Build Project: A Moog Melodia Replica

Posted: 8/5/2019 12:48:35 AM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014


People please get a grip, the theremin is about a controlled flowing sound, not the look of a box with stencils. Add in a good Therminist and some will experience the magic of what it is all about. If something of value exists then post a sound sample. The theremin is a simple device.

Christopher

Posted: 8/5/2019 4:56:23 AM
gerd

Joined: 11/25/2017

I'm so impressed with your work, pitts8rh!

Posted: 8/5/2019 11:32:41 AM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

I appreciate the kind comments. 


"Add in a good Therminist and some will experience the magic" -Christopher

To oldtemecula, it's spelled "thereminist", and if you have something substantial to say, come out with it.  If all you can offer are these tiring passive-aggressive snipes, then I would invite you to vigorously GFY.


Posted: 2/21/2020 9:13:32 PM
senior_falcon

Joined: 10/23/2014

Absolutely beautiful build. It makes my original Melodia look kinda crummy by comparison. Maybe I'll get around to cleaning up the case one of these days. Have you added the electronic components to the case?

Posted: 2/22/2020 12:07:53 PM
pitts8rh

From: Minnesota USA

Joined: 11/27/2015

"Have you added the electronic components to the case?" - senior_falcon

Not yet, I'm embarrassed to say.  I still have to make something to do a correct honeycomb/progressive wind for the adjustable coils and the long fixed inductors. This is something that I have been looking forward to doing for a long time when I get a breather from the D-Lev project.  Even though I could have scramble-wound the coils by hand a long time ago, this Melodia project has always been about replicating the real thing as accurately as possible rather than just getting it done (even if it takes a long time to do so).

About two months ago I did get started with the progressive winder for the two fixed Melodia inductors by machining an encoder wheel and making an optical interrupter that I added to a 5C 3-jaw chuck mounted on a spin index.  The chuck would hold the long ferrites and I thought I could use the hand crank on the spin index to hand wind the coils.  The whole spin index was mounted on the table of a CNC mill, and the optical encoder was fed into the same encoder input on the mill that is normally used for the handheld encoder.

My idea was that I could just let the encoder pulses from the rotation of the hand crank push the milling machine table left and right to accomplish both the task of creating the honeycomb wind and the slower progressive movement down the length of the ferrite, all movements being dictated by gcode programming.  I would just feed the wire out from a simple stationary wire guide mounted to the head of the milling machine.

This all sounded good in my thought experiments, but during test it failed for two reasons.  First, the transport on the milling machine could not keep up with the rapid x-axis motion required for the honeycomb wind, and second, the bearing friction and the mass of a 4" rotating chuck completely obliterates any of the sensitivity that you need when hand winding something like #36 gauge wire.

One thing I did learn out of all this is that the CNC mill would be able to do the slower task of providing the lengthwise translation required during winding.  So the next plan is to build what is essentially a mechanical Morris Coilmaster type of geared arrangement to do the honeycomb wind.  This winder would be mounted on the CNC table to provide the slow translation of the honeycomb wind down the length of the coil, which I know it will be able to keep up with.  Since this is a one-use project I'm just going to 3D print up the gears and cams out of plastic.

So after all of these excuses the short answer is no, I haven't made any real progress on adding parts, but I'm looking forward to it because it will be like building a Heathkit when I get there.  Making the theremin work may be a challenge though, because my adjustable coils are going to be best guesses.  I don't think I know what the actual inductances of those coils are, and if you remember the ferrites that I used inside the homemade coil forms are just best guesses.

But thanks for your long term interest.  I'll get there, but I'm working more slowly these days.

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