Build Project: A Moog Melodia Replica

"What are you using for coil dope?" -Dewster 

I'm using a homemade brew of white polystyrene foam blocks broken up and melted in toluene.  I think it's essentially the same as the q-dope that you buy.  It dries fast and hard, although I think MEK as a solvent might make it dry even more quickly.

"Are the insulating tubes on the resistors and such stripped wire insulation?"

Yes, but I could have chosen better for heat tolerance.  Both types that I used tend to melt.  For my later mods since these pictures were taken I've just used colored heat shrink.

The red/black striped wire  was made by twisting white wire held in a vise with a drill, laying straight stripes down opposite sides using marker pens, then letting it unwind to form the spiral.  I wish I had figured out this trick back when I was hunting for different color-coded wires for my complex CNC panel wiring job.

Aieee!  100% bespoke down to the coil dope and the wire striping!  I wish we could both live a couple more lifetimes just so I could watch you build things.

I've finally finished a long-ish article on the complete Moog Melodia project here.  This was too long with too many images to post  on TW, but I'll be here for any Q&A.  

I've been playing it daily since I finished it on 12/6, and I think it's a good design.  It's stable and has excellent volume contouring with the unique end-plate antenna.  As I said in the article, if parts for this were readily available I think it would be an excellent design for first-time builders.  Bob Moog came up with a simple tuning procedure that requires only a voltmeter, and it's actually quite easy to make it work even operating blind without a scope or any more sophisticated equipment.

Anyway, check out the link if you're interested!

Wonderfull article! Especially the thouhts on the coilwinders and the fabrication of the coils are very helpful! This was a good read 

"Another characteristic of the Melodia that is similar to the Etherwave is the hypersensitivity of the pitch and volume adjustment knobs."  - pitts8rh (from the linked article)

This is a characteristic of variable caps right at the antennas, there is a 3-fold change in relation to the change in C due to absolute sensitivity variation along with the heterodyning frequency change.  Must make adjusting things pretty squirrely, and I can imagine that you have improved this with your padding mod.

Fantastic article (as usual)!  Nice to have someone with your EE and fab (and writing, and web, etc.) backgrounds doing it!  I found the voicing section particularly interesting.

(No one tell Roger he's playing a plate! ;-)

[EDIT] For the pitch preview, maybe make something that temporarily slips in there without altering too much, maybe connect with alligator clips or a dedicated connector of some type?  Snake a slim audio cable out the cracked open top?  Or bluetooth?

Roger – that is an impressive build! It feels like a time shift because you are creating something now and here which dates from the past. Sometimes, when i get a new old camera (or whatever) with one or more parts missing, i try to rebuild those parts mostly with what i have on hands. So it is fun to see, that you have all on hand and all the machinery and all the knowledge. How about the "Volkstrautonium"? Would that be odd enough?
https://www.youtube.com/watch?v=pOB6A26tfVY
Thanks.

Dominik!  I haven't talked with you in while.  I still love my Subscope btw, and although it's now part of a time-share rotation with the other theremins. I did spend about two months with it recently back in the front chair as my primary theremin.  I still say it has the best volume circuit of anything I have, and I don't expect to ever part with it, at least as long as I'm still able to lift and wave my arms.

Do you have any other information for the instrument in the link above (the thing with the name that sounds like a new element on the periodic chart)?  It doesn't sound electronic at all, and I'm trying to picture how it was done.  I'm also wondering what is the significance of the thyratron rather than a regular vacuum tube? The only thing that I thought those mercury-filled thyratrons and ignitrons were used for was for power control applications way back when.

Thanks for posting this!

Roger H.

Roger, thanks for your nice words about playing the subscope!

Unfortunately i don't have any special material about that desktop "Trautonium Ela T 42" which seems to be quite rare with the 200 units made by Telefunken. And no clue about vacuum tubes and such. The original Trautonium was the source of sounds for the croaking in Hitchcocks "The Birds". But i guess we all know. I have had the honour to be part of a group visiting Oskar Sala in his late years in his studio in Berlin. He even played some outer space tunes on that famous instrument.

If you ever happen to visit Berlin – at the museum of musical instruments the miniature Trautonium can be admired!