First Power Amplifier Build - Need some help


2016-01-26 10:52 pm
Hello All,

I'm in the process of building my very first power amplifier, and I've blown up my output stage twice already.

I was wondering if anyone could take a peak at the attached LTspice schematic and let me know which parameter of a TIP41/TIP42 that I'm exceeding?

I had both positive and negative rails fused with 1A fast blow fuses, so I'm thinking it's voltage related, not current but I could be wrong.

I also had a thermocouple clamped to the case of the output transistors and they are in the 42-46 degree celcius range when running a 5vpp sine wave into the input and getting 50vpp on the output into an 10 ohm test load (resistor).

Heatsinks are Aavid Thermalloy HS350-ND (3.7C/W) - Maybe too small?

I originally had 0.1 ohm resistors for R9 R10 R15 R16 but have changed them to 0.47 Ohm in hopes of spreading the load more equally.

Any help would be greatly appreciated!

Thank you

View attachment Power