Bending radio: getting silent output safely

[jorgen]

Hello!

I've just gotten started with circuitbending and I'm having fun with some radios. I use a telephone mic on the speakers to record sound without fear of dying from electroshock.

However I'd like to route the sound through some software effects, without getting the pure sound from the radio itself (which is superloud, that's cool but a bit unpractical). On a workshop I was told I should never ever connect the output of the radio to a soundcard etc; no direct connections between my fingers on the circuitboard and something plugged in the wall..

Is there any way to do this?

[PHOBoS]

I think the best/safest way would be to use an audio transformer. They are available with a low input impedance of 8 ohms (primary) and high output
impedance >1K (secondary). So instead of the speaker you use the primary winding of the transformer and your secondary would be your line out.

[jorgen]

[PHOBoS]

the transformer would replace the speaker so if you have enough room for it then put it inside the radio. But it might be usefull to put it in a seperate box
so you could use it for other devices aswell. If you allready have a seperate audio output on the radio you could use that too, but you might need a
different transformer.

as for safety, I think the only way safer would be some sort of optical connection,. it's pretty safe. It's actually the same as what you do with a
pickup coil: the speaker coil is the primary winding, the pickup coil the secondary.

[jorgen]

[richardc64]

Wait a second! WHAT kind of radio? If it's tubes ("valves" to you UKers,) then yes, don't touch the innards while it's plugged in. If it's "Solid State" (transistors, ICs, etc.) it almost certainly has a power transformer to step-down the AC ("mains") voltage -- just like the power supplies we build. There's no electrical hazard.

FURTHERMORE, if the radio's output uses a transformer to power the speaker, you can connect directly to that transformer's secondary, perhaps through a switch that disconnects the speaker.

Really, one can't call oneself an electronic hobbyist until you've gotten zapped a few times.

Paging RF.

[jorgen]

[richardc64]