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Digital Audio and Amplifier Noise Floor Comparison - Is 16bit/44.1kHz All We Need ???


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4 minutes ago, psjug said:

 

Best measuring amplifier you can find is the same as "most equipment"?

 

You are welcome to pick anything you want to measure by.  All I said was that 24bit is below the noise floor of most equipment, and 16bit is above same. Exactly how much is dependent upon equipment chosen, but in general, that holds true. 

 

I am unclear exactly what your objection is. Here are a couple other amps. 

 

The now $379 Outlaw Audio M2200 amp is 112db A weighted, and still falls within that criteria. 

The $1700  Peachtree Nova 150 I use a lot is 105db A weighted. 

 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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31 minutes ago, psjug said:

I just thought it was interesting that you used spec from the Benchmark amplifier which was about where you said ordinary equipment should measure.

 

As for your own amplifier, the A weighting is likely to be giving a big improvement in the spec since it's a class D amplifier.  Not to be down on your amp, just to point out what is realistic.  If you don't care about the A-weighting of the amp spec, then you shouldn't care about noise shaping with 16 bit to get much better SNR.

 

Edit: In other words, I suggest that if you are using A-weighted spec to try to match equipment to 16-bit audio, then you should use the effective SNR for dithered 16-bit, so something like 115 to 120 dB.

 

A weighted specs are often all that is easily available, but that is a good point. What would you suggest are figures you would be happier with? I generally prefer A weighted specs myself.

 

However,  it does not follow that noise shaping to boost the 16bit noise floor is the same thing, or even related. I think you are conflating two different subjects there.

 

That boost to 120db in 16bit PCM by “noise shaping” has other costs. Depending upon the exact scheme, you get degradations in coherency and an unstable noise floor. Techniques commonly used to restore that, such as windowing, can boost the amplitude of some frequencies and have other effects. 

 

In short, you are hearing a significantly modified sound, whereas those issues do not exist if you simply move to 24bit. I find it rather silly to defend 16 bit recording, once you take that into account. 

 

[Edit - perhaps you could be a little more clear on the technical point you are trying to make? ]

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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9 minutes ago, tmtomh said:

 

There are multiple ways to measure a noise floor - the traditional SNR as noted above, and the THD-N/SINAD as I'd noted previously.

 

Moreover, the effective noise floor of CD is -120dB with noise-shaping dither.

 

I'm really not trying to win an argument for the sake of winning an argument. My point simply is that one has to go to some lengths to put together an equipment chain that can top the effective noise floor of a properly produced 16-bit CD/digital file, and therefore it's not accurate that 16-bit's noise floor is generally above that of most equipment, even most decent equipment.

 

I am hopeful that in the future, the specs of the very best Hypex-based amps like the Benchmark, along with the specs of the very best DACs, will become more common, especially in more affordable equipment. But for now, the majority of amps and DACs don't have noise floors that reliably or significantly exceed that of properly dithered 16-bit sources. (And that's putting aside the fact that it's almost impossible to be in a practical listening space where a -96dB signal can be heard when the volume level is set so that peaks are not at ear-damaging levels.)

 

Where we disagree is that 16 bit noise floors are below the noise floor of most equipment. I think you are simply wrong there, 16bit is well above the noise floor for most equipment these days.  And of course 16bit noise shaping adds some peculiar distortions not present at all in 24bit.

 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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27 minutes ago, esldude said:

A-wtd is usually a 4-6 db improvement over no weighting.  So it isn't like unweighted results are suddenly terrible.  More common is fudging on real values or some trickery in gain staging that gives a number you won't see in normal use.  As Rt66indierock said, your noise floor is much closer to the signal at 1 watt levels.  Of course with common speakers you only need mid-80 db SNR to be so low it will never be heard at 1 watt.  Plus your SNR with dithered 16 bit is worse by a half bit to bit.  So rather pointless to engage in petty arguments without putting all this in context. 

 

I've found it interesting no one ever points out that with shaped dither and 16 bit audio there is a real benefit to high sample rates.  Here is where I took silence, and saved it in 16 bit with shaped dither in both 44/16 and 192/16.  I then filtered out everything above 20 khz in the 192 file.  Notice the shaped 44 has a noise level of -84 db while the filtered 192 is -120 db.  This is what would happen if your speakers (and your ears) don't respond above 20 khz.  Of course no one does 192 at 16 bit do they.  Getting back on topic, something like this could have been done with MQA without requiring licensing, messing with undecoded fidelity or causing other problems.  

 

image.thumb.png.c044ec0125a9c1be6a0ab0ac2892cd97.png

 

Well said. Did you get the typical “bathtub” output? 

 

I just find find it hard to argue that 16bit, even with noise shaping is preferable to 24 bit. Equipment specs are only going to keep getting better and better. 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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10 minutes ago, Rt66indierock said:

 

In my defense, I'm going to keep using my Klipsch Heresy's at home so I need something quiet. John Siau of Benchmark recently wrote and made some graphs about how quiet your stuff has to be to hear certain bit depths. 

