Basics of how the EW-Pro works.

[i]"just as a fan of high performance cars would view a Lamborghini fitted with an engine designed by Škoda Auto with some cynicism." - Gordon[/i]

To me, the analogy is more like a Lamborghini fitted with a lawnmower engine.. The space (and cost) saving allowing brilliant extra features to be fitted under the bonnet..

The astounding thing is that Bob Moog managed to engineer the "Lamborghini" in a way that allowed discerning drivers of the vehicle to be unaware that it was being powered by a lawnmower!

It is interesting that Bob took that route with the E-Pro. I wonder how much longer that early series of CMOS will be around. Early experimenters used those 4000 series parts in their analog range for all sorts of things they were not intended for. For that matter, small scale integration of all sorts (TTL, LSTTL, HCMOS, etc) are being forced out by cheap FPGAs not.

Comparing the rock-solid oscillators and the sophisticated linearization circuits comprising not only "classical linearization coils" hidden in the pitch arm, but also dynamic coupling of the oscillators, to a lawnmower engine is IMHO not justified. The engine of the EPro is a Lamborghini engine. But its power is limited afterwards in order to fit into a Skoda gearbox.

[i]"It is interesting that Bob took that route with the E-Pro. I wonder how much longer that early series of CMOS will be around. Early experimenters used those 4000 series parts in their analog range for all sorts of things they were not intended for. For that matter, small scale integration of all sorts (TTL, LSTTL, HCMOS, etc) are being forced out by cheap FPGAs not." - Don [/i]

Standard 4000 series, HC, and HCT CMOS families are likely to be manufactured for the forseeable future - most (if not all) have gone through the upgrading process to meet RoHS compliance, they are still profitable, and I have been advised not to worry about availability of common parts (I was worried about the 4046 - but was advised that, at present, the 4046 and HC4046 are not scheduled for discontinuation). I have been advised that the first common sub-family likely to dissapear is the HCT family, as its compatibility with TTL levels is not a common requirement these days... But, like all these issues, one gets different stories depending on who you consult.

I am extremely surprised that Moog did not put all the logic into a cheap CPLD - A single Lattice MACH part costing less than $10 could have easily taken the lot, reduced the board size, made manufacture and testing easier.. and hidden the way it operated.. I know this because I have put all the logic required to implement the range switching (dividers and selection logic etc, and XOR) and a D-Latch to implement my square-wave digital heterodyning, and a of switched capacitor filter, and all the logic and most of the analogue to implement my volume circuitry, and PWM output to generate volume control voltage... All this, on one low cost (<$20) PSoC part.

Now - in case this leads you to believe that I was intending to clone an E-Pro, let me assure you this was not the case... I did all the above before I knew the E-Pro secret! It just happened that the elements I required for control of my analogue Theremin were an almost exact replica of the digital stuff which makes the sound source for the EW-Pro!

In fact, you can glean what my direction is if you read prior posting regarding frequency multiplication, and the heterodyning VCO..

All that work just because I could not accept (would not even look at) the idea of a digital sound source! - However, I still think my results will be better. ;-)

[i]"Comparing the rock-solid oscillators and the sophisticated linearization circuits comprising not only "classical linearization coils" hidden in the pitch arm, but also dynamic coupling of the oscillators, to a lawnmower engine is IMHO not justified. The engine of the EPro is a Lamborghini engine. But its power is limited afterwards in order to fit into a Skoda gearbox" - Thierry [/i]

LOL! - You are right Thierry..
It is the "Gearbox" which "limits" this Lamborghini.. When I was talking about "engine" it was with reference to the sound generation only - the "sound engine" - I was not in any way intending to slight the front end gestural control interface.. As with all analogies of this kind, one can only carry them so far before they become silly! In the case of the E-Pro, the sound generating and range switching (engine and gearbox) are effectively one and the same unit - once the oscillator signals have been digitized, then the "engine" thereafter is digital - And as the function of the oscillators is therefore one more of providing the source from which the engine operates, one could regard the variable oscillator as the fuel pump and the reference oscillator as the air intake / carburetor..(or probably the other way round - as the carburetor is what is used to control the flow, just as the variable oscillator is used to control the pitch - but what do I know.. I am an electronics designer not an auto designer - and this analogy is way beyond my abilities now!).

