I recently got an Etherwave theremin kit, and assembled it with no problems. I managed to calibrate the pitch antenna, but I’m having some difficulty with the volume. I get almost no volume control. No matter how I adjust the inductor slug, the volume seems to go from full on to off, as I move my hand toward the antenna. Has anyone had this problem, and know of a solution?
Thanks,
Frank
If I understand well (sorry, I’m French and German native speaker and my English is very reduced) your problem seems to be that the volume change when approaching your hand to the volume antenna is too abrupt? The “normal” behavior of a well tuned Etherwave is as follows (assuming that the volume knob is in its mid position)
a) older production runs with “normal” slugs: No volume when the hand is at 1cm (1/2") above the volume loop and max volume when at 15cm (6") above.
b) newer production runs with “hexagonal” slugs: No volume when the hand is at 4cm (1 1/2") above the volume loop and max volume when at 17.5cm (7") above.
Turning the volume knob clockwise should “shorten” the volume field, so that max volume is reached at lesser hand elevation while turning the volume knob counterclockwise will “lengthen” the volume field so that you need to lift your left hand more in order to obtain max volume.
The smoothness of the transition between min and max volume depends on the relationship between two resonant circuits: The one is formed by the antenna-hand capacitance and the three large big coils on the left side of the circuit board, and the other by a capacitor, a fixed inductance and a variable inductance (slug) on the circuit board. Since the resonant frequency of the antenna circuit may only be changed by approaching your hand and there is no other possibility to tune it, all adjustments are made on the other resonant circuit, coarse with the slug and fine with the volume knob. If you can’t find an optimal working point with this, it is possible that the antenna circuit is too much out of tune because of parasitic capacitance. Make sure that your Etherwave is not lying on a metal workbench but set up free in the middle of the room on a microphone stand, far away from all metal parts and unneeded cables before you start tuning it.Then observe during tuning if turning the slug L11 and/or the volume knob changes something at all: Does the point where there is no volume go up and down? Does the point of max volume move somewhat during tuning? Let us know this and we’ll do our best to diagnose the problem.
Thank you for the information, Thierry. I appreciate it. Sorry it took so long to get back to you.
I think the problem may be the parasitics, due to the proximity to other objects in the room. It is on a mic stand, but my little studio is rather tightly packed. Can’t really get it out in the open very much. I had to move some of my equipment (keyboards and guitars) out of the room, for some repair work in the room. I took the opportunity to try again, with all that extra space. The volume tuned fine. When the equipment was in the room, there was no real volume change when tuning the slug - nothing to full volume, to nothing again. Now I have a rise and fall of volume during tuning, and good volume control with the antenna. The slug is near the top of it’s travel, but it works.
That brings up a question; will this be a problem again, when I bring the equipment back into the room? I can keep the antennas a couple feet from things, but that’s about it. I guess I’ll find out soon. I can’t tell my wife we need a bigger house, because she’ll just agree with me. ;o)
Thanks again,
Frank
Hmmm, that’s why I’m renting an old house here in France. It has two floors, each one has 160 square meters (should be about 1500 square feet). I’m only paying for the first floor since the second floor hadn’t been used for forty years before we moved in and it was in a terrible state. So I renovated one of the upper rooms which has about 24 square meters (~220 square feet). It serves me now as my theremin room where I practice and do theremin maintenance and repair for others. There is almost nothing in this room, just a small workbench with an oscilloscope, a frequency counter and a soldering iron and at the center of the room my theremin with an amplifier. These are optimal conditions for working and for playing.
But don’t tell this to your wife… 