I've got a 4 channel LM3875 (preferred it over the LM3886) amp, and while I only connected two channels so far, I noticed this on both of them, when I'm playing into a speaker there is the normal 50mV of offset, but as soon as I switch it off I get around -5V DC on the output, and it slowly declines. I don't know why this is so, it's like the ground is live, with 5V or so, could this be because I've not connected the ground to the wall ground? Or maybe it is because my test speaker has a high-pass filter (just a single capacitor) at a relatively high frequency (in the mid-band, so DC doesn't kill it while I do tests such as this one...)?
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