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Old 19th August 2012, 04:44 PM   #31
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I have come across a few cheap mp3 players, that need a fairly low resistance load to function. They often use the headphone load as part of the filter circuit.
Maybe the player went into protection mode as the output caps charged up.
I always fit a bleeder resistor anyway at the input of any amp.

Are you using a SMPS to power the amp ? Often these outputs will float at about 1/2 mains voltage. then add in the -3000v of static from your hands and poof!
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Old 19th August 2012, 06:44 PM   #32
Mooly is offline Mooly  United Kingdom
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Good point whizgeek. I've never scoped the output of an MP3 player but what you say makes sense about the low impedance load being needed. There could be all sorts of HF hash there too.
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Old 20th August 2012, 05:35 PM   #33
vputz is offline vputz  United States
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Whizgeek: it's not an SMPS, it's a simple toroidal transformer with a diode bridge and caps (a bog-standard "gainclone power supply" as shows up in a number of places).

I'm still puzzled. The silly thing looks like it's operating fine now, but it was completely insensitive to the power switch for about 3-4 days.

Good point on the bleeder resistors too. I'll take a look and edit, although as mentioned it seems to be all happy again. Bizarre.
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Old 21st August 2012, 10:36 AM   #34
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You are mentioning an UPS in some post. I hope it is sinewave UPS.

Gajanan Phadte
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Old 8th October 2012, 09:42 PM   #35
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I had the same thing happen years ago with a portable CD player that I used for testing (specifically because it was battery powered,and isolated).
No idea what happened,I can only surmise that somehow DC came out of the amp's input,and cooked the CD players output stage.
Ever since then I've used input caps,purely for DC-blocking,and haven't had any similar issues.

One other good thought is HF crap coming out of the MP3 player. I know my iPod has some noise and crap on the output. Perhaps your amp didn't like being fed some random several-hundered-khz signal. I dunno.
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Old 10th October 2012, 04:54 PM   #36
AndrewT is offline AndrewT  Scotland
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DJ, if you read the thread you will find that the alleged action/question of
Quote:
My gainclone ate my mp3 player?
did not happen. He made a mistake and then discovered that the Power Amplifier did not damage his Source.
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