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Inside High-res audio: PCM vs MQA vs CD: 2L Sampler Comparison

amirm

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Another video in this series analyzing objective quality from the label 2L in PCM, MQA and CD. As before, these videos were produced in 2017 although not much has changed since then (other my comment that Amazon did not offer HD content).

 

gvl

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All well designed DACs have some some sort of LPF on the output, and it may start to cut off well before fs/2 for hi-res it being correct or not. How much of that ultrasonic noise is present on the actual DAC output? Paraphrasing you, we don't listen to graphs on the computer screens.
 
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amirm

amirm

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All well designed DACs have some some sort of LPF on the output, and it may start to cut off well before fs/2 for hi-res it being correct or not. How much of that ultrasonic noise is present on the actual DAC output? Paraphrasing you, we don't listen to graphs on the computer screens.
Well before? No. Here is AKM4490:

1620362331165.png


At 96 kHz sampling is only down 6 dB at 48 kHz.

Here is 192 kHz sampling:

1620362410591.png


Bandwidth extends to 105 kHz so even past Nyquist. And that is fast roll off filter. Here is slow:

1620362470155.png


Now you are up to 170 kHz so well past what I am showing.

As I have noted though, there are other costs such as having much larger file to download and store. And in a number of cases paying more for the higher sample rate ones.
 

gvl

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Well before? No. Here is AKM4490

That's digital filter. Isn't there typically an analog LPF as well downstream of the DAC chip? You may not see its effects in-band on 44.1kHz sampling but for hi-res it may cut into that ultrasonic in-band crap, if the filter present anyway. Plus there may be another filter on the amp input. So in reality that ultrasonic noise may be less of an issue than those graphs may suggest which is the worst case scenario, if it ever happens.


pcm1794c.png

akm4490.png
 
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DWPress

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Another affirming video Amir. Money better spent on better speakers.
 
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amirm

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That's digital filter.
No, that is the total filter response. They even show it as a measurement:

1620366921394.png


ADCs often roll off early but DACs go all out and past Nyquist usually.
 

gvl

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No, that is the total filter response. They even show it as a measurement:

View attachment 128432

ADCs often roll off early but DACs go all out and past Nyquist usually.

Measurement of what? Of the DAC chip? The analog LPF is not a part of the DAC chip, it is a part of the overall device, the DAC chip manufacturer can't know what LPF will be used so they can't possibly show that response on their spec sheet. The only way to know is to connect one of your DACs to the AP and check filter response at say 384kHz sampling, and that will be specific to that DAC only. I suspect analog LPF parameters don't change for different sampling rates, in most DACs anyway.
 
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voodooless

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Those analog filters are usually way up there since the digital ones do such a good job already. I think you can practically ignore them.
 
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amirm

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Measurement of what? Of the DAC chip? The analog LPF is not a part of the DAC chip, it is a part of the overall device, the DAC chip manufacturer can't know what LPF will be used so they can't possibly show that response on their spec sheet. The only way to know is to connect one of your DACs to the AP and check filter response at say 384kHz sampling, and that will be specific to that DAC only. I suspect analog LPF parameters don't change for different sampling rates, in most DACs anyway.
You answered your own question in the last sentence. :) ;)

Here is measurement of Topping D30Pro which was handy to grab:

Topping D90 192 kHz Filter Response.png


Basically, everything up to half the sample rate gets through. What you see in my analysis, is what you get out of the DAC.
 

gvl

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Thanks. It's just I remember seeing some DAC measurements showing roll-off earlier than fs/2 on hi-res, not necessarily on ASR.
 
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amirm

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Hi! This videos are very informative! Thanks for all!

I have just downloaded this free tool for linux:

https://www.sonicvisualiser.org/download.html

and I think I've found an ultrasonic pure tone in one of my favorite hi-res tracks. :D
Didn't know about that program. Just downloaded it. It doesn't do DSD unfortunately and uses scientific notation for the frequency but otherwise, definitely does the job.
 

TurbulentCalm

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Very informative videos.It is telling me that there is not much wrong with cd quality, but there is plenty of wrong with the high res files.

I too am finding these posts to be very enlightening.

I’ve been dabbling in the audiophile world for a couple of years and one thing I could shake was the FOMO caused by the belief that ‘Hi-Res’ audio would add to the quality of the audio I was listening to.

@amirm has killed this fear with just these three fantastic reviews.

Given that I’ve never heard a single track in ‘Hi-Res’ that I sounded in anyway better than 16/44.1, I’m now not just happy to stick with CD quality.
M
 

xaviescacs

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Didn't know about that program. Just downloaded it. It doesn't do DSD unfortunately and uses scientific notation for the frequency but otherwise, definitely does the job.

I didn't notice the DSD issue. Actually, I don't have any DSD file. Here is my first analysis.

audio_spectrum.png


This is really very rewarding to me, as with some background knowledge on mathematical transformations and the recent videos on ASR, I'm able to assess to some extend the quality of what I'm purchasing.
 
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