Amplifier died after working for a while!!!!

I would start by measuring the quiescent current in the output and driver transistors. Also, see if there is any DC current flowing to the speaker.

Tam

Sounds like thermal runaway. Did you thermally couple Q9 to Q5 and Q6?

Q9 is supposed to do thermal compensation of the output quiescent current.

for one thing, the VR1 is there to reduce the current to it's minimum and most likely used to balance the output to 0 volts with no signal on the input while making adjustments.

You don't show how you have mounted your power transistors?, I do hope you are using heatsinks? And I hope you are monitoring the heat level ..

It most likely burned up with excessive bias through the output transistors... This is not a good design, there is no necessity for bootstrapping the output stage in a modern circuit...

"Fred Bloggs

Slaves to audiophool, voodoo inspired fashion are asinine f*****ts indeed !!!!!!!!!!!!!!!!!!!!!!!!!!!

The Bloggs congenital, autistic, MORON regularly obliges, on cue - as usual .......

Bowel cancer is too good.

...... Phil

Perhaps you would have been better to have built and tested the design as given before trying to improve it with your own modifications. . . .

when i did not connect a speaker, i can not measure the voltage drop across power resistor.

Yes I have one, but I think the problem may be there. When the heat increases more and more then the amp die. Today i will make the board with the enough big.