Topping D90 vs Sony TV Audio out to Hypex 1200 Mono Amp

[alexis]

Hi, this is a DAC / Mono Amp combination question. I have a D90 connected using Balanced out to Hypex Mono NC500 and NC1200. The NC1200 is much hotter than the NC500. When I put the NC1200 with Sony OLED TV using audio out to balanced cable, the temperature is cool when using the same speaker (4 ohm load). I noticed the D90 has an output impedance of 200 ohm (Sounds like normal DAC has this) and I don't know what's the output impedance from the Sony TV. Both NC500 and NC1200 has SPMS 1200 as the power source in the Mono construction. I can accept the NC500 heat but NC1200 is too hot in my view. Does this have something to do if I pick a DAC that has different output impedance?

They all sound fantastic.

 

[DVDdoug]

I don't have an explanation but impedance between the line-level source and the line-level input shouldn't make any difference.

A lower impedance load does "draw' more current. (Resistance or impedance is "the resistance to current flow".) The input of the power amp is the load on the preamp or DAC so a low input impedance on the power-amp would tend to heat-up the preamp/DAC (not the power amp), but with a typical input impedance of 10K - 100K you're talking about insignificant milliwatts or microwatts. I wouldn't expect the temperature difference to be measurable.

Of course the load on the power amp is the speakers and that can make a difference.

One thing that can cause "unexplained heating" is ultrasonic nose, but I'd be shocked if the D90 is putting-out ultrasonic noise. I fried a power amp many years ago when I was trying to build a preamp and it turned-out to be an RF oscillator... I was impressed how with how quiet it was and I hadn't even put a signal through it yet when I heard a little "pop" from the speaker. I didn't actually notice the amp was overheating, it just died.

 

[alexis]

How do I verify this? So far I can only compare with TV output. The heat could be "normal" based on the high power of 1200. What puzzles me is why TV doesn't give so much heat with the same speaker on similar or larger volume. If there are similar dac that can "lead" to less heat, I'd like to give it a try.