Need Help! My Class A Amp Is Running Very Hot

Imhififan makes a good point about the possibility that the amp is a 100 volt model being operated with 120 volts. The voltage the amp is designed to operate with should be indicated on the rear panel.

Regarding the Kill-A-Watt meter, I have no experience with and no particular knowledge of such devices, but I wonder about what kind of accuracy it would provide when used to measure the power consumption of a power amp or integrated amp. I assume that what it does is to multiply together a measurement of voltage and a measurement of current. But are those measurements "true rms," or something else?

And if they are not true rms, given that an amp draws current mainly during a small fraction of each 60 Hz period, when the instantaneous voltage of the AC at the output of the power transformer approaches positive and negative peaks and exceeds the voltage stored on the filter capacitors by enough to cause the rectifier diodes to conduct, that would seem to raise questions about how meaningful the measurement is.

Also, given the inductive nature of the power transformer and the capacitive nature of the filter capacitors, perhaps voltage and current aren’t quite in phase with each other, which would also result in some inaccuracy if the device calculates power consumption by simply multiplying the two numbers together. With the inaccuracy being in the direction of overestimating the number of watts.

Perhaps one of those having experience with these kinds of devices can comment on these questions.

Regards,
-- Al

the cabinet on the top temperature is 28C which I think is just a little warm but acceptable but when I put my hand on top of the plastic vents (over the heat shrinks) it is extremely hot, way over my thermometer maximum temperature of 50C

To add perspective, my Pass XA25 amp operates in class A and consumes an amount of power (240 watts at idle) that is very similar to yours. The XA25 is stated to be designed such that after it warms up to a stable temperature its heatsinks will be about 25 degrees C higher than the temperature of the room. (Elizabeth makes a good point about the significance of room temperature, btw. Each degree of difference in room temperature will make the same difference in the temperature the amp stabilizes at, following warmup).

So under typical room temperature conditions the heatsinks on my amp will approach 50 degrees C. Very significantly, however, in contrast to yours the heatsinks on my amp are on the outside of its cabinet:

https://www.passlabs.com/amplifier/xa25#lg=1&slide=8

The heatsinks on my amp also appear to have much greater total surface area from which to radiate the heat than the heatsinks that are inside of your amp.

So, again, it seems to me to be very possible that what you have described is normal, although I am not in a position to be certain about that.

Regards,
-- Al

The L-590AX is spec’d as consuming 220 watts at idle (310 watts max). The L-590AXII is spec’d as consuming 260 watts at idle (330 watts max). Both models weigh about 63 pounds. The amp’s heatsinks are entirely enclosed within its metal cabinet, and are immediately adjacent to the side-panels, as can be seen here:

http://www.luxman.com/asset/product/L-590AXII/gb4.jpg

So the escape route for the heat corresponding to those power consumption numbers is almost entirely via the vents on the top, supplemented to a small extent by radiation through the side panels.

Given all of that it seems to me to be very possible that what you have described is normal, but it’s hard to say for sure. Perhaps another owner of one of these models will chime in.

@three_easy_payments, I believe the OP’s reference to "cabinet" pertained to the metal enclosure of the amp itself.

Regards,
-- Al