Enough noise reduction?

We get the S/N+THD specs, and these assume ideal AC power.

I highly doubt that Stereophile and ASR are using lab power supplies for their measurements.

ASR’s SNR measurement of the Ares II puts it at 120 dB using the balanced out, so excellent performance without aftermarket power cords.

You will most likely never hear any sound at -120 dBFS unless you’re in an anechoic chamber and even then the noise that your own body generates will probably dominate your auditory sense.

To give you a more practical demonstration, try this sound test at Audiocheck.net. It plays a voice decreasing at 6 dB intervals starting at full scale level. Adjust your volume control so the first voiceover is at the usual loudness you listen to. Once you can barely hear the voice, you’ve found the lowest threshold of noise you can detect.

@holmz 

I'm still doubtful a lab power supply is used. It just doesn't make any sense. A lab 'bench' power supply provides DC, not AC. Also, these components are consumer products meant to operate off of standard household power. If you want to measure and test them, wouldn't you want to know the performance given wall power?

Anyway, I've done an online search which didn't uncover anything definitive. I sent an email off to Stereophile. I'll post an update if I get a response.

@holmz @erik_squires 

I just received a reply from Diego Estan who was recently hired to measure the equipment under review for the SoundStage Network of web sites. I asked whether or not he used special power supplies for the equipment under test. Here is his reply (edited for typos):

To answer your question, absolutely not. All devices under test, [other] than amplifiers and integrated amplifiers, are directly plugged into the same, standard 120V/15A circuit, as the Audio Precision analyzer. This is a typical circuit in a spare bedroom of my home and is shared with lighting, my home PC, etc. 

 

For amplifiers and integrated amplifiers, these are plugged into a dedicated 120V/20A circuit, and the minimum observed AC line voltages are provided in the report. Nothing else is plugged into this circuit other than the amplifier. There's only one 20A electrical outlet on this circuit, and it's a relatively short run to the electrical panel.  

 

I live in Canada, and electrical code dictates 14ga solid copper for 15A circuits, and 12ga solid copper for 20A circuits. 

 

I will also say that my home is relatively new (2012), and I have pretty stable power.