Never played with one of these, but I would not buy one! - Reason? .. Well, they talk utter rubbish about 'digital' 'analogue' 'chips'.. and the waveforms they show in their add are completely meaningless.
There is NO useful data - Linearity? Playing range (distance)? Number of octaves? USABLE number of octaves?
See thread "Theremin Pseudo Science"..
As I said, I have never played one of these - But, if they are any good, they sure know how to advertise in a way which puts off anyone with any technical knowledge.
The PCB looks minimalist - perhaps 4 or 6 transistors, 2 inductors, R's and C's.. Heterodyne mixing will probably be a simple diode mixer, there will be 2 nearly identical LC oscillators.. This is analogue, it does use inductors - BUT - so what.. ? .. I do not see even rudimentary equalisation, or anything which is likely to make this much more than a toy.. BUT I COULD BE WRONG!
It is worth noting that the Etherwave, EW Pro, Midi VOX, and almost every recent respected Theremin use 'Chips' - 'Chips' are NOT a bad thing.. Also, The EW Pro uses LOTS OF CHIPS! - And it even uses (UGH!!) DIGITAL Chips and CMOS Chips.. and even uses CMOS chips in the Audio path!
Also, worth noting - Some expensive and extremely respectable Theremins (one brand in particular) do not have inductors - the oscillators being designed with wein bridge circuits.
If you are used to playing the Etherwave, you are likely to find this maniac's Theremin unplayable.
---- BATTERY SUPPLY FOR EW ---
Perhaps your best bet is to put a battery supply together for your EW..
You need 2 supplies of between 15V and 24V each (4 9V batteries wired in series, to give +/- 18V will do fine) *+18V*---[+9V-]--[+9V-]--*0V*--[+9V-]--[+9V-]--*-18V*
0V goes to the mid pin of the power connector, there are 2 unused pins on this connector to which +18V and -18V can be connected.. Wire the +18V to the Cathode of D2 (the side with a line on it) and -18V to the Anode of D3 (side which is not marked with a line)
Doing this, you could plug either the batteries or the power supply in, to power your EW.
Email me if you want full instructions.