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Old 20th September 2003, 07:48 PM   #1
tmd1 is offline tmd1  Ireland
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Default Best source of ones and zeros?

I haven't seen this here definitively before so I have to ask. I know it has probably been covered in bits and pieces many times over but I can't seem to get a consensus from the posts I have read.
I would like to know if there is one technically best solution for feeding a dac with information. As far as I understand it, the object of any transport is to get as much info from the CD to the dac as possible. The things that prevent this from happening are numerous. Among them are things at the laser like dirt, vibration, alignment and bad discs. Further down the line, there is jitter and probably emi.
So, out of this list of methods, is there any one that is the most likely to do the job best as I would like to select the best possible method and play around with it.
1. Dedicated CD transport, as in, off the shelf unit, fed to DAC via digital cable.
2. CD player with digital out, fed same as above.
3. CD/DVDrom drive in a computer, fed to DAC through SPDIF on back of drive.
4. CD/DVDrom drive in computer, fed to DAC through USB out.
5. Music ripped to harddrive on computer, fed to DAC through USB.
6. Music ripped to harddrive, fed to DAC through SPDIF out on soundcard.
7. Some other method, as i'm sure there are many.
I am assuming state of the art equipment for all of the above, to simplify the decision. In other words, the PC solution would be using a very quiet PC with a very good power supply and the best of equipment in general.
Thanks for your feedback, Neil.
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Old 20th September 2003, 08:55 PM   #2
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Hi Neil,

Build a PC based jukebox. Hard disks that can store of over 200 CDís are there. Take a quiet Fanless PC and put some 1 Gb Ram in it. Oh yes and a top gear audio card. Et voila bingo. The only thing you need is good and easy to use software that caches a complete CD from HD in Ram, no need to keep the HD spinning for long and during playback isnít it?

Cheers
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Old 21st September 2003, 09:15 AM   #3
tmd1 is offline tmd1  Ireland
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Thanks Pjotr. I am definately going to buy a quiet, fanless PC in the near future as a HTPC anyway. So, are you suggesting that the digital out will be from the sound card?
Again, is this technically the 'best' way to get the most information from the disc to the dac?
Neil.
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Old 21st September 2003, 11:08 AM   #4
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The main advantage of a PC based system is the ability reread the disk in the event of an error. But you can have that without the overhead of a PC but it is nowhere near as easy as building a PC. As to whether using a PC is the best way to extract data, that may well depend on a number of PC related variables.

ray.
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Old 21st September 2003, 04:53 PM   #5
OliverD is offline OliverD  Germany
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Hi tmd1,

actually you don't need to be concerned about data errors in digital audio. A very sophisticated error correction algorithm prevents read errors to show up at the digital output when reading from optical media. Only very badly scratched CDs will cause error correction to fail (which is clearly audible). Also PCs will reliably deliver the same 1s and 0s when you store music on them.

There is only one caveat: Some PC soundcards put the digital signal through a cheap low-resolution DSP to upsample to 48 kHz. But as you intend to use "state of the art" equipment, this shouldn't be an issue.

The problem that causes digital sources to sound different is more the "analog" quality of the digital S/PDIF signal transmitted. Remember, PCM data contains both amplitude and timing info of the analog signal it represents. While the amplitude data is quite immune to noise and distortion of the S/PDIF signal, the timing info is not. It suffers from being fed through lots of silicon and poorly designed interfaces (as the S/PDIF standard).

The good news is that you can eliminate this problem when you use an asynchronous sample rate converter or reclocking in your DAC. Technically this means your DAC runs from a very stable, local low-jitter clock instead of recovering the timing info from the input data stream. It is therefore much more independant from the quality of the source.

Are you using a DIY DAC? If so, look out for Elso Kwak's clock and his reclocking circuits.
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Old 26th September 2003, 09:42 PM   #6
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Modern PC CD-ROM drives and DAE (Digital Audio Extraction) software tools are far and away the ultimate way to get 1's and 0's off a CD. There are even lossless compression tools (like FLAC) that let you cut CD audio to 1/2 it's former size on your hard drive and play it back perfectly.

EDIT: In the last year or two the best drives especially burners from Plextor and the like can also report if they run into C2 errors and have to interpolate, so you will know for certain if the data is accurate or not, and whether you have to clean the disc.

