self powered amp/ speaker for busking with theremin

The one I worked on last year had a 3 prong IEC wall plug going to a Moog branded "rat in the snake" 100V - 240V in / 12V @ 2A out switching supply.  I assume the ground was transferred through that?

Yes, thats right. The AC part is such a 3 prong wall plug, but how is the grounding for the DC 12 V output made? Capacitors to both poles, one pole? Measurements show no connection to the AC plugs, no DC connection to the output. Capacitance (measured with 200 Hz triangular voltage) is fluctuating between 300 - 400 nF at DC minus. After a few seconds charging time about 9µF against DC plus. Unfortunately the power supply cannot be open without destroying it. The supply itself makes ugly RF Flickering, but the theremin seems to ignore it. I do not know how simple or special this works.

"Measurements show no connection to the AC plugs, no DC connection to the output. Capacitance (measured with 200 Hz triangular voltage) is fluctuating between 300 - 400 nF at DC minus. After a few seconds charging time about 9µF against DC plus."  - JPascal

I did an experiment long ago to see if capacitive (AC) grounding was sufficient, and it seemed to be.  IIRC 100 nF or perhaps even smaller worked like DC, so 300 - 400 nF should be fine.  It sort of makes sense that this isn't a DC connection, because that can cause a ground loop if the audio side is also grounded.

There is what appears to be a second switching regulator inside the new EW, I assume to generate -12V.

When my 4th year MIT student was at my house demonstrating his vacuum tube theremin build, it kept tripping the ground fault receptacles he plugged into. After a little thought he said his design was using the neutral side of the outlet for a ground. Oops

I think the theremin should get priority when it comes to setup & earth ground and think ground loop hum should not be an issue if both the theremin and amp are plugged into the same outlet. Also a $14 isolation transformer from Amazon could be added.

Of course a theremin or any oscillator will work without an earth ground. Not everyone is after the full potential & sound of the Theremin Phenomenon or  . . .  even know what it is.

It is what Lev Sergeyevich Termen first discovered, it begins with a fluctuating sound he heard. Proximity control is just a byproduct of the phenomenon.

My theremin journey begins with Paul Tanner ("Good Vibrations") and concludes with MIT student Tanner Packham, this kid is a genius.

Brian Wilson as a kid use to visit Mr. Hoffman’s house and from watching him play the theremin became inspired by it.

Brian almost used a modern day Thereminist we all know so he could set free the theremin myth in a movie.

Here is the authentic Theremin Phenomenon trying to mimic a synth, a few might notice a difference.

Happy Holidays Everyone

Christopher

"When my 4th year MIT student was at my house demonstrating his vacuum tube theremin build, it kept tripping the ground fault receptacles he plugged into. After a little thought he said his design was using the neutral side of the outlet for a ground. Oops"  - oldtemecula

Jesus, get that kid away from electricity.  

Even though AC neutral and ground are (supposedly) connected at the breaker box, ground is a separate wire that (generally) carries no current, so it should be (theoretically) cleaner.

hello zigg,
i only know of one person who busked around with a roland micro bass. check this out: busking
i think there was some discussion about how to ground battery powered gear here on t.w.
hope it might help (of some sort) and welcome to thereminworld.

I saw this guy's setup years ago and copied his design with some modifications.  The Micro Cube Bass Rx works quite well.   I ground mine with a 15 ft. audio cable plugged into the back and coil it on the ground around the case with my feet inside the coil.  I used to have an internal battery but now I power the theremin and the amp with a Talentcell power supply which lasts forever! Here are links to the pics.  Attaching pics to these posts have always been hit and miss for me. WHY?

https://www.dropbox.com/scl/fi/0wtkko3fujtbg47wndu9z/20231124_185055.jpg?rlkey=kzsa4j2pgjlruvpb9fybci5zl&dl=0

https://www.dropbox.com/scl/fi/q70r243z30wspwijqi021/20231124_185107.jpg?rlkey=zsex2nohvbi9vmiu4wrn0n5fe&dl=0

https://www.dropbox.com/scl/fi/dy638p614hav0vo8o97kk/20231124_185126.jpg?rlkey=44ugt07etjtbwhwf7d7000wah&dl=0