DIY power supply for etherwave.

the discussions here: is there a better power supply for an etherwave?  and:  etherwave maximum input voltage gave me the impulse to build one with ground-lift switch. swiss power units are not grounded, so playing through a ungrounded amp, or just with headphones is not possible. i finally clutched all parts together and set the theremin with the new power unit to a small battery amp. (what's more ungrounded than that?) with lifted ground it's useless. but as soon as the ground is switched on, it works perfectly. jippy! and if i should get a groundloop, i'll still have a switch!

i used a new transformer, output with two coils in series, notice the small bridge. output is 15V 300mA. that was the closest one i could get. the etherwave internal voltage regulators don't get hot, so i think it's fine. but i thought about replacing the bridge with a resistor to reduce the voltage towards 14v. 

Hey Dani,

Great illustration, you sketched that?

Just Opinions: If I were to perform in an environment that I found out previously there is no available earth ground I would walk away. From my vacuum tube theremin days and the quest for the classic theremin sound I found distortion in the RF wave shape if I tried to isolate the 100-vdc oscillators using 1-uf 250-volt capacitors. At 922 kHz the capacitor would add less than 1-ohm impedance to ground but the distortion was detectable. A good direct ground does not have this issue.

The sound develops from the RF, mixing and audio enhancement. I have my standard in what is correct and authentic.

Rather than use a resistor to drop the transformer voltage I would use two power diodes in parallel but opposite directions which would drop the AC voltage .65 volts, if needed add another set. Do this outside the box as that is where you want to dissipate any heat. 

On the volume loop I always feed high voltage insulated wire through the tube. Static discharge is about 10 to 15kv so use something rated at/or above 20kv.

With my “Switched on Clara” project I will have photos of the odd stuff laid out before assembly.

Christopher

yes christopher, that's about the way i sketch stuff sometimes. mostly more haywired. but i cleaned and combed and labeled that one a bit for it's public use. to me it makes perfect sense, but does it make sense? i'm looking forward  to a photo serie of your odd stuff.

yes, if there's no ground at all, you better run, if you can. but that's really rare, i hope, to have no grounded power sockets. the cool thing now is, that i can practice with headphones and no extra cable, mixer etc for providing ground anymore.

it's all in small plastic box with cut outs for switch etc. and the main power connection is a common C13 type. the outgoing cable is secured with a zip tie and some glue. the rest of the parts: one switch, one power socket type C14, ~2m shielded or 3wired cable, a midi-din plug, some shrinking tube, some wire and a bloody transformer. costs: all new about 15-20€.

warning: i believe the reader is aware of the danger of electricketry, and takes the necessary precautions by himself. by reading so far you've automatically agreed not to  sue me in anyway.

Very nice sketch xtheremin8!

Just thinking out loud, not recommending anyone actually do this, but here in the US the ground actually does come in through a two prong AC plug, and if it is phased (one of the prongs is wider than the other so there is only one way to plug it in the wall) then the white wire is ground and the black wire is live.  The explicit ground wire in a three prong AC plug is physically connected to the white wire back at the breaker panel.

I wonder if one could use a small capacitor here (~100pF) with a decent voltage rating (~250V) and connect Theremin ground circuitry to the AC ground this way?  That is to say, if there is no better ground available?  Could be a shock hazard though.

Also, I'm a bit confused about resistors before regulators - are we talking series or parallel?  Parallel ones are they're generally there to lower unregulated peak voltage a bit and to maybe bleed things down a bit faster when the AC is disconnected, but if you don't need one for these reasons I can't think of any good reason to include it as it's a power vampire.  Series I would avoid altogether.

dewster, please think out loud, that's absolutely fine by me. i can delete the whole thing, if it may cause serious harm to persons or equipement, without hesitation. no problemo.

i never saw a us-etherwave power-brick from the inside. wish i could. but i opened mine and if you cut out that grounding and that switch in my picture, you'll get basically the same simple transformer that comes with a etherewave. i see, there are major differences in the power lines between different countries. here we have: null(brown or black), phase(blue) and ground(yellow green striped) cables.  ground is usually clamped to the incoming water pipe somewhere in the cellar. i think that's european standard? 

i'll check the chef from the electro-shop, he smells the bullshit from miles and tells me straight away.

xtheremin8, sorry I wasn't clearer, I wasn't criticizing anything technical in your most excellent drawing.  Ground lift to kill ground loops makes a lot of sense, most guitar amps have this.

I was just sort of floating another possible way around the lack of grounding issue and didn't want people to think I was endorsing it.  Here in the US two prong AC phasing is a rather recent thing, so one can't count on it to deliver hot and ground correctly.  Three prong with explicit ground should always be safe.

thanks, you are all too kind. it's all a bit a learning thing here, so i appreciate your inputs very much.  the principal: as long as it sound good and does not smoke, why worry? is a bit taken too casual by me. fact: the whole idea came up by that ground lift switch i've seen on guitar amps and those groundless issues i stumbled into last year.

yes to reveal wich line is phase i usualy use a so called phase-tester. looks like a screwdriver with a light bulp in it and a contact on it. it lights up when you found the hot wire on the power socket, lamp etc. a very usefull tool.

that the prongs are different in america needed a closer look.  here you never can be sure, which one is which, as valery said. you're right valery, the removing of those two pins is absolutely not necessary.

and don't forget to switch the power-brick off when not in use.

so i went to the electro-shop the other day and had a little chat with the chef about that ground-lift device, it's possible danger etc. and luckily he knows what a theremin is. to my own relief: there is no danger, if it's phase, null and ground on separated wires! the method of ground on null, as dewster explained, was here used too, and still around in many older houses. my most weirdest experience was some years ago, when one of two main fuses was blown, so there was still light but no stove. if i turned the stove on/off the light in the bathroom went also on/off. i did not shower that day...