These are the differences between the B3s and the Moog Etherwave Standards.
B3 original (small one) B3 Deluxe, and B3 Pro all use the same non-removable thick wire type volume loop, and telescoping (multi-segment) antennas, as well as the same circuitry as each other. (all 3 sound alike).
B3 Original comes in short plastic cabinet with externally attached mic stand mount. (remove for table top playing. )
B3 Deluxe comes in 18 inch long wood cabinet painted black with textured paint. Recessed mic stand hole
B3 Pro comes in more fine detailed 18 inch wood grain / stained cabinet, available in wallnut, cherry, and sometimes tiger mapple, and features a touch plate mute switch with LED power / mute status indicator. Recessed mic stand hole.
All 3 models only have pitch and volume knobs. There are no controls for tonal charactor. However, the B3s sound like a soft cello in the low notes, and gradually change to a more gentle female vocal tone in the upper notes.
The B3s are excelent for classical works because of their soft, string / vocal charactor.
These are simple theremins, but I prefer them as student instruments as there's nothing to distract you from learning your techniques.
The B3s use 2 prong wall-warts.
The B3s just slip on to a mic stand. No spinning.
All B3s warm up in less than a couple of minutes.
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The Moog Music Etherwave Standards come in a larger wood cabinet, are heavier, and use larger diameter (3/8 in) nickle plated brass tubes for the removable volume loop and pitch rod which thread on to the instrument.
The EW Std also features a built on threaded mic stand mount which requires that the instrument be spun on to a mic stand. They have feet which allow for table top use.
The EW Std has in addition to the pitch / vol sense knobs, two controls for tonal charactor. Namely, wave-form, and brightness.
The sound of the EW Std is more of a bright, and loud brass instrument. I use the EW STD for jazz, and blues.
The EW Stds also feature power cords which use 3 prong grounded wall-warts.
As of this past month, Etherwave Standards are now available with CV outputs, power LED, Pitch Preview, and more. Upgrade kits are now available for existing EW STDs.
Etherwaves take between 10 and 20 minutes to fully warm up depending on conditions.
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These two makes of instruments are not about getting what you pay for, it's about which one is right for the kind of music you perform, and where you're at in your development with the theremin.
I hope this helps.