Of course I'm a total newbie but I've studied hard lots of manuals and tutorials before deciding the purchase. I know theremins are VERY sensitive to the surroundings, but what I didn't expect was the mic stand itself to completely mess the tuning.
In detail: when I set up the Etherwave on a wooden table, or even a metal X-stand (much bigger and heavier than the mic stand), everything works as expected: the volume knob actually regulates volume (turning it clockwise increases it, typical use setting around 1-2 o'clock), and the pitch knob fine-tunes pitch sensitivity (zero beat and more or less linear scaling when the knob is around 3 o'clock).
When I mount the theremin on a mic stand (straight single-pole type, with heavy round metal base), the behaviour is totally different. Pitch sensitivity is totally different, meaning not only that I have to turn back the tuning knob at around 12 o'clock, but also that scaling is different and pitch rises sharply when I stand back 1-2 meters from the instrument.
Also, the volume behaviour changes completely: adjusting the volume knob has basically no effect (it actually decreases a bit at maximum settings), I have to set it at minimum value, and instead of a smooth transistion, I hear a small "glitch" just before volume drops to silence.
The instrument is properly grounded, my music room is quite crowded but there are at least 4 feet from any furniture, keyboard or large objects. Just to make sure, I tried it in other rooms with more-less furniture, and the behaviour is the same, so I'm pretty sure it depends on the stand type.
I'm surprised I get these quirks on the mic stand and not on the X-stand, but that's how it is, and I know I will probably have to tune the etherwave.
Which brings me to the second part of my post: I'm a bit perplexed by the procedure. First of all, the manual that was included in my box is not the same as the one you can download from the Moog website. Mine is much more complete, with lots of information, circuit diagrams and the full procedure for building and calibrating the Etherwave (I guess it's the manual of the Kit version). The online manual does NOT include tuning instructions, which is a bit weird.
I couldn't find this version of the manual anywhere in pdf, but the text version is here:
https://translatedby.com/you/moog-ether ... /original/
This is what it says about tuning the pitch:
I'm a bit perplexed by the need to "short" or temporarily solder C28...I have no soldering skill and certainly won't try that on a brand-new instrument. Is it really necessary? All the tuning suggestions I've read make no mention at all of this.Using a clip lead or a temporarily-soldered wire jumper, connect the two leads of C28 together. (C28 is a small capacitor, about 3" to the left of the PITCH ANTENNA connection on the ETHERWAVE circuit board.) Then connect the instrument's audio output to headphones or a monitor amplifier. Now follow these steps to adjust L5 and L6:
Set P1 (the Pitch Tuning control) to its mid-position.
Grasp and hold the pitch antenna with one hand. With the other hand, adjust L6 for zero beat. Note: If the slug in L5 is fully counterclockwise, you have to turn it clockwise a turn or so in order to hear zero beat.) Then carefully turn L6 counterclockwise until you hear a pitch of about 3 kHz (3-1/2 octaves above middle C.
Let go of the pitch antenna. Slowly retract your hand from the vicinity of the antenna. You will hear the pitch go down.
If the pitch does not go down to zero beat when you've retracted your hand completely and stepped back, then L5 is set to too low an inductance. Advance the slug in L5 (that is, turn it clockwise) a small amount - perhaps 1 /10 turn or so - and repeat steps 2 and 3.
If the pitch goes to zero beat and then begins to ascend as you retract your hand, then L5 is set to too high an inductance. Turn the slug in L5 counterclockwise a small amount, and repeat steps 2 and 3.
If the pitch jumps abruptly to a very different pitch as you retract your hand, then L5 is set to far too high an inductance. Turn the slug in L5 counterclockwise perhaps 1/4 turn, and repeat steps 2 and 3.
Eventually you will converge on the proper settings of L5 and L6. The idea is to achieve settings in which the pitch is at zero beat when you've stepped away from the theremin, begins to ascend when your body is about 24" from the pitch antenna, and is about 3 kHz when your hand touches the pitch antenna. Tap lightly on L5 and L6 as you converge on the proper settings, as this will stabilize the tuning slug positions.
Also, this procedure doesn't talk about linearity: will I end up with a more less linear tuning, or is there some other trick required for this?
The tuning of the volume knob seems much simpler:
I hope this makes sense to experienced users, if you have any commment or advice to give me before I embark on opening up my new theremin, all tips&tricks will be VERY welcome!B. Adjusting L11 without a voltmeter:
Remove the temporary shorting connection across C28. Install the volume antenna. Position your ETHERWAVE so that the volume antenna is at least a foot from furniture and other large objects. Follow these steps to adjust L11:
Set the VOLUME knob to its mid position.
Carefully turn the slug in L11 counterclockwise until it is out as far as it will go. Then turn on your amplifier and set its volume control so that the theremin tone will be audible but soft.
Slowly turn the slug clockwise. At some point you will hear the theremin tone. As you turn the slug in L11, the tone will get louder, reach a maximum loudness, and then get softer. Turn the slug back to the maximum loudness, and notice how loud the tone is.
Slowly turn the slug counterclockwise until the tone is about half its maximum loudness. You should then notice that bringing your hand near the volume antenna lowers the volume, and the tone is complete silent when your hand is two or three inches from the volume antenna.
This completes the tuning of the Volume Oscillator. In performance, the exact volume tuning is achieved by adjusting the Volume Tuning control.
Thanks!