Aliasing Intermodulation Distortion and filterless DACs - diyAudio
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Old 24th November 2002, 08:10 PM   #1
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Lightbulb Aliasing Intermodulation Distortion and filterless DACs

Can somebody even try to explain to my simple brain, why many non-digital filtering DACs sound so good even though probably account the most for one of the theoretically most easily audible artifacts in DAC performance: intermodulation distortion.

A DAC that does not do any filtering beyond 20 kHz will help ultrasonic frequencies to form (when used with most speakers) intermodulation components in the audible range.

This, as I understand, should sound very nasty, considering how sensitive human hearing is to intermodulation distortion (in general, of course there is masking).

I'm not trying to put down any approach or to claim somethign silly like, filterless DACs can't work.

I'm just interested, whether anybody has a working theory on why we hear what we hear, although measurements and theory might suggest otherwise.

Also, please note that I'm trying to confine my question only to intermodulation distortion in speakers in regard to DAC operation at high frequencies.

Comments?

regards,
Halcyon

PS I've used the search, but couldn't find specific issues relating to this. If I didn't search properly, I do appreciate links as well. Thanks.
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Old 24th November 2002, 08:53 PM   #2
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Wink NON-OS DAC's

Hi halcyon,
In my experience a digital filterless DAC sounds better with analog low-pass filtering applied. Probably due to the intermodulation effect you described. The <B><I>technical</B> </I>problem is how to filter and pass the audioband as much unharmed as possible. I also did not like the sharp staircase signal on top of a 3150 sine signal. I wanted it smoooth. Despite NON-OS concept DAC's do sound very different from each other. I have tried AD1851N-J, AD1864-J, AD1865N-J, AD1865N-K , TDA1541AS1, TDA1543, TDA1545, all NON-OS. And the winner is.....?
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Old 25th November 2002, 08:24 PM   #3
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Does that mean you are still looking?

Or all of the above have their pros and cons?
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Old 26th November 2002, 07:12 AM   #4
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Lower sensitivity to jitter is my guess. Plus, that SAA7220 is the main reason I hate the TDA1541 so much.

Jocko
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Old 26th November 2002, 08:18 AM   #5
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Default jocko...

hi there,

have you ever listened to a NOS dac ?
and if, how was it ?

best regards,
troels
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Old 28th November 2002, 04:58 AM   #6
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Sounds better than it ought to. Just because I don't like them is no reason not try one. I just don't see any advancement in this approach. My background is research.......so I like research.

Jocko
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Old 29th November 2002, 12:35 AM   #7
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Cmon Jocko, "not liking them" and "liking research" can't be happily married in one post.
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Old 29th November 2002, 03:29 AM   #8
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Probably these HF potential IMD components can be heavily affected by shielding, connectors, interconnects, source and destination components, phases of the moon, etc. So if nothing else they provide a much more variable sound across different setups, keeping tweakers busy for years. ^_^
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Old 29th November 2002, 08:49 AM   #9
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Halcyon,

I think that whatever theory comes up the practical result is what counts isn't it ? The explanation you want is the explanation the builders of non os DAC's want to learn too.
To my simple brain the lower sensitivity to jitter counts for a great deal in the results

Please see this interview what Kusonoki has to say about digital filters: http://www.tnt-audio.com/intervis/kusunoki_e.html
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Old 29th November 2002, 02:44 PM   #10
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Quote:
Originally posted by tiroth
Probably these HF potential IMD components can be heavily affected by shielding, connectors, interconnects, source and destination components, phases of the moon, etc. So if nothing else they provide a much more variable sound across different setups, keeping tweakers busy for years. ^_^
What makes you say this?

Have you actually tested various filters and their audible effects on AID with loudspeakers?

That is, not just looking at thing in an oscilloscope?

Mr Black (the author of AID article) seems to have done his homework and even his old ears can hear the intermpodulation components.

Why do you think that moon phase, cabling and other issues you mention are somehow comparable in audibility?

Have you actually listened experimentally for the differences in moon phases to audio quality?

I wish that people were not so eager to ridicule other people's sincere work, unless they have some experimental results that absolutely prove the opposite and that they think that the situation calls for humor.

Sarcasm is the most shallow of the intellectual traps, IMHO.

regards,
Halcyon

PS I think A LOT of the stuff on this forum is A) self-righteous mockery by people who have not tried it themselves, B) pseudo-theoretical "can't be true, because text book say so" arguments. I'm guilty of this myself often. I hope you are not
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