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Why do NOS dacs sound different to oversampling designs?

Purité Audio

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#1
As per thread title, I have read that there is no reason they should in a completely linear system, if such a thing exists of course.
But whenever you look at the measurements of a classic NOS design they do, please explain.
Keith.
 

Opus111

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#2
There's rather a variety of NOS DACs so it would help if you'd pin down one and describe how it sounds different to another DAC (specified).
 

Purité Audio

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#3
JA's measurements of the Zanden 5000, which I believe is a classic NOS design.
I will post a link.
Keith.
 

Opus111

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#4
Its a classic NOS (with TDA1541) but definitely not a mainstream one as it comes with a passive output filter. Most NOS DACs on the market don't have anti-imaging filters.
 

Purité Audio

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#6
I thought by definition a non over sampling DAC could not have a reconstruction filter?
Keith.
 

dallasjustice

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#7
I've owned the totaldac which does have a gentle anti-aliasing filter. I think the big attraction to these types of DACs is the HF roll off. For those who are familiar with DSP target curves, almost every listener prefers a slowly rolled off HF starting around 1khz. These DACs do just that. That's why they are so popular, IMO.

For me, I'd rather have accurate gear and later tailor my target curve according to my preference in my room.
 

amirm

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#8
I thought by definition a non over sampling DAC could not have a reconstruction filter?
Keith.
Non over-sampling means the old fashioned DACs that were 16 bit converters running at the sample rate of CD. These were used in first generation CD players and were followed by analog reconstruction filters. At least that is my understanding of it.

I also understand that people take these DACs and run them "open" with no reconstruction filter.

Has it become commonplace to have these DACs run without a filter? I just not in the DIY circle to know :).
 

Blumlein 88

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#9
Non over-sampling means the old fashioned DACs that were 16 bit converters running at the sample rate of CD. These were used in first generation CD players and were followed by analog reconstruction filters. At least that is my understanding of it.

I also understand that people take these DACs and run them "open" with no reconstruction filter.

Has it become commonplace to have these DACs run without a filter? I just not in the DIY circle to know :).
It is not universal, it is however common to go sans filtering. Makes for better square wave response in the old sample and hold regime. You also can get aliasing and such. You basically are letting your speakers and ears do the filtering that was left off. Since it works as well as it does, it actually is a good data point that people don't hear ultrasonics.

Then as dallasjustice says some have a slow roll off filter which usually rolls upper-midrange and above gently. So they aren't all the same.
 

Opus111

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#12
I thought by definition a non over sampling DAC could not have a reconstruction filter?
That has been the tradition for NOS DACs, but its not any kind of definition. The reconstruction (or anti-imaging) filter needs to be rather sharp when oversampling's not used, that's one reason its been omitted. Sharp filters tend to be complex and rather sensitive to component variation.
 

Opus111

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#14
I think the big attraction to these types of DACs is the HF roll off. For those who are familiar with DSP target curves, almost every listener prefers a slowly rolled off HF starting around 1khz. These DACs do just that. That's why they are so popular, IMO.
Sounds like you may have been influenced by Bruno - that's been his position. I think he even did an experiment with another DAC (non-NOS) where he applied the same roll-off (maybe digitally?) and got the same approval from a test subject as for a NOS DAC.

However I've corrected my NOS DACs' roll-offs using various methods and their aural attractiveness merely increases.
 

amirm

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#15
In the spirit of the Hydrogen Audio forum, doesn't someone first have to prove with blind tests that the DACs in question actually do sound different? Why worry about differences that may not be real?

--Ethan
In absence of that data, I am open to investigating the technical merit, measurements, etc.

What is a cheap example of this this type of DAC should I be inclined to get one?
 

Opus111

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#16
Something with a TDA1543 will probably be the cheapest, and these have particularly lousy measurements, especially low-level linearity. Type 'TDA1543 DAC' into eBay or Aliexpress and see what shows up.
 

Purité Audio

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#20
Can we agree on a definition of a Non oversampling design, there appear to be so many variations.
I would like to understand whether the treble droop is inherent or merely a design decision.
If one chooses not to use a reconstruction filter, will images fold back into the audible spectrum.
I will try and find some variations and their measured behaviour.
Keith.
 
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