@dewster: It's making enough money to support a big family?  Wow, I'd figured that it was the niche of all niche markets and you'd be lucky to sell ten or so in as many years.

For the Newbie: We have been in the sweat lodge for the last few days straight, not even allowed to go pee.  Time to air out some laundry and lighten this thread up.

I am about to step in it, because I have been holding it, hopefully those that read this thread are having as much fun as me. Of the 3 wheel spokes spinning this thread I should not be here as I mentioned before I am not a musician and never worked in electronics. This gives me a type of freedom to explore and an excuse when I approach nonsense.

Timbre a word I had never heard before landing on planet TW...had to look it up actually and still not quite sure.

Here is a non-hack EWS $5 timbre fix that is so simple you could go to Radio Shack and have it working tonight. Take the sharpness out of your theremin tone plus add two lower octaves.

To all young electronic builders, if only a few still exist, put on your list for Christmas a two channel 25 MHz or higher Oscilloscope. With that you can see sound or theremin EM fields. They will talk to you with wave shapes. Add in freeware to measure harmonic content and you will see the relationship between wave shape and timbre. The sound of Clara Rockmore’s theremin is the fundamental audio freq, 50% second harmonic and 25% forth harmonic (no third harmonic) and then add in her grace. (There is one more feature but I will let you discover that.)

Add in the third harmonic and you get that baritone tuba sound. Approach a sine wave you get that whistle some people like.

The Timbre circuit can be very simple in design. My tube/valve theremin just uses a short piece of open ended wire feeding a single glass diode. Both pitch oscillators fill the air with radio waves (some think otherwise) so I take advantage of this with a crystal radio configuration like you made in middle school. Want a different timbre move the wire. This protects the solid state from high voltage plus it blocks any weak background noise like electrical spikes or radio stations. The engineers would call this a signal to noise ratio or just unacceptable.

My Tube/Valve.mp3  180k - All the buzz and sass of Clara Rockmore captured on a loose wire floating in the ether. This is the theremin to sound card direct, so no acoustic development.

I once posted at TW the 13 myths of theremin design and that list was serious, as I believe there are those that use misinformation to conceal the theremin in mystery.

Once again that is not a bad thing; it kind of makes us all special when we find the truth.

As they say the Chimp is 95% human, the theremin is 95% Tesla Coil.

Christopher

@Thierry: "Naturally not. That isn't the intention. I just spoke about paying back the money which I invested."

You had me going there.  I was afraid there were four children in France roasting sparrows on a hanger under an overpass because I posted a pencil-drawn schematic on an obscure corner of the internet. :)

@RS Theremin: "To all young electronic builders, if only a few still exist, put on your list for Christmas a two channel 25 MHz or higher Oscilloscope."

If I were in the scope market right now I'd probably get either a Rigol DS1000E (2ch, 100MHz, $400) or DS1052E (2ch, 50MHz, $329).  I haven't used one, but they have persistence (infinite is nice for checking oscillator drift), deep sample memory, a bunch of auto measurements that look handy, FFT, and USB connectivity.

Thanks Dewster for all your experimenting and posting! When time permits I'll give it a try.

Had you done any buffer experimenting using FETs?

"Had you done any buffer experimenting using FETs?"

No.  With the stock mixer loading (caps to a grounded diode) I figured caps to BJT emitter followers probably weren't a big deal.

Hi Dewster,

Yes - I would be interested in seeing it! I am slowly getting back to normal (whatever that is, LOL) and looking at the ideas of others is always educational..

I am personally biased (probably irrationally) against digital theremin implementations - but there is an extremely grey area IMO with regards to how one defines "digital".. I will elaborate a bit..

IMO, use of logic levels does not make something "digital" - Using CMOS oscillators and mixing these with an XOR does not, IMO, produce a digital theremin, it produces a mixed signal theremin.. my reasoning is this - if the VFO tracks the capacitance WITHOUT any quantizing (as in, the frequency changes are analogue, complete with distortion of the waveforms [logic level square wave] period as a result of the changes in frequency, then the output (difference) waveform will carry this (pleasant) distortion - IMO, it is the change in harmonics which occur as frequency changes, which contributes most to the analogue (and mixed signal) theremins distinctive appeal.. This IMO is also the main reason why analogue synthesisers sound different (better IMO) than digital synthesisers when portamento or pitch bending is applied.

