Turn on pre driver stage first or output stage first?? - diyAudio
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Old 6th December 2011, 08:29 AM   #1
Leolabs is offline Leolabs  Malaysia
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Question Turn on pre driver stage first or output stage first??

For a power amp with separate pre driver stage & output stage power supplies,to reduce turn-on thump(WITHOUT using relay for the speaker path)
should turn on pre driver stage first or output stage???
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Old 6th December 2011, 11:28 AM   #2
AndrewT is offline AndrewT  Scotland
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Good question.

I would like to see a design paper on how to achieve quiet power up and quiet power down.

I will start by suggesting that the output pair will have output offset if they are not matched for Vbe/Vgs for all the currents from zero at start up to full bias current.
This seems an impossible constraint on device selection, so there must be a way of suppressing the output offset changes as the output pair start up.
What operational conditions do we need at the input PINs to the output devices to ensure no changing output offset?
eg. shorted input PINs to Audio Ground?
input PINs shorted together?
or ??
regards Andrew T.
Sent from my desktop computer using a keyboard

Last edited by AndrewT; 6th December 2011 at 11:30 AM.
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