ATI AT522NC Stereo Amplifier Review

[RichB]

For the AT4000/6000 Is there something where shielding could be applied to the PSU to stop the noise, or is it the PSU itself?

I’ve wondered if 3D printing a case for the 1ET400A in ESD filament would net any positive results.

Shielding can help with noise on the outputs, though these amps are good in that regard.
Transformer hum, is more difficult because it is environmental. I had intermittent hum, though I had 3 dedicated 20 amp circuits.

- Rich

 

[MaxBuck]

I am of the opinion that the driving real loads, some amps may incur more distortion and linearity issues not readily found in reactive load, single tone testing.

- Rich

I was under the understanding that testing is typically done using resistive, rather than reactive, loads. Is that not correct?

When I think about amplifiers "sounding different," I think about the influence of complex reactive loads, which loudspeakers clearly are. Amplifiers with less robust design could, in my fevered and ignorant mind, feasibly strain to achieve the low distortion they exhibit with simple resistance. Am I completely wrong? (Don't think you need to spare my feelings here; I am aware I'm spitballing based on a primitive level of understanding.)

 

[peng]

I was under the understanding that testing is typically done using resistive, rather than reactive, loads. Is that not correct?

When I think about amplifiers "sounding different," I think about the influence of complex reactive loads, which loudspeakers clearly are. Amplifiers with less robust design could, in my fevered and ignorant mind, feasibly strain to achieve the low distortion they exhibit with simple resistance. Am I completely wrong? (Don't think you need to spare my feelings here; I am aware I'm spitballing based on a primitive level of understanding.)

In most reviews yes, but while Stereophile uses both resistor load and simulated speaker load that is reactive. I do not believe reactive load is a problem other than may be slightly higher (but still not that audible) distortions may result. It could be a problem in some cases if the load is highly reactive such as >45 degrees lagging or leading and leading may increase the chance of developing stability issues on lesser amps. That gets worse if the large angles coincide with impedance dips.

 

[RichB]

In most reviews yes, but while Stereophile uses both resistor load and simulated speaker load that is reactive. I do not believe reactive load is a problem other than may be slightly higher (but still not that audible) distortions may result. It could be a problem in some cases if the load is highly reactive such as >45 degrees lagging or leading and leading may increase the chance of developing stability issues on lesser amps. That gets worse if the large angles coincide with impedance dips.

The Stereophile measurements into a reactive load shows linearity issues that differ from amp to amp.
I have not seen simultaneous measurements showing distortion level and distortion frequency that would contribute to audibility.

An amplifier with a regulated power supply may perform better where the incoming AC fluctuates, say when the wind is not blowing.

- Rich

 

[peng]

The Stereophile measurements into a reactive load shows linearity issues that differ from amp to amp.
I have not seen simultaneous measurements showing distortion level and distortion frequency that would contribute to audibility.

An amplifier with a regulated power supply may perform better where the incoming AC fluctuates, say when the wind is not blowing.

- Rich

I agreed with such differences (e.g. linearity) that could be shown on paper but I have not seen evidence of those differences significant enough to contribute to audibility in general. I would like to see specific blind test results for real apples to apples comparisons conducted by relatively neutral and trustworthy such as scientific researchers. I don't think that will happen any time soon because academics/scientists have more important things to do (such as saving lives, curing cancer, improving the economy etc.).

 

[Head_Unit]

I am of the opinion that the driving real loads, some amps may incur more distortion and linearity issues not readily found in reactive load, single tone testing.

I am of the opinion you are very likely correct. Especially as passive reactive loads won't have any power level/motion related instantaneous variations in impedance (and maybe back EMF...well I guess that is motion related also). However I am also agreeing with @peng that we probably won't see this in our lifetime...

 

[FRL]

I've have the 3-channel version of this ATI amp - 523nc driving a mixed AV 3.1 system for the past 3+ years. Did some critical listening this weekend because I had the upgrade itch, and I came to the conclusion this amp is pretty awesome and it'd be foolish to try to upgrade that component of the system.

This amp has been rock solid reliable and revealing of the changes I've made upstream in this system - DAC, Pre, CDP. I know a lot of people crap on Class D as cold/dull, but this ATI hypex line is worth a look if you value neutrality, compact size, low heat, affordability, and plenty of power for most applications. Speakers are KEF R Series.