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Old 7th May 2005, 09:28 PM   #1
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Default reducing dc offset on sub plate amp?

hi there, i'm looking for any advice on reducing the dc offset at output wires on my PE 240 watt sub plate amp. just maybe, some types of approach which apply to most amps in general that i could try. i have no turn on thumps, or other problems such as heat and have between 70 and 80 mv right now after, upgrade from original output transistors. 2sd1047/2sb817 changed to mjw3281/mjw1302. the performance is so much better now that i don't want to swap back but, would like to reduce the offset level some if possible. thanks for any advice, crippledchicken
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Old 8th May 2005, 10:54 PM   #2
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Did you look at the offset before you changed transistors? I'd bet it was about the same.

The offset in most plate amps I've seen is not adjustable, which means examining how the amp works and determining what measures it uses to deal with nulling offset. Most home amps rely on feedback to differential pair transistors to compensate and null the offset. In these cases the only method is to replace the differential pair transistors with a closely matched pair.
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Old 9th May 2005, 01:51 PM   #3
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Quote:
Originally posted by EchoWars
Did you look at the offset before you changed transistors? I'd bet it was about the same.

The offset in most plate amps I've seen is not adjustable, which means examining how the amp works and determining what measures it uses to deal with nulling offset. Most home amps rely on feedback to differential pair transistors to compensate and null the offset. In these cases the only method is to replace the differential pair transistors with a closely matched pair.
hi EchoWars, you are verry correct! good call thanks. i put the originals back in which don't sound as good and darn it, the offset was even a little higher he he. so, i guess you know what i did next. i'll make sure to aLWAYS, measure offset before removing original outputs on anythig else. and save myself alot of foolish trouble maybe. thanks for your verry educated reply! crippledchicken


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Old 6th October 2007, 06:06 AM   #4
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Hi there, was the 2sd1047/2sb817 original Sanyos or cheeper clone devices?
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