NOS DAC - Marketing BS? - Page 19

The thing is fatiguing highs are in the audible range. So what you're hearing has less to do with NOS or OS and more to do with the quality of the DAC chip and its implementation.

You may be familiar with the sound of sloppy bass. It sounds louder, fuller, but it's also boomy and if you listen to that for a while your ears will start to hurt (especially if corner-loaded). It's the same idea with treble. Sloppy (i.e. distorted) treble will hurt your ears, especially when you turn up the volume. It's worse in reflective rooms.

So one way to avoid this problem is to roll off the highs. Tubes are often used to accomplish this. But what if you got a DAC that didn't have that problem in the first place?

The standard set of published measurements doesn't reveal this problem. Multitone THD+N measurements are helpful here.

Linear pretty much means what you expect from math class. You always want the output to match your input. If at certain values that no longer holds true, then your function/device becomes non-linear at those values. It is rare, but sometimes you'll find linearity measurements for DACs. I have one posted on my site.

With an amp, a simple example is when you ask it to do too much. It will start introducing distortion and fail to provide the power you are asking. The sound will break down.

You're correct. If you just have a number, like 1% distortion, that may mean a huge 2nd harmonic, or a whole lot of somewhat smaller harmonics. So a 1kHz FFT graph can be a lot more informative than just the number. But that's only at 1kHz. I don't think you'd enjoy looking through 20,000 FFT graphs.

Would you guys care to comment on these links from 00940?

(LP listeners are gonna love this)

The gist is that the band limiting filters used to reduce a recording to redbook spec produce pre ringing on a recorded square wave. It's a normal consequence of limiting the bandwidth.

Does this mean that all cds, and all 44.1/16 files, have pre ringing as a result of being formatted to redbook if there are sufficient transients in the music?


Here is a quote from the first link, page 2 -

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"Guido and dddac,
You had best listen to Werner - he really knows this stuff.

Werner accurately explained why the first waveform has "ringing". It is because a true square wave has frequency components up to infinity. When you limit the bandwidth of the sqaure wave, you will get exactly what is seen in the first picture. The "square" wave is now approximated by only the first few harmonics... 1 kHz, 3 kHz, 5, 7, 9, 11, 13, 15, 17, and 19. The result will not, and must not look like a square wave any longer, because it is not, by the fact that the higher frequencies are gone. What you see is not ringing caused by any filter, imperfect or otherwise. It is exactly what a band-limited square wave looks like.

The fact that the second screen looks like a square wave, means that this DAC has some serious problems. It is reproducing all sorts of ultrasonic garbage that should not be there. The square edges are a symptom of the incaccuracy of this DAC, not proof of accuracy.

Try this: build a 22 kHz high pass filter and connect the outputs of your DACs to it. It should pass virtually nothing. Try to guess what you'll see on your scope with your non-OS DAC with square wave input?"

__________________________________________________ __________________________________________


The scope picture they're talking about (on page 1, first link) is very peculiar, it shows a messed up looking square wave with pre ringing, that is the correctly converted (OS) one, and a fairly decent square wave with no ringing (it's square!) that is the 'badly' converted (DDDAC NOS) one!

Unfortunately you have to log in to see pics there...

The square wave apparently came from a disc, The OS "from the analog output of my cd player". Another poster assumes it was on a disc ("That is because your stimulus signal on the disc was a 'perfect' digital square, not?"), and is not corrected by anyone. It's not explicitly stated beyond that...

Could this be one of the reasons people like the way NOS sounds, despite it's flaws? Can NOS reduce or eliminate pre ringing that is 'built in' to the format? Is this why 'they' insist on compressing the hell out of most recordings?

Just to be clear I am not hearing any fatiguing highs with my DAC. And, it doesn't sound rolled off to me either. As a matter of fact I like the sound of my rig very much. This is why this thread fascinates me. A lot of what I've read has lead me to believe that 1) My system, as much as I like it now, could sound even better with a good quality oversampling DAC (a good thing) and/or 2) my hearing is a lot worse than I would like to believe (not a good thing).

Thanks for the answer.

Isn't it possible to draw a conclusion from a computed comparison of those 20.000 FFT graphs? Could that give a new 'spec' for sound quality or do you think it's irrelevant?

It is possible. It's just that making 20 thousand FFT graphs and then having you go through 20 thousand of them takes quite a bit of time. And honestly probably not worth it. Would you do it again for all combinations of two tones? I think I'd run out of server bandwidth.

You can instead perform a THD+N sweep measurement, and just sort of guess what the FFT would be for each frequency, because most likely it'll have the same harmonics in similar proportion for any given frequency. It's an easier graph to swallow.

But the presumption of roughly the same characteristics across the audible spectrum seems dangerous to me, although I'm sure you're right as well. In this NOS vs OS D/A thing you all got going on here, the discussion has been mostly about the 4 - 15Khz range I think. That's where, somewhere, according to the NOS proclaimers, the wrongdoing of the OS D/A lies.

I'm just curious, because you can discard the NOS lovers like Dan Lavry kind of does, but if you count them in the same group as the tube and vinyl lovers and it's not so insignificant anymore. And those fans are not just consumers, I know from my work that there's also quite a few respected professionals out there that belong to this group. They can't not have a point at all, there has to be something to it that can't be measured right now and I was wondering what direction you'd have to point your scopes at. It can't just be personal preference, that'd be weird I think.

Tubes and vinyl certainly have an effect on the reproduction of sound. And it can be measured. Secrets did an excellent piece on vinyl: Vinyl vs. CD.

BTW, JEJ took FFT measurements at 1kHz and 10kHz of a McIntosh MCD201, and you can see the created harmonics are similar. See part 7. He also states on that page:
It is also true that the same piece may get mastered differently depending on if you purchase it on vinyl or CD. I have heard CDs that were more heavily processed and compressed than their vinyl counterparts, probably because that matches their market segment. I wish I could get the vinyl master on CD for those, because then I'd have the authentic music with the technological superiority of the CD format.

Remember, what people enjoy listening to is not the same as accurate and precise reproduction of sound. Fashion magazines use Photoshop all the time.

Yep, that's very true. It's both a blessing and a curse, but that's such a cliché, it's not even funny. The only problem I have that for some weird reason, to me, that Class A triode or vinyl or NOS(?) sound doesn't sound fake even though it technically is! Maybe it's all down to the recordings, it might very well be

And thanks for the articles, I'm going to read them now.

Just finished reading through this thread. I had dinner after page 10 because I needed a break.

Honestly this is probably the most interesting thread I've read at Head Fi and it also shows what I'm going to call "the Hi Fi problem".

is this why my Valab NOS dac doesn't seem to be able to produce anything over 16k? i know i can definately hear over 16k, it's lovely and painful, but through my valab i get an odd sound going down until about 16k where a high pitch emerges.

gonna run a test now between analogue out form my pc and via the valab...

^ Agree... Lol.

Has anyone taken a scope pic of the output of a NOS dac playing a 1khz signal and compared to an OS dac? The NOS output isnt pretty.

Oh man, someone has woke the sleeping giant.

Since the science wont explain why i prefer a "distorted" sound from tubes rather than the "accurate" solid-state sound, I would choose not to mess with the theory behind all the claims.

Just pick whether suitable to the ears.

There is no sound behind, but there is an explanation to that..