Remarkable article about amp distortion

[SpursGator]

This is my first post in years - I'm back just to share this.

I bought a Benchmark DAC1 the year it was released, long before Benchmark knew they were an audiophile company (Dec. 2002). I've been on their mailing list ever since and I never paid much attention. Today they sent me this. It obviously favours their amp, but this article is a remarkable read for any audiophile:

How Loud is the Distortion from Your Power Amplifier?

We took Stereophile's THD+N plots for 7 top-rated amplifiers and replotted the data to show the loudness of the distortion and noise at the listening position.

benchmarkmedia.com

 

[RJW232]

I haven't read the article in detail, but if my interpretation of the graphs is correct, distortion will be at washing machine level if the sound pressure is >115dB. Even rock concerts are limited to 103 dB SPL. At living room SPL's (80...90 dB), the noise+distortion is ~20 dB, probably lower than ambient noise in the average room.

 

[Jasonovich]

This is my first post in years - I'm back just to share this.

I bought a Benchmark DAC1 the year it was released, long before Benchmark knew they were an audio company (Dec. 2002). I've been on their mailing list ever since and I never paid much attention. Today they sent me this. It obviously favours their amp, but this article is a remarkable read for any audiophile:

How Loud is the Distortion from Your Power Amplifier?

We took Stereophile's THD+N plots for 7 top-rated amplifiers and replotted the data to show the loudness of the distortion and noise at the listening position.

benchmarkmedia.com

It's a great read, unfortunately my brain started to vegetate halfway through, you can call it grey cells distortion.
Distortion is all around, when you put your needle on the record, when you listen to your tube amp but not all of it is welcoming.

 

[SpursGator]

I haven't read the article in detail, but if my interpretation of the graphs is correct, distortion will be at washing machine level if the sound pressure is >115dB. Even rock concerts are limited to 103 dB SPL. At living room SPL's (80...90 dB), the noise+distortion is ~20 dB, probably lower than ambient noise in the average room.

What I thought was so interesting was how much more useful these graph plots were - especially looking at the different profiles of how Class D and AB amps deal with 4 ohms vs. 8 ohms. It would be so helpful to see plots of this nature for every amp. It answers so many more questions about how the amp performs than the data we are given as consumers - even though it's the same data! Just replotted.

The fact that Benchmark's own amp performs so well is practically a footnote. The AHB2 is already widely regarded as one of the quietest amps around.

RJW, you should look again more closely! 105 dB is a typical volume for movies, for which an awful lot of people use their amps. At that volume, distortion will clearly be audible from 99% of the amps on the market, especially in certain amp/speaker combos that happen to be very common (e.g., a class D 7-channel home theatre amp driving inefficient small speakers).

On the one hand, this shows how misleading the "0.00x% THD" stat is. On the other hand, it goes a long way towards explaining why different amps sound so different from each other despite appearing to have similarly microscopic levels of distortion on paper. Which I found quite enlightening.