Recently i made a gainclone based amplifier & faced a weird phenomena. For test purpose i was using a simple opamp gain stage(6dB) to boost the output signal of a Bluetooth mp3 player. For preamp & mp3 player i used 7xxx based regulated power supply. Anyway when i was turning off the whole thing there was a terrible loud thump /squealing after 1-2 second. I tried different opamps (5532/072/353) but result was the same. I checked almost everything but i failed to get any clue. The mp3 player was connected to the positive rail of the preamp, to find the problem when i disconnect its supply(5v) everything becomes normal, no turn off squealing. Then i realised it was happening because positive rail collapsing faster then the negative rail & it turned out to be true! I added a LED load to the negative supply rail & voila! No turn off squealing now 🙂
I thought i should share this with everyone. Anyway have a nice day folks!
I thought i should share this with everyone. Anyway have a nice day folks!
why would i need muting circuit? lm3886 doesn't have any thumps when switching the power on or off, dead silent i mean 😎
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Has its own protection or muting circuits..
Muting circuits mute on power On / Off until Voltages are stabilized.
Digital stuff like CD, BT or mp3 players usually have muting transistors in the outputs, or You would hear digital noise when idle / track skipping.
On the cheap ones You hear a "plip" or "plop" when skipping tracks or between play stop.
