What do you think makes NOS sound different?

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#1,886
lcsaszar said:
If my amplifier and my tweeter can't reproduce US and I can't hear US, how can US sidebands be accounted for NOS/OS difference?
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That was essentially the founding postulate of this thread. As was later logically deduced, ultrasonic intermodulation was not the cause of the subjective difference between OS/NOS, because that difference remained even after the ultrasonic image-bands had been filtered in analog. Suppressed ultrasonic image-bands equals suppressed resulting intermodulation products.

What we weren’t certain of back then was whether or not ultrasound could generate acoustic intermodulation within the ear. Was this a real auditory phenomena or not? During our investigation, I wasn’t aware of the 2018 Havana Syndrome paper posted I just posted. That paper asserts that acoustic intermodulation of ultrasound is a real phenomena.
 
#1,887
Ken Newton said:
Yep, I sure do. I hope that someone has a logical technical explanation.

As for the acronym, NOS. While it may be a bit in-artful, I think its commonly understood to signify a DAC without an FIR interpolation filter. Leaving the D/A output as an un-reconstructed signal. Either retaining it's image bands, or somewhat suppressing them post D/A conversion in the analog domain.
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In much of the online world NOS means New Old Stock and is particularly relevant to valve enthusiasts and of course there are many of those on this forum.
 
#1,889
I'd like see your comment on one aspect of filtering. There is a tutorial for dummies, it seems taken from the 20 years old marketing material (when half-band filters were common), but it is not an issue. An author, dCS rep says that we should chose our DAC filter to match a filter used in ADC during recording. Any comment related to our tests using PGGB?

Quote related to a filter in dCS 904:
The final filter is around 100 taps long, meaning that effectively there is little to be gained from using a much longer filter on replay (inside the DAC)
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And a more general note:
What this stands to show is that with digital filter design, the signal chain as a whole needs to be considered, as opposed to just the DAC in isolation. DAC filters which are likely to work well with realistic ADC filters are ideal – in reality the use of a filter which is either not present, too short or too long in a DAC can have detrimental effects. Filter length of course must be balanced with the other factors described above, which is where good engineering comes into play – understanding how to employ the necessary trade-offs to create a set of filters which work well regardless of what content is thrown at it. This is the reason a dCS DAC has so many filters to choose from – the DAC doesn’t (and can’t) know the filters which were used to create the signal, so several options allow the user to achieve the best musical experience irrespective of source material.
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Full text: dCS Ring DAC - A Technical Explanation | Page 11 | Headphone Reviews and Discussion - Head-Fi.org

More filters, more headake, NOS rules. 🙂
 
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#1,890
In the message you linked to, a zeroth-order hold as used in NOS DACs is the first example of poor reconstruction filtering.

I don't follow the line of reasoning regarding long reconstruction filters. If you want the DAC to filter of aliases caused by a too wide ADC anti-alias filter, it is more effective to use a long filter with a cut-off frequency just below the start of the frequency range that has aliases than to use a short filter.
 
#1,891
sajunky said:
I'd like see your comment on one aspect of filtering. There is a tutorial for dummies, it seems taken from the 20 years old marketing material (when half-band filters were common).
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It must indeed be dated information from when little was known what effect ripple and echo’s could have on sound perception.
We have seen the opposite in this thead’s tests, the longer the better, haven’t we?

When there’s one company who knows how to make a perfect sounding DAC it is dCS.

Hans
 
#1,892
"When there’s one company who knows how to make a perfect sounding DAC it is dCS."

Not according to everyone's opinion. There is a reviewer that owns a top of the line dCS and Chord DAVE. Privately he uses the DAVE. Publicly he has to say the dCS is best. He is after all a reviewer.
 
#1,894
You are taking my words out of their context and shooting from the hip.
I didn’t say they are better than the rest or being the only ones making good DAC’s.
They, as a company striving to play in the top league, must very well know that 100 taps are not enough for a perfect reconstruction filter.

Hans
 
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