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Old 12th February 2003, 02:21 PM   #1
Bill F. is offline Bill F.  United States
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Default Hard drive vs. CD playback

A couple questions for you digital folk:

1) In terms of signal integrity, jitter, etc., how does hard-disk playback stack up to a decent CD transport? (Let's assume the HD playback is redbook coming from an average PC under light CPU load running Windows XP and outputting digitally without resampling through a decent digital sound card.)

2) Are there sonic advantages to upsampling redbook and outputting through a 24/96 DAC? Are there upsampling programs that smooth the waveform (like clipped peak restoration on a small scale)?

The reason I ask these questions is that I'm trying to imagine a somewhat future-proof digital playback system and some way to squeeze extra mileage from my CD collection as technology marches on.

Thanks,

Bill
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Old 13th February 2003, 12:34 PM   #2
DRC is offline DRC  United Kingdom
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Bill,
[1] Jitter will only be as good as the soundcard you use. The soundcard will *probably* have a sizeable cache - as long as the PC's operating system (or MS windows if you don't have one ) can stop this cache underflowing it should be OK. The internal PCI bus / HD will have no trouble with this quanity of data (I have 32 bit video across PCI bus on my PC) Are you thinking of an external DAC, as 24/96 may not be available as a digital output.

[2] You can recreate information that is not there but interpolation to a higher sampling frequency can make the subsiquent analogue filtering easier. Still only as good as the soundcard and the interpolation algorithm it uses (upsampling). I would think any fancy interpolation / smoothing / fixing up might best be done in advance of playback, using the PC to do the work and feeding 24/96 straight into the soundcard. I have been thinking of doing this myself, once i have a suitable DAC.

Dave
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Old 13th February 2003, 04:36 PM   #3
Bill F. is offline Bill F.  United States
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Thanks for the reply, Dave.

Yes, I'm picturing a 24/96 digital signal (S/PDIF?) out to an external DAC.

Pardon my ignorance, but is jitter still soundcard-dependant when the card is just passing a digital signal to an external DAC?

My idea is to rip my CDs to .wav files, use some mysterious software ap (Does such exist?) to upsample/interpolate/smooth waveforms, resave at 24/96, and play back from the hard drive through an external DAC.

Do you think this would be a worthwhile endeavor that would squeeze a little more life out of my CD collection, thus bridging the gap somewhat to HD formats (and/or maybe provide a slightly more "analog" flavor)?
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Old 13th February 2003, 08:55 PM   #4
DRC is offline DRC  United Kingdom
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Bill,
Quote:
Pardon my ignorance, but is jitter still soundcard-dependant when the card is just passing a digital signal to an external DAC?
This may depend on the DAC. DACs (IIRC) derive the conversion clock from the SPDIF input data clock and unless the DAC does some buffering / reclocking the jitter will mess up conversion timing.

Quote:
My idea is to rip my CDs to .wav files, use some mysterious software ap (Does such exist?) to upsample/interpolate/smooth waveforms, resave at 24/96, and play back from the hard drive through an external DAC.
I guess there will be commercial software available, probably expensive though.
I am planning to use open-source or write my own - probably starting with some 16/44 -> 16/44 *enhancement* as I already have herdware for this . I have not researched open-source tools yet.

Quote:
Do you think this would be a worthwhile endeavor that would squeeze a little more life out of my CD collection, thus bridging the gap somewhat to HD formats (and/or maybe provide a slightly more "analog" flavor)?
(I think)

Dave
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Old 14th February 2003, 08:46 AM   #5
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Default Hard Drive vs. CD Playback

Hi,
I'm interested in carrying out some development on PC based "interpolators". I do C and c++ programming on linux systems though there is no reason why the interpolation "engine" shouldn't run on Windows as all it will do is open a file, operate on the bit stream and send the data to the sound card. I fancied the Perpetual Technologies beasties when they first came out but it seems a bit dear to spend nearly $2000 to carry on listening to what we've already got. The first questions are what hardware would be developed for - the M-Audio 24/96 cards are supposed to be good but what 24/96 converters are out there that re-align the digital stream ("reclock") and are cheapish? For the more mathematically inclined how many "operations" could be carried out at 24/96 by a "standard" PC?
Bill
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Old 14th February 2003, 12:42 PM   #6
DRC is offline DRC  United Kingdom
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Quote:
BillyBoy wrote:
For the more mathematically inclined how many "operations" could be carried out at 24/96 by a "standard" PC?
This doesn't need to be done in real time so the limit depend on how long you want to spend processing it. My experience, with modern PC's, is that their numeric processing capabilities are simply awesome, given well designed software (don't be fooled by that dog-slow user interface).

For example :-
16/44=10MB/min
24/96=34MB/min
A machine with 1GB main memory could upsample/filter a 10 min track in memory !
At $150 a 60G HD could store 1800 minutes at 24/96 = 35+ disks worth !

The only down side I see is the recording industry going flat out to stop us

Dave
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