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Old 18th December 2003, 01:30 AM   #1
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Default Revised quasi pnp output amp

I originally posted this schem to see if someone else could figure out my issue with the vbe multiplier bypass capacitor making the circuit unstable and with help from EVA (thanks) I was able to redesign the amp into what it is know.

I feel pretty good about it but would like to see what others think about this amp.

It's fairly cheap for the quality and power but the fact that I use PnP outs instead NPN kinda makes it seem foolish, it's just what I had or could easily get.

Here is the original

And the new one

There are a few things missing from shem 2, I added 2 pot's one at r5 and one at r9, r10 to help with bias and offset sweet spot.

A big problem I had with the first one is if I ran it full volume from anything more then 25v +/- it would fail into full rail current going through one of the output transistors to the load??

I haven't used anything-higher then 40v +/- yet on the current design but it works and sounds good. I haven't done any distortion analysis other than my ears that of course are biased but I get 31v RMS into 4-ohm @ 60Hz load before audible distortion is heard.

My practical knowledge of electronics is way above my theoretical knowledge as I'm sure the pro's can tell, but any suggestion to improve this amp would appreciate.

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