Cleaning Up The Power Supply

I was reading a recent levnet issue in which power in a venue was very ratty, and causing the pitch, and volume fields to change.

I wonder what would happen if you put an uninteruptable power supply between the theremin, and the house current? These devices are designed to clean up the power so computers don't get damaged. Wouldn't this work for theremins?

Some uninterruptable power supplies condition the power coming in to ensure that whatever is plugged in gets smooth, stable power, and if the power is too unstable (even if it's still on) they'll switch to battery for a little while until it calms down. Others don't condition the power and will only switch to battery if the power goes out.

All of them that I've seen, when they switch to battery they emit a really loud BEEP that you don't want during your theremin performance. It's designed so the system administrator in the next room can hear that something is wrong so they can come turn the server off, or so the idiot who just kicked the UPS's power cord out of the wall can fix it.

So, make sure it conditions the power supply, and snip that little alert speaker.

And remember that opening up a UPS is really dangerous because it contains wall power voltage inside even when it's unplugged and turned off.

Living in brown out central, at the very least I always use an APC SurgeArrest surge protector.

Decent power conditioners, even without the fail over power supply you mention, seem to get much more expensive. The ones I've seen are hefty to carry around too.

I'd think fail over power would not be that useful, if the house power goes, keeping power to the theremin may be your last concern.

Has anyone here found a high quality power conditioner that's at or under US$ 500 and easy to carry?
Has it helped?

Please excuse my bad English (normally I speak French and German), but:

The output waveform of such UPS is often far from beeing a pure sine wave, so there is a risk of new "side-effects" on your Theremin.

Since most Theremins operate with low voltage, I think it makes more effect to stabilize their power supply on the secondary site, to get a stable output voltage without variations and transient peaks.

An electronic-regulated power supply gives normally a stable output voltage, but does not take care of the RF sensibility of our instruments. So an additional low-pass-filter just between the DC conductors and the printed circuit board could decrease negative effects.

If you are interested, I'll be happy to bring my knowledge in here.

We are very interested in whatever you have to offer in this matter. Thanks.

OK, I'll start with "googling" for schematics of the different Theremin models and brands. After studying them, I'll come back with my ideas.

Update: I found the schematics of the Paia Ethermax, Art Harrisons 145 and Moog Etherwave Standard. Their power supplys are all very different, so I will have to develop individual strategies. In two weeks, when my B3 will arrive, I will see if a fourth strategy is necessary.

The Furman power conditioners take care of all the sorts of problems you could encounter (low line, high line, RF interfence), but do cost a lot!