Small switching amplifier up in smoke. Twice.

[Al3579]

I’m not sure this is relevant, but the bookshelf speaker that I’m using has an auto-shutoff to protect it from being over-driven. Although the volume wasn’t particularly loud, I’ve seen it shut off in the past from a quiet volume because it didn’t like the home-brewed signal I was sending it. Keeping in mind that I don’t know what I’m talking about, I was thinking that maybe the speaker shutting off caused some kind of inductive spike that overloaded the amp?

Here’s a link to the amp’s data sheet:    https://www.ti.com/lit/ds/symlink/lm4667.pdf

Thanks so much for any help you can provide.

-John Adler

I think its relevant, most bookshelf speakers with an auto off feature have a built in amplifier for the speaker. I have never seen a passive speaker with an auto off feature but I can be wrong.

[Al3579]

On second thought I have seen 2 wire subwoofers for home entertainment with auto off. Dc current goes through the wire to switch on and off a relay to switch the power amp on and off. Dc current plus modulated ac. You would think volume and bass controls were enough. They probably use it for dramatic effect to sell really junk systems. The up point is you can use that dc power to heat up the speaker to drops it sensitivity and have lots of power compression. Call it BoZe while your at it.