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Quality aspects of ADC, Does quality gear makes a difference?
ktf
post Mar 3 2011, 22:45
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Hi all!

Background information (safe to skip rolleyes.gif )
Currently I'm preparing a large archival operation: my musical society has a collection of recordings on compact cassettes from 1980 to 1990, about 140, which I think have to be digitalized to protect them from deteriorating. I have found a nice tape deck (Nakamichi DR-3) but it has to stay at the office of the executive committee. A friend of mine has a nice ADC for this job, a quality portable mixing console with USB out, but it cannot stay at the office as it is more or less public and he doesn't trust everyone there. However, it is too much hassle to bring it every time, as I think this operation will cost about a year: 3 recordings a week. So, I guess I'm stuck with my own ADC: a Creative X-Fi Surround 5.1 USB-card, which is not really made for the job, but I can at least leave it at the office, as it isn't that valuable.

On-topic
That friend of mine that offered me his portable mixing-console with ADC argued that with a cheap ADC all little nuances and details would vanish, so I should look for another solution than using my Creative ADC. That made me think: i'm much more a theoretician than he is, so I was wondering, what makes a high quality ADC? I know the working principle of several ADCs, I can't imagine which link in the chain would be capable of 'erasing details' anyway. How does a non-linearity in an ADC sounds like in practice? And jitter? I guess uncorrelated, random jitter could sound like 'more noise', as it is random. To me it seems a low-quality ADC doesn't add anything but noise and a non-linearity, let alone it could remove things from the signal.

In short: what could a low-quality ADC do with the signal except adding noise? Probably I'm far too short sighted, can anyone enlighten me?


--------------------
Music: sounds arranged such that they construct feelings.
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DVDdoug
post Mar 3 2011, 23:52
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The only thing I'd even consider is noise. And, unless the ADC/soundcard is defective the noise will be very low compared to the background noise on the cassette tape. Most soundcards are superior to cassette in frequency response & distortion.

Probably the most important thing is to get your recording levels right. You want a strong enough signal so that the ADC noise remains insignificant, but you don't want to clip (distort) the ADC either.

If altering the sound doesn't violate any archiving principals, you might be able to use some digital noise reduction and/or EQ to make the digital copy sound better than the analog cassette! Or, you can keep both an unaltered archive and an enhanced version (something I've done). Just beware that noise reduction can introduce artifacts (depending on the source material) and of course any EQ "improvements" involve of taste & judgment.

I have no idea what jitter sounds like... I've never heard it. From what I understand, the amount of jitter in any normally operating device is inaudible. ... You have to intentionally design something with gross jitter before it becomes an issue.

If someone starts giving you a bunch of nonsense about jitter, or "high resolution" audio", or "nuance", Ethan Winer's website has a lot of useful information to bring you back to reality.

P.S.
When it comes to timing-related issues, I be more concerned about the analog side... Tape speed, wow & flutter, stretched tape, etc. These are likely to be at least 10x worse than digital jitter. But again, I've never heard any speed/timing problems from any properly working turntable or tape machine. (I have heard these kinds of defects when the unit had a worn belt, or something was bent, etc.)

This post has been edited by DVDdoug: Mar 4 2011, 00:10
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Posts in this topic
- ktf   Quality aspects of ADC   Mar 3 2011, 22:45
- - DVDdoug   The only thing I'd even consider is noise. A...   Mar 3 2011, 23:52
|- - ktf   QUOTE (DVDdoug @ Mar 3 2011, 23:52) The o...   Mar 4 2011, 16:19
- - DonP   One thing that's been an issue in the past is ...   Mar 4 2011, 17:08
- - DVDdoug   QUOTE So, the THD+N (for distortion and non-linear...   Mar 4 2011, 20:51
|- - ktf   QUOTE (DVDdoug @ Mar 4 2011, 20:51) With ...   Mar 4 2011, 23:42
|- - Notat   QUOTE (ktf @ Mar 4 2011, 16:42) It also r...   Apr 5 2011, 15:18
|- - ktf   QUOTE (Notat @ Apr 5 2011, 15:18) Apologi...   Apr 5 2011, 15:23
|- - Notat   In your setup, there are two ground paths between ...   Apr 5 2011, 18:49
|- - Arnold B. Krueger   QUOTE (Notat @ Apr 5 2011, 13:49) In your...   Apr 6 2011, 14:37
- - Arnold B. Krueger   QUOTE (ktf @ Mar 3 2011, 16:45) That frie...   Mar 8 2011, 13:38
|- - ktf   QUOTE (Arnold B. Krueger @ Mar 8 2011, 13...   Mar 8 2011, 18:02
|- - Arnold B. Krueger   QUOTE (ktf @ Mar 8 2011, 12:02) QUOTE (Ar...   Mar 8 2011, 19:09
|- - ktf   QUOTE (Arnold B. Krueger @ Mar 8 2011, 19...   Mar 8 2011, 21:25
||- - Arnold B. Krueger   QUOTE (ktf @ Mar 8 2011, 15:25) QUOTE (Ar...   Mar 8 2011, 22:59
||- - mixminus1   QUOTE (Arnold B. Krueger @ Mar 8 2011, 13...   Mar 8 2011, 23:17
|- - Kees de Visser   QUOTE (Arnold B. Krueger @ Mar 8 2011, 20...   Mar 15 2011, 13:34
|- - Arnold B. Krueger   QUOTE (Kees de Visser @ Mar 15 2011, 08:3...   Mar 24 2011, 12:32
|- - DonP   QUOTE (Arnold B. Krueger @ Mar 24 2011, 06...   Mar 24 2011, 12:53
- - ktf   QUOTE (Arnold B. Krueger @ Mar 8 2011, 22...   Mar 13 2011, 22:49
- - ktf   Today I made some recordings which made me wonder ...   Mar 22 2011, 21:56
|- - Arnold B. Krueger   QUOTE (ktf @ Mar 22 2011, 16:56) I usuall...   Mar 24 2011, 12:51
|- - ktf   Woops, I forgot about this topic. I have set track...   Apr 5 2011, 10:19
- - 2Bdecided   Cleaning and demagnetising the heads, matching the...   Apr 6 2011, 15:14
- - Arnold B. Krueger   QUOTE (ktf @ Mar 3 2011, 17:45) Hi all...   Jun 6 2012, 13:20


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