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Old 3rd March 2011, 03:38 PM   #21
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That will certainly work. Now you need the fiber cable with the correct ends.
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Old 3rd March 2011, 03:52 PM   #22
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I'd kept on seeing this 'NOS' DAC thing being referred to, and wondering why 'new old stock'... Now I understand! Non-oversampled. Next it will be that only R-2R resistor ladders are acceptable, and then finally that only weighted resistor summers (like I knocked together many years ago) give the suitably 'musical' sound.

On the other hand, I have an irrational phobia of Class D amps, so maybe I shouldn't be so dismissive of these fads.
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Old 3rd March 2011, 04:15 PM   #23
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Quote:
Originally Posted by CopperTop View Post
I'd kept on seeing this 'NOS' DAC thing being referred to, and wondering why 'new old stock'... Now I understand! Non-oversampled. Next it will be that only R-2R resistor ladders are acceptable, and then finally that only weighted resistor summers (like I knocked together many years ago) give the suitably 'musical' sound.

On the other hand, I have an irrational phobia of Class D amps, so maybe I shouldn't be so dismissive of these fads.
I wonder though, have you yet had the opportunity to listen to a decent NOS DAC at your leisure? If so, what did your ears tell you about it's 'musicality', as compared with oversampled playback?
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Old 3rd March 2011, 04:17 PM   #24
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Yes, it took me a while to work that out too. Then I read up on NOS DACs, and realised that although they apparently sound OK they are 'wrong' and widely misunderstood by their fans. Having said that, I bought a cheap one off ebay and intend to play with it.
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Old 3rd March 2011, 04:38 PM   #25
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Quote:
widely misunderstood by their fans
LOL.

NOS DAC fan to audio buddy : "It sounds absolutely wonderful". Audio buddy to fan: "You are wrong!"
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Old 3rd March 2011, 05:46 PM   #26
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Yes, it took me a while to work that out too. Then I read up on NOS DACs, and realised that although they apparently sound OK they are 'wrong' and widely misunderstood by their fans. Having said that, I bought a cheap one off ebay and intend to play with it.
You may be in for an ear-opening listening experience. My ears tell me that while Shannon and Nyquist are fine for digital communication systems, they don't hold sway for the digital-music human listening experience. The one flaw you will likely quickly notice is the well known sample-and-hold based -3.16dB frequency roll-off. This can be corrected with a rather simple analog EQ circuit, as Thorsten Loesch is quick to point out. The ease and clarity (particularly apparent on orchestral crescendos) of NOS should be immediately audible, but once equalized flat, you won't go back.
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Last edited by Ken Newton; 3rd March 2011 at 05:53 PM.
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Old 4th March 2011, 10:28 AM   #27
DF96 is offline DF96  England
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Quote:
NOS DAC fan to audio buddy : "It sounds absolutely wonderful". Audio buddy to fan: "You are wrong!"
You weren't paying attention. I said "misunderstood", not "misheard". NOS DACs may sound OK, but not for the reasons often claimed for them (which are usually based on misunderstandings about sampling, brick-wall filters etc.).

The snag with simple NOS DAC is the HF loss. Correcting this messes up the phase response, but hopefully not too audibly.
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Old 6th March 2011, 04:29 AM   #28
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Hello

A NOS dac will have a lot of HF noise at the sampling frequency, and above. This noise will create IM distortion going down to audible frequencies. It's the main reason of the lack of precision in complex (orchestral, heavy rock) music.

That mosly why NOS dac need an excellent low pass output filter to cut that hf noise, but that filter will bring phase shift.

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Gaetan

Last edited by gaetan8888; 6th March 2011 at 04:36 AM.
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Old 6th March 2011, 02:51 PM   #29
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Gaetan:

That's an interesting observation - a lack of precision on complex music via NOS. Could you further describe what you believe you are hearing?

As far as intermodulation products are concerned, they are not automatic and depend on the linearity of the succeeding analog stages. Intermodulation is produced by non-linearity, a linear stage of sufficient bandwidth will not produce intermodulation products.
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Last edited by Ken Newton; 6th March 2011 at 02:56 PM.
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Old 6th March 2011, 03:12 PM   #30
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An unfiltered NOS DAC (which is the majority of NOS DACs?) generates ultrasonic images of audio signals. For the higher frequency audio, the image will be at a similar level to the music; for LF audio it will be at a lower level. It will not be directly audible but it could intermodulate.

My guess is that solid-state amps will suffer worse than valve amps, because they are usually intrinsically less linear and rely more on NFB - but NFB reduces at higher frequencies so the early stages of the amp will be presented with a high level signal and no NFB to counteract it. However, many amps start with a low-pass filter so if this has a sufficiently low corner frequency (low enough to frighten some audiophiles) it will help.
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