Mixed-signal theremins lose the added harmonics which result from changes to the oscillator waveshapes (as in, amplitude or 'Y'changes as opposed to time/period or 'X' changes)  - but, IMO, these are not really of any major significance until the oscillators start to pull on each other (down at the bass end) - IMO, the major harmonic contribution is that provided when pitches are changing (as in, "distortion" of the period or 'X' axis) , and these are retained in a mixed-signal design.. An XOR (after minimum filtering to remove sum components) will produce a triangle wave of the difference frequency of frequencies applied as two square waves to its inputs, but while one input frequency is changing, this triangle wave will undergo distortion (changes to the mark/space ratio of either input square wave will also distort the waveform, and this can be deliberately trimmed to obtain different waveshapes)

"Digital" IMO, is when (a) the audio frequency is computed from a quantized capacitance - effectively, if one converts the incoming capacitance change into a digital quantity, one gets "steps" of frequency changes.. Now, I know that with large enough resolution, these "steps" may not be at all audible.. And I know that, at some point, these steps will be lost for all practical purposes (they will, in effect, have the same significance as the noise inherent in all designs) - But, well - I am not convinced that we have reached that stage yet...

(b) Once the audio frequency is computed, the output waveform can be constructed and output - and here, I think, is the major difference between analogue / mixed-signal and Digital.. I may be wrong, but if the output is changed on a per-cycle (as in, audio period) basis, the waveform distortion which occurs naturally in analogue / mixed-signal designs would be eliminated - there would be a series of audio cycles 'clipped' together.

But - I may be out of touch.. The last CPLD's I worked with were the Lattice Mach 4's - And most of my expierience was with GAL16V8's.

One thing you say really worries me: "and feel I'm following in your footsteps (and Bob M.'s - and I say that with the greatest humility) to some degree"

Beware! This is a dangerous path! I am half dead, completely broke, and about to be divorced - and I can put at least 50% of the blame for these on the day I first decided to design a better theremin!

My email is in my picture - but in case you cannot see it... fred at fundes dot co dot uk.

Fred.

"Digital" IMO, is when (a) the audio frequency is computed from a quantized capacitance - effectively, if one converts the incoming capacitance change into a digital quantity, one gets "steps" of frequency changes.. Now, I know that with large enough resolution, these "steps" may not be at all audible.. And I know that, at some point, these steps will be lost for all practical purposes (they will, in effect, have the same significance as the noise inherent in all designs) - But, well - I am not convinced that we have reached that stage yet...

Yes, there is definitely quatization going on, but the steps can be made small enough not to matter with sufficient SNR from the AFE and some low pass filtering.  I analyzed this on and off for a month or more just to make sure it was theoretically feasible.  Any resolution is possible if the low pass filter can be set low enough, but response time suffers if it is set too low, so there is a tradeoff.  I'm hearing some pitch quantization in the lowest (mostly subsonic) registers, but I haven't finished tweaking the DPLL and LPF parameters yet.  Also, the LPF is a simple first order, going to a second order should give much better SNR.

(b) Once the audio frequency is computed, the output waveform can be constructed and output - and here, I think, is the major difference between analogue / mixed-signal and Digital.. I may be wrong, but if the output is changed on a per-cycle (as in, audio period) basis, the waveform distortion which occurs naturally in analogue / mixed-signal designs would be eliminated - there would be a series of audio cycles 'clipped' together.

The waveform could be changed on a per-sampling clock period or even faster (the beauty of doing this in logic rather than software).

Beware! This is a dangerous path! I am half dead, completely broke, and about to be divorced - and I can put at least 50% of the blame for these on the day I first decided to design a better theremin!

Oh Fred, you have my sincere condolences.  I must say reading your posts on Theremin development has been fascinating, though something of a cautionary tale, for me (but more from a technical angle as I have little knowledge of your personal life).  Having an understanding (or no) spouse seems to be job 1 when it comes to getting anything concrete done in life.  I'm very lucky that mine more than tolerates (at least for the past few years) my flights of fancy in my semi-retirement.  She's a music major and private piano teacher so she pretty much gets that side of it.  Now if my health just holds for a while and the money doesn't run out...  The healthcare industry in the US seems specifically designed to put even relatively healthy people in the poor house.

I am replying on the "Lets design and build a mostly digital theremin" thread.

I am not an electronics expert so I don't fully understand everything I read on here.   I do know that I purchased the EWS from Dewster with the YAEWSBM installed as an inexpensive back up to my recently acquired EW Pro. The EW Pro has been in it's gig bag ever since!  I love the linearity and sound of the theremin... it is truly a pleasure to play. 

It amazes me that a tiny module the size of a large postage stamp can transform the EWS into such an amazing sounding instrument.  Thanks to Thierry's ESPE01 and Dewster's YAEWSBM Moog should be embarrassed and ashamed for not making these improvements themselves.  They have done nothing since the termination of the EW Pro to appease those of us who are more serious about playing the theremin than using it as sound effects in a suburban garage band!

My hat goes off to everyone on here who contributes to making the theremin a better instrument for all of us....especially those of us who are electronically challenged.  I truly appreciate this website!