Thanks Jason, for adding my H1 schematics etc to TW's collection!
But I need to protest at the title! - Not because I have any pretentions about "digital" being "inferior" or the like - If I could build a digital theremin which sounded as good as the H1, I would be well pleased.
The reason for my "protest" is that the Skywave H1 was/is, in the truest sense, a hybrid of analogue and "Mixed Signal" pitch-only theremin..
The H1 had LC Oscillators driving into a MC1496 Analogue 4 quadrant multiplier, the output of which went to the audio mixer - Not a "digital" entity anywhere in the whole signal path!
Then there was a Mixed signal (wrongly, IMO, referred to as "digital" by many - "Digital" IMO means "number crunching" and not simply logic-level.. And I know, in the past I have made this astronomical mistake) "heterodyner" (not an XOR, but a D-Latch) which produced a square wave, and a divider to give a "sub octave" square wave - and these were mixed to taste in the audio mixer.
Effectively, one could accurately say that the H1 combined a fully analogue heterodyning theremin with a seperate mixed signal theremin - but even this is not precise, as both shared the same (LC) oscillators.. The two analogue LC oscillator signals are mixed (heterodyned) in a standard analogue way producing a completely analogue audio difference frequency, and, seperately, these same oscillators are squared and 'heterodyned' using logic, to provide seperate "mixed signal"audio which is mixed, to taste, with the conventional "analogue" audio.
Only the "Wrong-side of null point" indicator and muting was truly digital, and consisted of comparing the frequencies from the reference and variable oscillators, and outputting a high logic state when the variable frequency exceeded the reference frequency, and this digital aspect of the instrument does not affect the signal path at all, except to mute the audio when the thereminist moves away from the instrument.
I feel that we need to be clearer about how we catogorise theremin technologies, or we will start to create great confusion..
Truly digital theremins are only just starting to appear - Dewster is developing a truly digital theremin, and some other truly digital theremins are appearing on the market..
Most "digital" theremins (The "Glasgow" Digital theremin for example) are not "digital" at all - in the main, they are called "digital" because they use logic gates as oscillators and/or mixers - But these are "mixed signal" because they do not "crunch" numbers - they do not use the logic to perform binary computation, and their mode of operation is essentially analogue but uses signals of fixed shape and amplitude (logic level pulses) to produce the analogue output waveform.. It is a bit like saying the Mini Moog was digital because it had a keyboard which output binary states (on of off) and that only resistive keyboards which respond to pressure are analogue.
The Glasgow digital theremin is a sub-group of its own - using logic gates for oscillators and using the difference frequency to produce a voltage which drives a VCO.. It does not actually use heterodyning of any kind to produce the actual audio output.
At the end of the day, for a thereminist, the technology should be unimportant - as long as the theremin performs as they want..
And this is what bothers me - Standard logic gate RC oscillators are inferior to LC oscillators, and "digital theremin" has sadly now been equated to nasty cheap theremins which are unplayable and sound horrible, because they are equated to anything using RC logic gate oscillators! - most of these type of oscillator are unsuitable for use in theremins due to their nonlinearity.
"real" Digital theremins designed for high performance will probably use good LC oscillators at the front end, in order to obtain maximum stability and SNR on which to perform the computations required.
Digital theremins, like Dewsters project, have the potential to be good musical instruments meeting all the requirements thereminists want, as do mixed signal theremins (as proven by the E-Pro).
But, at this time, Digital theremins have not yet "come of age" - and the theremins which are being labelled "digital theremins" are usually awful, and the reason for this is not, or may not be because they are "digital", it is because most of them are just cheap sh*t using cheap logic gate RC oscillators.
Fred.