The question of course is how to get the sound out of the computer and into a DAC There are a number of ways to handle it currently, most of them either A) Don't sound too good, or B) Are extremely complex and/or require further software tools beyond just a media player that may be hard to integrate into a system.

Use a good-quality soundcard, and one you are certain does not resample everything to 48,000. Ever since AC97(blech!) almost everything does resample, so you will have to look towards cards used in Pro-Audio. Consider some form of isolation, either transformers at the computer & DAC, or using TOSLINK optical cable, but if you do so you will CERTAINLY want a reclocking DAC. If you did though, I think the results would be pretty damn good.

EDIT: Even if your soundcard does not resample, look for ones that allow software to pass audio directly to the card, and not pass through the windows sound mixer and whatnot. If setup properly you can even rip a HDCD to your drive and play it back to a HDCD DAC and/or playback DTS/DD streams to a decoder.
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Old 27th September 2003, 01:56 AM   #7
jkeny is offline jkeny  Ireland
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Default Computer based Hi Fi

Neil,
I'm looking into this same idea and have more or less settled on using a silent PC as the centre for my HiFi (and ultimately Home Ent). With the use of EAC copying CD's to Hard disk makes sense and playback to outboard Dac with local reclocking (or asynchronous reclocking) seems to overcome any jitter issues.

The possibilities of also using PC for digital crossover and digital room correction makes this an almost overwhelming option.

I notice you are also in Dublin - have you found any cheap outlets for silent PC's?.

John
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Old 27th September 2003, 10:05 AM   #8
tmd1 is offline tmd1  Ireland
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Hi John,
I only recently started to look around for them. I usually find that www.elara.ie is the cheapest or close on most computer gear. They do sell the silent stuff too. the 10000 board seems to be the one to go for I guess.
Another though I had was the www.norhtec.com stuff. Shipping will be expensive from Thailand but the silent server for example is small and light so might not be too bad. He also makes audio gear and had this in mind with his computer gear I guess. He is a little flaky on delivery dates though or was when I last talked to him.
Let me know what you are thinking. I have some gain clones to build first but I would then like to concentrate on a source.
I also have an old laptop which might be a runner. I think it works but the screen is shattered. It has a cd drive and I guess a pcmcia sound card would work, or maybe there is a way of grabbing digital out inside the machine.
Good to know there are others here from Dublin. Makes it easier to find out the local stuff.
Regards, Neil.
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Old 27th September 2003, 11:56 AM   #9
jkeny is offline jkeny  Ireland
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Default PC based HiFi

Neil,
Thanks for the addresses - I will look into them.

I have built protype gainclones and they are fantastic for their price - I am thinking of rebuilding them and two more for use as amplifiers in active crossovers (using PC as digital crossover) on BBC Ls3/5a (although I may use speaker drivers in a dipole setup.

Anyway I had this thought to transfer my vinyl to PC - I can't afford a high end ttable & phono amp (I know that ultimately sound from high end TT will beat digital). So I thought

- transfer to PC from existing tt (ARiston Qdeck) through good quality soundcard without using phono amp

- apply boost and RIAA correction and possibly correction for shortcomings of TT to digital file stored on disk

- Now I have the CD equivalent of my vinyl


Has anybody done this or thoughts on it working?

John
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Old 27th September 2003, 12:42 PM   #10
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Method 5

Ive tried the digi out on the SB live SC using the CDrom drive as a transport and it sounded actually really good, as good as my TEAC VRDS T1. Then I ripped the data using WINdac to the PC and played from there, sounded much better then the CDrom drive spinning the silver. Then knowing full well that the SB upsamples to 48Khz and does about as good a job of that as a whale would do at running a marathon, I got a program called FooBar2000 or 2k if your gonna do a search. Anyway this upsamples real time using the processor to 48 removing the SB's need to screw up the data, this sounded again better, gains in clarity and spaciousness, massed voices were better separated, well everything was. Right then I got the KX drivers for the SB and loaded them on and tweaked the DSP connection settings to the simplest possible, two connections from the wav in to the digi out. This again brought about good improvements, mirco details sounded clearer. Anyway all of this is to remove the crap the SB does, using a USB (PCM2902 TI) is a simple as you can get takes the data from the PC and gives you a SPDIF out without any crap to mess it up. Im in the process of building a DAC around this and have good expectations of it. Knowing what clearing up what the SB can do to the sound, removing it entirely should bring about much better gains.

Matt
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