of 2017 as a convenient report form.Short audio example starts at 0:52. (If you have perfect pitch, I recommend listening to it with audio muted)I have some waveforms, that it produces on different settings, shown in the video.The tuning of this thing was kind of nightmarish and the volume response could be a little better.There is a little quirk, when you touch the pitch antenna, the pitch is so high, that it probably locks on to some other oscillations, making the pitch higher, which can be resolved by moving the hand far from the antenna, therefore introducing enough "force" to "rip" the audio signal away from this oscillation, returning to standard operation.The video mentions high pitch which is audible in certain settings of the volume tuning knob.If you have questions with your potential build, ask away.I can't help that much with troubleshooting (I do have my tuning process written down) and how it works (for me, there is still some magic in it), but I might be able to help with the inductors I used, the hardware and should be able to provide my schematics, layouts and drawings.Edit:KiCAD files + some weird bottom and top layer of PCB hybrid + power supply and theremin schematic (the power supply has a ground lift switch, not shown in the schematic, should be possible to omit if recording through a DI box with ground lift, or not recording at all + using a non-grounded amp)https://drive.google.com/open?id=1qAOFzKHJ1RQBQ26bM-Xo-V98v966E96r

Hello there! I have a question (I'll have many more but I want to go slow and steady) about the power supply, I'm clearly having a lot of trouble finding one suitable power supply for this project, perhaps that's why yours is custom made. Can you tell me please, if you built it yourself, which parts exactly did you use (specially the transformer, i have never messed with that), or if somebody built it for you, how to get in contact with that person? I'd really like to build this but I'm having trouble figuring this out.
Thanks!

Hello there! I have a question (I'll have many more but I want to go slow and steady) about the power supply, I'm clearly having a lot of trouble finding one suitable power supply for this project, perhaps that's why yours is custom made. Can you tell me please, if you built it yourself, which parts exactly did you use (specially the transformer, i have never messed with that), or if somebody built it for you, how to get in contact with that person? I'd really like to build this but I'm having trouble figuring this out.Thanks!
Hi,

The power supply is super basic.

Here is a photo of the internals. This should give you a pretty good idea of the power supply.

The transformer is BV EI 382 1194. Then a full-wave rectifier and L7812CV + L7912CV stabilizers.

I added the photo to the Google Drive link in my original post. A simplified schematic was already there.

Good luck with your build.

Hello there! I have a question (I'll have many more but I want to go slow and steady) about the power supply, I'm clearly having a lot of trouble finding one suitable power supply for this project, perhaps that's why yours is custom made. Can you tell me please, if you built it yourself, which parts exactly did you use (specially the transformer, i have never messed with that), or if somebody built it for you, how to get in contact with that person? I'd really like to build this but I'm having trouble figuring this out.Thanks!Hi,The power supply is super basic.Here is a photo of the internals. This should give you a pretty good idea of the power supply.The transformer is BV EI 382 1194. Then a full-wave rectifier and L7812CV + L7912CV stabilizers.I added the photo to the Google Drive link in my original post. A simplified schematic was already there.Good luck with your build.

That's incredibly useful, thank you very much. I'm a programmer myself and I have a little bit of experience building guitar pedals even following an schematic but my knowledge of circuitry is quite limited.
Could you please indicate the values of those 4 capacitors and those two resistors? Also I see on the simplified schematic there are 8 capacitors while on the image there are only 4, I wish I could figure that out myself but you know 

I see you also used some fuse maybe? The thing the blue cable is going into.

Also I live in Spain, here the wall plugs work at 220V, so I'm wondering if the same transformer will work in my case, since the stabilizers provide the 12 volts anyway and with only 10v difference the output of the transformer won't differ that much... I think?