The interesting thing is that the (front end) linearization techniques are similar in principle to how the Tvox equalization works (oscillator coupling - probably the cause of its wonderful tone).. but the E-Pro "gearbox" allows better use to be made of the most linear zone.. Also, in the case of the Tvox, ONLY oscillator coupling is used - with the EW-Pro, both oscillator coupling and antenna equalization are used.

It is sad that the rich harmonic variation which must result from the oscillator coupling in the EW-Pro is all lost as a result of the gearbox.. In a way, what I am doing is putting the gearbox [b]before[/b] a good engine.. but that analogy doesnt really work well..... ;-)

One thing is constant in all theremin/car analogies...


The most likely cause of failure is the nut behind the steering wheel.

There are wine tasting goblets specially made for professional tasters that are hand blown from black onyx glass so that the taster cannot be influenced by color. When listening to the sound of a theremin, we should always use a black onyx glass.

What constitutes "good sound" from a theremin is a matter of personal taste, and preferences vary greatly from person to person. "The theremin", if I may quote Dr. Bob, "is totally at home in the electronic environment" and because of this it invites electronic enhancement and modification of its basic sound. Whatever your theremin lacks in order to be your ideal sounding instrument, you may be able to add with the use of peripherals.

When I play my E'Pro theremin, I put it through devices that cost many times what the instrument itself cost! The casual theremin hobbyist is unlikely to want to spend that kind of money on the sound of his or her theremin. Most of the time people who do use external devices (beyond the requisite amp/speaker) use low end equipment designed for guitars. There's nothing wrong with that provided you are getting the results you want.

I sometimes wonder, however, if these people are using equipment because they actually prefer it or if they're using it because it's affordable. Have they really experimented with the full gamut of what's available? On many occasions, I have taken my theremin into a well-stocked music store and plugged it into everything! This is something I have often urged others to do over the years, and I have found that music stores love it. Tell the manager of the store what you want to do and ask him when it would be convenient to bring in your instrument. Most people are fascinated with the theremin and are delighted to have the opportunity to see one up close.

The question is not whether your theremin is your ideal instrument. It probably isn't. The question is, are you doing everything you can to make it into your ideal instrument by exploring the incredible range of equipment available to the electronic musician.

What do you get when you take the lawnmower of theremins and put it through the Lamborghini of EQ devices?

A Lawnborghini.

The doors to the Holy of Holies of the E'Pro theremin have been ripped asunder and the contents of the tabernacle have been revealed for Philistine eyes to gaze upon!

Am I the only one who doesn't particularly care that it was empty?

Coalport wrote: "Am I the only one who doesn't care that it was empty?"

Well the inside of the Arc of Covenant (at least the Myth Busters version) is empty too ... just watch out for that huge electric charge gathered between the inner and outer walls. LOL

[i]I sometimes wonder, however, if these people are using equipment because they actually prefer it or if they're using it because it's affordable. Have they really experimented with the full gamut of what's available?[/i]

Well, I can't speak for all budget thereminists, but you can be reassured that there is at least one who spends his money judiciously and does his research. My setup is spartan in the extreme, but I honestly doubt it could fit my requirements signifcantly better without spending a whole lot more - diminishing returns, and all that. 

Sometimes I wonder if people with a surplus of high end gear are really getting the most out of all that fancy kit. But let's continue with the motor car metaphor for a while. My first car was seriously underpowered (a Fiat 127) and sometimes the driver of a very impressive vehicle behind me would become impatient with my progress and turbo his way past me, showing me one of his fingers before vanishing over the horizon. At times like that I would break out my secret weapon and engage my brain, predicting the road ahead and so on until I could potter past him while he sat in a queue. Sometimes I would even show him the same finger he showed me. :-) A fool and his money, eh?

(No! I don't mean Coalport! Just in case anyone thought I did.) 

Actually, Fred, it is useful information to know that the timbre doesn't seem to, or at least doesn't have to come from the products generated in the mixing process.

Have you or anyone else looked at the output of the mixer in various designs with a FFT analyzer? I wonder what the differences in harmonics would be. Since there are lots of harmonics in squarewaves, maybe the mixer output would be richer in harmonics for the CMOS design than an analog one?

What would follow that would be various filters for waveshaping back to something more like "theremin sound".