battery powered amp/speaker for busking

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.

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.

Sorry I don't have any suggestions at this time, Zigg.

I see there have been no responses here.

Where are you with your project now?

Zigg,

I just found this manufacturer's description:

Compact, lightweight at just 2 pounds, and completely portable, the 302 sets up in minutes, with battery operation eliminating the need for an external power source. Its high-impact-resistant ABS plastic case ensures durability and reliability. When used with a mic stand and a battery-portable amplifier such as the Roland® CUBE Street, the 302 permits a theremin performance virtually anywhere. Equally suited for the studio, the 302 also provides unexcelled results for use in recordings and soundtracks. Thoroughly evaluated in the rigors of harsh travel environments, the 302 has been perfected and tested by thereminist Arthur Harrison in every-day, practical use, in both indoor and outdoor venues.

http://harrisoninstruments.com/302/302_description.html

The theremin does work with the roland cube amp.

Maybe your cable wasn't long enough and on the ground to give you good GROUND.

The theremin does work with the roland cube amp.Maybe your cable wasn't long enough and on the ground to give you good GROUND.