Hey guys,
I want to build a tiny guitar amplifier and my drawer full of LM386's isn't cutting it. Are there any IC's that are currently manufactured that do at least 3W and are similarly as easy as the LM386 and ideally include some protection for overheating, etc? 

If not, maybe my best bet is to add a push-pull transistor output at the end of an opamp stage (like in the attachment) - but I don't know how I'd chose the resistor values or the transistors to get 3W safely.

Hey everyone,
I've been given a Peavey LTD 400 that isn't working, it has 40VDC on the output. I've taken every power transistor out and tested them (diode setting on multimeter) and they all test fine.

Attached is the schematic with all of the DC measurements I've taken around all of the other transistors. Since I don't know what the voltages should be, I'm hoping someone can help me narrow down where the problem might be.

It seems as though this is a "Transistor Darlington NPN 150V 16A 200W" according to google.
I'm looking for a replacement (reassigning the pin-out isn't a problem) if anyone knows one?

This is for a Yorkville 150B whose speaker cord shorted out while playing.

Thanks guys!

Hey guys,
I recently inherited a Legend A30 with some problems in the output section. It looks like repairs were attempted, some capacitors replaced etc. I've tried my best to troubleshoot the output section, but to no success since the whole situation is complicated because of the previous attempted repairs.

The output looks correct on the scope when there is no speaker load attached. As soon as a load is attached (speaker or dummy), the output quickly drops to be nearly silent. The only thing that comes out of the amplifier is highly gated sounding, and on the scope appears to be just the very tops of the positive peaks (but inverted) of the signal going into the power section.

Attached is the relevant part of the schematic (full schematic here: http://music-electronics-forum.com/attachments/24638d1376247077-30watt1_1.jpg ) and I've also shown a bunch of test points and the results of the scope measurements I made at each of those test points, both with the load attached and with the load disconnected. I also wrote up all of the transistors in this section and what they've been replaced by. The schematic is hard to read, so there's a question-mark next to a few. Also note that Q12 (D41ES ?) was replaced with an A706 and the pin different pinout looks to be correctly compensated for.

I hope the diagram helps, let me know if there's anything you'd like me to test.

Thanks again,