buffers overheating in pimeta
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americandreaming

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just finished my first pimeta a few nights ago, ran a few tests, and then listened with cheap phones for a while. it sounded good but when i played it again last night it sounded terrible with distortion that sounded like it would rip the inside of the headphones to shreds. you could hear it slightly at low levels and it was really bad at moderate levels.

i noticed the buffers on the left and right channels were very hot. i plugged it in again today for some more tests and got the same results. through my cheap headphones it doesn't sound that bad today but still very hot.

i read tangent's guide to troubleshooting but i'm still a bit lost. do both buffers need replacing? what voltage should i be getting at them?
 
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mono

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Does the amp seem to be working ok if/when powered on initially after cooling down? IE- still working OK as you first reported and up until the buffers heat up?

Are they socketed such that you may remove them and take voltage readings at the power pins (see TI's PDF spec sheet if pinout needs referenced) ?

Is your source DC coupled or do you have the Pimeta coupling caps installed AND the trace under the cap manually cut? Point being, might there be a lot of DC offset? Measure DC offset between L & Gnd, then R & Gnd outputs.

What is the current draw of the entire amp from the power source and how is it configured (class A bias, opamp(s), # stacked L & R buffers, etc) ?
 
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