LEDs interfere with radio

[spadefoot]

What I don't understand is, why doesn't the feedback loop continue until, in a very short space of time, the amp is driven into full-on hard clipping, closely followed by speakers or amp-chip burning out? Why is the feedback loop self-limiting, and why does it not exist when the aerial is working properly?

[Iain_S]

Radio receivers these days have an Automatic Gain Control, which attempts to keep the signal to the audio stage at a constant level. This would provide negative feedback, limiting the volume.

[spadefoot]

Ah, AGC. Yes I can get me head round that. As you've probably guessed, I know very little about radio (more of a guitar amp chap), was just trying to understand the logic of the problem.

[Top cat]

I've just remembered that back in the days we had a modified sine wave inverter every time the inveter was on you got a buzz from the rear speakers even when the radio was off. As for running the radio with the inverter on forget it. The mains wiring is in its own conduit well separated from the speaker wires.

Which just goes to show just how good those long rear speaker wires are as aerials.

 

Top Cat

[spadefoot]

I've just remembered that back in the days we had a modified sine wave inverter every time the inveter was on you got a buzz from the rear speakers even when the radio was off. As for running the radio with the inverter on forget it. The mains wiring is in its own conduit well separated from the speaker wires.

Which just goes to show just how good those long rear speaker wires are as aerials.

 

Top Cat

Which just goes to show what a dumb idea they are.

[Top cat]

Well when I fitted the rear speaker leads we were running halogen bulbs and didn't wish to listen to the radio with the inverter on. And we had no problems. The buzz was a useful reminder that the inverter was on, and since going full sine wave we have forgotten to turn the inverter off overnight a couple of times, so now we have a warning light.

It was only the combination of LED bulbs and a corroded aerial lead that caused the problem so no I don't think running speaker wires to the back was daft. Fixing the aerial has cured the problem.

The alternative was to buy a second radio with all the issues of installing it especially fitting a second aerial.

 

Top Cat

[spadefoot]

Portable radios?

I don't know your set-up, but if you have batteries at the back, a car radio somewhere near the front & speakers near the back, that could mean perhaps 50m of there & bask cabling from batteries to speakers. That's a lot of potential voltage drop. Maybe you have nice fat power feeds to your radio (6-10mm). If you're using car type speakers as well, the power losses are really quite big. Maybe you like listening to music quietly & the problem doesn't show up.

Your boat, your set-up, if it works for you that's all that matters.

I use portables, (dab radio & boombox) flexible & power thrifty, important for me as a live-aboard.