Making RCA Theremin play with modern amped speakers

Posted: 3/17/2007 9:23:48 PM

Joined: 3/20/2005

I am the proud owner of a fully restored Theremin (thank you Chuck!). I play it with an original 106 speaker and it sounds great. I'd like to patch it in to my regular audio system. I know I need a transformer, but I don't know the details about the 1929 Theremin's signal.

If anyone can ovver advice, I'd appreciate it.


Posted: 3/18/2007 12:16:43 AM

Joined: 10/8/2005

The high voltage (B+, a couple hundred volts) goes through the 106 speaker winding. You need to not only match somewhat the impedance of the theremin output to the amp input but also isolate the high voltage from the amp. As you suspected you need a matching transformer. I would try an impedance of about 1-2000 ohms on the Theremin side to whatever the input impedance of the amp input is or the modern speaker you are driving. You may have a lot of AC hum because the Audio amp on the Theremin doesn't have the gain or amplify the hum like a modern amp does. You can pick up the audio before the Theremin last audio stage off the grid through a capacitor and you will have a lot less hum. Your amp will more than make up for bypassing the last audio stage.
Posted: 3/18/2007 12:22:38 AM

Joined: 3/20/2005

Thanks for the reply.
I don't know about tapping the signal earlier than final output. I am not that expert on tube technology or even modern electronics. So I need a transformer that will go from 1-2k imped. to 8 - that's my speaker. I will give it a try!

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