self powered amp/ speaker for busking with theremin

Can anyone suggest a suitable battery powered speaker for busking with theremin?  I have been searching and working on this project for year or more with nothing but frustrating failure in my endeavour. At home I run my B3 pro through a talking box (gives a breathy/ human sound) with Hartke 100W keyboard amp. The tone is pure/strong. I am able to power the theremin and talking box with separate battery packs. My last hurdle is a battery/self powered amp/speaker. I have tried all types of battery powered amps but the result is a hideous growl/scratch each time. I have experimented with various noise/interference reducing plugs and boards to no avail. I've tried Roland cube,(have since learned that a theremin will not work with a guitar amp. ) I have since tried Bose, LG. as well as trying to power my entire set-up including my Hartke with a portable  AC power box but no good.  I live in Perth Western Australia,there are no theremin retailer  and I took a chance buying the B3 online, but have been pleased with it. There seems to be no expert in Perth who is able to help me with my frustrating project of being self powered. Does anyone have suggestions?  Could it perhaps be an earthing issue or something like that to do with my B3? I am not an electrical whizz but have researched as much as I can online.  I would be most grateful for ideas/ suggestions. Cheers Thuggboy Zigg.

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.

As my kind Swiss friend xtheremin8 wrote already, the problem is not finding a suitable battery powered amplifier, even a "Ghetto Blaster" will do that job with the theremin connected to its "aux" input, but the problem is grounding. A theremin has to be grounded in the same way as old long wave radio receivers had to. This ist nowadays normally done by connecting the theremin to an amp which is grounded through its 3-prong wall plug. The theremin's power supply itself provides no grounding to prevent other nasty effects like noise and hum induced by so-called ground loops which are created by multiple grounding of the same device chain.

Thus, there is no battery powered amp which will solve your problem, especially not in conjunction with a B3 theremin which is much more sensitive to dirty side effects than a Moog Etherwave Standard or Plus Theremin.

I know a few people who found (sometimes with my help) working solutions :

a) Moog Etherwave Plus Theremin (modified for battery operation) + Roland Micro Bass RX Amplifier + a grounding wire/strap to link the player's ankle to the system.

b) Moog Etherwave Standard Theremin + Behringer KT-108 Amplifier + 12V->230V converter from the cigar lighter plug of a car, the latter slightly modified to use the whole car as virtual ground.

Thierry said: “A theremin has to be grounded in the same way as old long wave radio receivers had to. This ist nowadays normally done by connecting the theremin to an amp which is grounded through its 3-prong wall plug. The theremin's power supply itself provides no grounding to prevent other nasty effects like noise and hum induced by so-called ground loops which are created by multiple grounding of the same device chain.”

This is so right on, there use to be arguments around here on the importance of this subject. There is more involved than just a capacitive loop to the player. My solution if you Busk in the same place all the time is to be near a flower bed and pound in a 1 meter metal rod and leave it there until next time. On an EWS I would use a Y adapter at the audio output to have easy access to a point to connect to ground. Another method to razor blade off a piece of insulation on your ¼” cable to the battery powered amp to expose the outer shield or metal braid. Alligator clip from here to connect to the earth ground rod.

PS: If your theremin playing is mostly noise none of the above really matters.

Christopher

You can carry a short metal peg and water it with Coca Cola (contains orthophosphoric acid, a good conductor).

Regular water can also be used instead of Coca Colа.

(Hey Christopher!)

Hello ILYA,

For those that actually express themselves through the real Voice of the Theremin Phenomenon, I always thought there needs to be a gadget to measure the quality of the earth ground they are using.

Many places if wired correctly may no longer be properly connected to earth ground due to corrosion. The authentic theremin voice is shaped from Nature and is not a muffled flute/whistle buried in reverb. 

The Classic sound is sometimes human like. –

The end is near, a least for me! LOL

Christopher
 
I think digital better serves us in the control of information & knowledge (AI) not mimicking analog. I spent many years trying to figure out the Stock Market.

Success: If you look under the current date 11/17 between the two vertical black lines on the left side my computer places a box around stock symbols I might buy on Friday so I will profit this upcoming week. 

With digital some will succeed with Don's "Incredible Secret Money Machine"   (1940 to June 2023, age 83)  Obituary

https://www.oldtemecula.com/+TheGame.htm

"... I always thought there needs to be a gadget to measure the quality of the earth ground they are using."  - oldtemecula

This would be reactance, or AC impedance.  Drive a resistor to ground with a sine wave function generator set to the operating frequency of your Theremin, measure the voltage across it, and then calculate the ground resistance given the value of the resistor and the voltage ratios.  The question is what to connect the other side of the function generator to - one's hand?

dewster

Seems we are almost alone at TW anymore. I thought you had the concept until you mentioned the hand.

From the tank circuit out to the distance of the wavelength of the frequency being used, the ideal resistance should be zero. The higher the resistance, like above 10 ohms, distortion in the pure sine wave begins to appear . . . when monitored with a scope.

The RF wave shape transposes into the audio frequency wave shape. Distortion is wanted but should only be introduced by the control of the design. The EWS never took full advantage of timbre control, why it has a muffled sound without brightness.

Happy Holidays

oldtemecula

In the new Etherwave a power supply without a third wire to ground is used. The sound remains clean, even if a battery amplifier is used. For me a remarkable solution, for the moment I am wondering, how this was solved. Has someone an idea or know the Moog solution in detail? 

"In the new Etherwave a power supply without a third wire to ground is used."  - JPascal

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?