ILoveHiFi wrote:
2.5A results in about 58-60C in a 20C ambient
The SMPS is hot and the transistors are near thermal limit if you take into account of heat trasnfser limits
The amp swings +-2v to rails
Thermal management is a big issue for power amp. You don't have enough power of the SMPS. You peak current for each channel is 22V/8=2.75A. For stereo you can have the same signal on both channel at the same time, you peak current is 2 X 2.75 = 5.5A. Your SMPS might shutdown. That's the reason I started out with 10A supply. Then I still have a lot of cap as reservoir. That's why it turned out it's cheaper to use torroidal power transformer and do it the conventional way.
Particularly I am doing dual monoblock, that is each side of the amp is independent to the other side, Each channel has it's own transformer, it's own filter caps, totally separated from each other.
For class A swing to 22Vpeak, for 8ohm load, you need bias current of 1.375A minimum. for +/-24V, the dissipation is 48 X 1.375 = 66W/ch. Your chassis barely big enough. It will get very hot already. Your chassis is about the same size as my small one, I run about 60W heat, it's hot.
For +/-24V, you get 30W of class A power output into 8 ohm. That's the reason I do high bias class AB instead. I run 1A bias, that gives me 16W of class A power, and 58W of total power. My amp is low power for 8ohm, but I design the amps to be able to drive low impedance easily to 2ohm or lower. My speaker is 4ohm, so it is a 116W amp.
My big chassis is a 50W class A chassis, I can get 100W into 8 ohm or 200W into 4ohm.