Master Thread: Are Measurements Everything or Nothing?

[RDoc]

SINAD isn’t a perceptual model, and it doesn’t need to be.

Once all distortion components are below audibility, changing the weighting doesn’t make them audible again.

As to higher order Class D distortion: where?

If you agree SINAD isn't a perceptual model then why is it the metric used to rank electronics? It seems to me that the point to these rankings isn't how technically perfect the devices are, but rather what they do to the perceived sound. If that's the goal, ranking by technical measure then I'd think it would also be useful to reprocess the FFT numbers to give a perceptual score which is what most people are interested in.

I totally agree in modern amplifiers high harmonics are mostly a very low levels, but if we're discounting harmonics below some level, say 100 DB, why even include them in the calculation? Noise is different since it is generally less sensitive to volume level. Other systems like GedLee do take that into account by the way their weighting works.

Higher order harmonics are in the example you show for the Topping.

 

[RDoc]

There's no distinction in the SINAD number between noise and distortion. I'm guessing that the 115 dB threshold is for the worst case scenario, where it is the noise that dominates. And you have a quiet room and your volume is set to listen highly dynamic material very loud, in which case you could maybe hear the noise when nothing plays if the SINAD was lower than 115.

Low volume would be more of an issue I'd think since the noise floor is not very dependent on volume.

 

[voodooless]

If you agree SINAD isn't a perceptual model then why is it the metric used to rank electronics? It seems to me that the point to these rankings isn't how technically perfect the devices are,

It is exactly that. Nothing more, nothing less. And then even in this singular metic, so most certainly not all-encompassing. But as a general guide for engineering excellence it works pretty well.

but rather what they do to the perceived sound. If that's the goal, ranking by technical measure then I'd think it would also be useful to reprocess the FFT numbers to give a perceptual score which is what most people are interested in.

What for? The vast majority of these products are audibly transparent.

I totally agree in modern amplifiers high harmonics are mostly a very low levels, but if we're discounting harmonics below some level, say 100 DB, why even include them in the calculation?

Because that is how THD+N is done..

Higher order harmonics are in the example you show for the Topping.

Sure, but way below audible levels. Most non Class D amps will not do much better, contrary to what you want us to believe.

 

[antcollinet]

If you agree SINAD isn't a perceptual model then why is it the metric used to rank electronics?

Becuase it tells us how good the device is at being a "straight wire with gain" In most cases it also tells us that the noise/distortion is going to be inaudble - so a perceptual ranking is unnecessary. If it doesn't, then we can look at the other measures - which show a more detailed breakdown of distortion so we can decide (if we are even prepared to consider an audibly distorting device) what that looks like.

 

[Sal1950]

My Adcoms were great, and at the time, the 5802 was a great watts/$ solution for my brutal Thiel cs3.6 speakers. But holy crap was it hot, and had to be recapped a couple of times.

Ouch, I've had no experience with that amp but a quick gaagle brought me to Hoppe's Brain, a highly respected restorer of Adcoms and he fully agrees with you on this monster. Just looking at the board layout scares the hell out of me. A Bad Guy, I'd advise avoiding this one at all costs.

"UPDATE: 2021.04.26:
I get a lot of emails about the GFA-5802, from people looking to repair one that has cooked itself to death. I have no parts for this model, and generally speaking, I don’t sell parts, except for those that come with my PCB kits.
I stopped working on this model a long time ago; it’s just too problematic. The GFA-5802 is essentially a budget version of a Nelson Pass-esque amplifier—though he did not design it—and IMO, too many corners were cut to meet a price point. For one thing, there is not nearly enough heat-sink for an amp with this much idle current consumption.
My issues with this amp are outlined here in this thread on DIYAUDIO.COM. I am forum user “Phloodpants”.

 

[Mnyb]

Distortion above 10kHz is also less off a concern as second harmonica is 20KHz and the rest is at even higher frequencies the mechanism behind these could possibly cause imd , but these are tested in the 2 tone test where the latest class D do really well .

Perceptual ranking migth be needed for ”bad” amps tubes etc where we have 1960’s levels of distortion ?

 

[Mnyb]

Distortion above 10kHz is also less off a concern as second harmonica is 20KHz and the rest is at even higher frequencies the mechanism behind these could possibly cause imd , but these are tested in the 2 tone test where the latest class D do really well .

Perceptual ranking migth be needed for ”bad” amps tubes etc where we have 1960’s levels of distortion ?

Forgot the obvius !

For speakers this migth not be such a bad idea , they will not have inaudible distorsion any time soon

 

[ahofer]

Ouch, I've had no experience with that amp but a quick gaagle brought me to Hoppe's Brain, a highly respected restorer of Adcoms and he fully agrees with you on this monster. Just looking at the board layout scares the hell out of me. A Bad Guy, I'd advise avoiding this one at all costs.

"UPDATE: 2021.04.26:
I get a lot of emails about the GFA-5802, from people looking to repair one that has cooked itself to death. I have no parts for this model, and generally speaking, I don’t sell parts, except for those that come with my PCB kits.
I stopped working on this model a long time ago; it’s just too problematic. The GFA-5802 is essentially a budget version of a Nelson Pass-esque amplifier—though he did not design it—and IMO, too many corners were cut to meet a price point. For one thing, there is not nearly enough heat-sink for an amp with this much idle current consumption.
My issues with this amp are outlined here in this thread on DIYAUDIO.COM. I am forum user “Phloodpants”.

LOL, I spoke to that guy when I sold all my old equipment and got the run-down. Live and learn.

 

[Sal1950]

LOL, I spoke to that guy when I sold all my old equipment and got the run-down. Live and learn.

Yes he's one of the good guys, mostly honest and straight forward.
It's difficult to justify putting any real money in these ole amps but thats just my opinion.

 

[EJ3]

most audiophiles say that it sounds awesome

Which definition of audiophile might that be?
I could be defined as one, most of my gear measures around 90-95 SINAD (with the exception of my phono and tape (cassette & Reel to Reel) stages, which measure between 70 & 79 SINAD (depending on which one I am using [not the tape decks themselves]).
I find that (in my home, with it's inherent noise floor): it's all just fine.
(on my TT: the needle drop is silent, as the cartridge circuit does not engage until the needle has touched the records surface, so no needle drop noise).
Which also translates to my tapes made by me.

 

[ahofer]

This is worse looking into...

I think I agree with that.

However, there is quite a lot of discussion of harmonic (or other) distortion and its potentially enhancing audio effects. @pkane even has a product that simulates it.

What I don’t understand is why you would want a really expensive piece of jewelry that fixes your distortions in one particular way regardless of the characteristics of the signals you are feeding it.