Finding that pleasing illusive sweet note

This is my first post on any Theremin forum. I have read many of the posts on the TW forum(s) and I want to start by saying that I am sorry to have missed corresponding with Fred M. It almost seems like I have after reading his plethora of exchanges with many of you.

 I have a specific request st on any Tthat I will get to in a moment. First my motivation for this question. I teach a lab course at UW Madison ECE Department. Last semester I changed the required advanced circuits lab from designing and building a temperature controller to simulating (LTSpice), prototyping and building (SMT and PCB) a Theremin. This seems like a good fit as the Theremin has so many interesting circuits to work with. Last semester went better than expected. Everyone got the pitch and amplitude control to work. And they get to keep the Theremin. For next semester I want to change the Theremin circuit board to fix some errors and enhance the sound of the note or rather give options to enhance the note.

 Presently the note starts as a fairly low distortion sine wave and a square wave generated from the sine wave. They can be combined in an amplitude adjustable fashion. In my opinion this does not generate a pleasing note.

 I have studied this forum and other websites during the lab design. I see that some people enhance/promote/utilize the generation of the note with a non-linear mixer which as you know adds harmonics to the note in a hopefully  pleasing way. I prefer to apply analog processing to a low distortion sine wave note. Mostly because it is something that works well as a subject for the lab. I can have the students introduce non-linearity in the mixer that we use. I am reserving this for more advanced playing with the Theremin in the lab. I am not trying to bastardize the Theremin by having the students do experiments that are kind of Theremin like. I am also not trying to have them design and the build the best Theremin ever.

 I read the spectral makeup of a few classical Theremins in these forums and I am looking for more information with spectral content and examples of the sound. Any links would be greatly appreciated.

 I have prototyped some circuitry to try to do some analog signal processing on a low distortion sine wave. This is what I have tested and am considering for the processing.

 1.      First generating a square wave in phase with the sine wave.

 2.      Generating a triangle/ramp in phase with the sine wave.

 3.      The ability to add or subtract a variable amount of the square and ramp waves to the sine wave.

  4.    I did hook up a ring modulator for fun but we probably won't use that in the lab.

 I am not pleased with my attempts at creating a good sounding note from these waveforms. Probably due to my lack of experience modifying the note and not really knowing what a good note has for spectral content. I realize good is a personal preference. I am assuming that popular Theremins have good notes for now.

 I am soon going to test:

 1.      Asymmetrical clipping or limiting (hard or soft) of the note.

 2.      Anything else someone recommends or knows works for existing Theremins.

 Here is my request. Information that will help me generate good notes. This can be existing analog processing techniques in general or specifically that others use and useful links to Theremin sounds.

 All of the Theremin course is available to anyone. I am always interested in critical feedback of the lab. It will be changed for next semester but not too much.

 Go here and login as a guest.

 https://ay15-16.moodle.wisc.edu/prod/local/wiscservices/login/index.php

 Find ECE370 from spring 2016 for my first attempt at an electronic lab based on the Theremin.

Hello Mark,

The sweet sound…. Often over the years I would bring this subject up and most people would tell me it comes from the way the theremin is played. Ten years ago on one of my scratch vacuum tube theremin designs I found my sound, I called it “Finding Clara’s Voice” which was lost due to time and Robert Moog did try to revive it for her.

Then there were the engineers that swore by using the JFET because they work tube like, took me a week on the bench to tell that direction was not for me so I settled with the NPN transistors. JFET's wiggle like a vacuum tube but they in no way are a tube. lol

On March 2, I started a TW thread hoping to find wise input from others. A couple of years ago dewster shared knowledge and the clouds parted, all my research had been done without looking at what anyone else had done. Later I would hear a voice. (if you build it... kidding)

In the week of Clara’s last birthday I heard “It is Time”. The Link

Weed your way through my madness and I think you will find what you are looking for.

I think designing a cost effective volume control PCB would be good and then there is the issue of interesting enclosure.

Christopher

Thanks oldtemecula, Christopher for the quick reply. The students in the ece department are required to take this course. So every electrical engineer that graduates form UW Madison ECE Department will take it. That is around 50 to 70 per semester depending on whether it is spring or fall.  The design will be analog because that is the lab directive.  It is advanced circuits (Analog). I am certainly interested in what you have done. In line with your modular ideas, I had this grandiose idea that my pcb's would be modular and students would choose what they wanted for each process. Alas I now believe that is asking too much for undergrad students to do in one semester so I give them the design they have to use. However I am going to have a add-on sound processor board for the version of the Fall 2016 semester.