 

Those are really efficient aren’t they? The IIIs are like 99db. Generally the more efficient the speaker, the quieter the electronics of course. 

 

P.S. What defense? I don’t think many reasonable people would say those Heresy speakers are not well worth their keep.  If they do, ignore ‘em. 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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1 hour ago, psjug said:

Just out of curiosity, have you or @Shadders seen measurements of finished amplifiers made from these kinds of kits?  I'm not sure I've seen measurements of any amplifier other than the AHB2 that meets the 96dB THD+N at 1W.  Maybe nCore is right on the edge of meeting this with a 22KHz filter.  Maybe there are a few others, but I bet they are rare.

 

It is also interesting that one would pick THD+N when choosing to compare against the noise level of a digital signal.  Perhaps it would be good to very briefly make sure we are all on the same page here regarding what we are talking about. 

 

As far as I know, most ADCs have a voltage range of plus/minus 10V. A 16bit device has 2^16 (65536) possible values, which means a resolution of 20/65536, or 0.3mV.   That means the dynamic range in decibels would be  20 LOG10  (65536)  which equals 96dB. In other words, the absolute noise floor of a 16bit device can never exceed -96dB.  It will never reach -96dB either, as there is electronics noise to measure. Commonly, 16bit devices like CD players have a much lower noise floor.  (I didn't go look them up, but if you do, be aware, most oversample before they hit the onboard DAC. You have to measure off their SPDIF outputs, and that doesn't always work either.) 

 

Now a 24 bit system never really hits 24bit resolution of course, but by the same maths as above, it's absolute noise floor would be -144dB. It's actual noise floor will be even lower than that due to electronics noise and such. 

 

And using just a little bit of that common sense, we can say the noise floor of any system will be limited but the highest noise floor of any electronic component in the chain. All of which says that THD+N is a good measure. Right? 

 

So, in comparing a 16 bit system - to compare apples to apples - you really need to look at components that exceed the noise floor, as measured by THD+N of the digital system. Not as may be happening here, by comparing the THD+N of an amp to the theoretical maximum noise floor of the digital system. 

 

Everyone agree?  If so, then getting the THD+N of the digital systems is important, and honestly, I don't have those. I would expect 20dB to be a reasonable figure, as suggested, so for 16 bit systems, you are looking for electronics quieter than about -76dB. For 24bit systems, perhaps a bit larger difference, say, 35dB, or around -109db. You can of course, play with those figures, but I think that hits the ballpark. And that may change your thinking on 16 bit systems a bit. Or not, as you will.  But amps that exceed the actual noise floor - how so ever you may measure it - for 16 bit systems seem to be pretty common. 

 

Also, so far as I know, most companies measure distortion over the entire Nyquist range using 2.3V shorted. At least, respectable manufacturers of high end audio gear do these days. That was so uncommon before, it is is good to be suspicious of it.  

 

The upshot of all that is that I firmly believe that 16bit audio covers most of the dynamic range of a recording, but that 24bit covers it all, with a bit of room to spare. Does that mean CDs don't sound great? Of course not, they do. But if I have the choice, I will also choose a 24bit high sample rate file for my archive. Always given of course, that the file is actually that, and not a upsampled 16/44.1k source - or worse. :)

 

-Paul 

 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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5 minutes ago, Rt66indierock said:

 

My Heresy II speakers are 96 dB so I need a little more.

 

Those are measures of efficiency.  Your Heresy's only require roughly 1/10th the power to reach the same sound levels as a speaker with 86db efficiency. 

 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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1 hour ago, Rt66indierock said:

 

My Heresy's hiss a little with an amp that is quiet with the speakers in my office that are approximately 86 dB efficiency.  

 

You probably need a little quieter amp for those guys, unless you only hear hiss while there is silence within a track.  They are very sensitive little champs. In comparison, my desktop monitors are 83.5dB/2.83v/m.  It takes a lot more power to drive them up to high SPLs, but it takes a really noisy amp to get them to hiss. 

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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Perhaps all we need for playback, even ignoring headphones. :)

 

But a lot of folks, myself included, do not buy into “perfect sound forever” from 16/44.1. Certainly not for recording, and actually not for playback, since most 16/44.1 DACs are not playing that bit perfect, but are oversampling anyway.  

 

So, if the DAC is forced to oversample to sound good, using zero and hold or whatever scheme you choose, does it not make sense to just provide the DAC with a higher sample rate and avoid all the upsampling and SRC in the first place? Storage space and network transmission is a non-issue to most audiophiles in 2019, so that is far from a compelling reason to continue with 16/44.1k. 

 

And yes, current systems and technology may have limits, but that does not mean tomorrow’s tech will have the same limits. So it makes a lot of sense to save the music we have in the highest possible quality format. It makes even more sense too have multiple copies of that music spread around to help ensure its survival through the next fire. 

 

So no, 16/44.1 is not good enough. Unless of course, it is all that is available for some music I really love. Then yep. But of course, I will keep that music in its redbook form, not archive it as MP3 or some other 3 letter format.  

Anyone who considers protocol unimportant has never dealt with a cat DAC.

Robert A. Heinlein

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