Is your "madness" circuitry available for viewing? Sorry I haven't read all the posts on the forum yet. I am not in the school of it isn't good unless I designed it.  I do give credit for all the circuits I use in the lab. I have added some of my own out of perhaps naivety. For the mixer I use a linear tech part designed for power monitoring and not mixing. It works great and is cheap which means a lot when it is from lineartech. I agree with you about FETs.  I used a few of them in version 1. I have decided to go to bipolar transistors due to the quadratic nature of the FET and the distortion that comes from this. Enough for now. Perhaps I put this post in the wrong group. Do you have a comment on that. I am interested in circuitry but also in pursuit of the sweet note.

Oh yeah google had the Theremin app when you logged in on Clara's birthday. I put a link to the app on the lab website.

Mark said: "Is your "madness" circuitry available for viewing? 

I am going to give you the "Holy Grail" which I had to shed my blood and now you want me to do your homework?  (-'

All posts show up in this link which everyone views, yours is in a good place.

http://thereminworld.com/forums/recent

Christopher

This was published in technical theory. I understand the holy grail. I will post or make public anything I am allowed to publish.  I do not want to publish what is considered trade secrets. As poor as I think they are I will record something. By the way I am very new to the Theremin and I cannot play one yet.

Mark

For me the Holy Grail is mystical and mythical, something the theremin classic purest had only hope to find by spending $1000's only to be disappointed. Ten years ago it was given to me and very few said they liked it. It dwells in a place outside of computer modeling so few were interested in working outside their modeling box and explore why the sound of Lev Sergeyevich develops.

I got old and now my theremin enthusiasm has quieted. I had shown hundreds how to build my theremin design over the years but the Grail was held back until Clara's last birthday. The idea of showing one more person (you) who could teach it to many has me interested.

I think modeling is a good tool to learn with but I think it would limit discovery in using the limitations of previous knowledge. To move forward I myself firmly believe in serendipitous exploration.

Christopher

Edit: With a theremin it is a sin to break from tradition in the classic design and operation of the antenna's, or no Master Thereminist would ever come near it or play it and newbies would have wasted their time learning from it. It takes years to perfect the playing skills so it needs to have a consistent format. A friend of mine designed his version of a theremin, used it in an original Beach Boys song only to be shamed the next 50 years instead of being praise for his accomplishment. Just a heads up if you are in the design stage.

hi mark, there's no sleep around and my input is of no technical help at all. tinkerer/musician here. there is a lot to read and to look at in these documents. thanks for that. looks impressive, that final instrument, which every participant of your course has finally in his hands.  about 50 prsons each year is a lot to me but what's the point if it's not good? or awful sounding? it will end in a drawer and that was that. or they'll have the wrong impression of it. i like the harrison look and the reversed volume of your design. meanwhile i prefer the normal way to control pitch, and volume too, sometimes. i don't know much how all that waveform/brightness works on different models, but it's good to have. i don't even know what your instrument sounds like so how could one tell what you're after. any soundfiles?

keep that good work going on, your in the right forum

I recorded a 40 Hz and 460 Hz note. I put the wav files on the course website near the top in the folder Theremin Rev 1 Audio Samples Folder.

There are time and spectral information along with the sound files. Once again go to the course website.

https://ay15-16.moodle.wisc.edu/prod/local/wiscservices/login/index.php

Then drill down to the course number ECE370 in the Electrical and Computer Engineering site.

I can put the wav files here if that is an acceptable practice and you don't feel like finding them on the Wisc.edu website.

xtheremin8 I completely agree that I should at least do no harm. The students this first time I ran the course ranged from not knowing what a Theremin is to having a well defined idea in their minds what they wanted it to sound like. Students across the whole spectrum were very pleased with what they were able to accomplish in the course.

Hello Mark,

I studied your 460 Hz, besides power supply switching noise it is a nice sine wave which as you know is mostly void of harmonics.

If I had to navigate your webpage everyday I would quit school.

I gave you a link up above to check out. That is what I mean by doing your homework.

My sound byte below starts out like a modern day theremin sound and then I switch in my simple Harmonic Exciter circuit (Holy Grail), in real time, so a bit scratchy until it settles down.

Switched on Clara .wav  (returning to natural analog)

Christopher

It is all madness, technology can be so dry I try to give it humor (-:

I think i would look out for a much simpler mixer, would replace the lp-filter with a single cap and omit the pitch processor completely. Pre-mixer waveshaping then might result in a more organic kind of timbre.

If you want to introduce quite a range of little circuits to your students, a self contained ribbon controller synth might be an idea (just in case a stripped down theremin circuit becomes too boring ;)