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The Pink Fish CD Player

M

Markus S

41 - 29
Here’s an idea which owes a lot to work done by Audio Physic in Germany:

Take one CD-Rom drive (or DVD player, if you have one lying around); read content of CD onto hard disc drive. Read CD data into RAM chip; decode content of RAM chip via PC sound card.

Apparently, one of the larger problems with CD as currently implemented is that data have to be read and decoded „on the fly“, i.e., while the disc is spinning. Audio Physic say that reading the data from a solid state memory greatly reduces all manner of errors, including jitter.

I would love to have a CD player like that. The basic bits should not be that hard to assemble. However, we’d need a suitable display for the dedicated computer, and, more importantly, some software for implementing all of this.

Software-wise, I am an absolute ignoramus. Is there a forum member who’d volunteer to write this? Linux should be a suitable basis.

Markus
 
Software for this is already available, just look for a CD ripping package. This can then be partnered with a few shell scripts to automate the ripping of each track, copying it to a Ram disk and streaming through a sound card.

The problems I see with this system are firstly, that it is expensive to do this properly in a semi-dedicated form - a really good soundcard and the necessary soundproofing for the PC will set you back a couple of hundred, also a PC is a fairly noisy environment and this is likely to compromise the maximum level of sound quality you will get. Unfortunately, as soon as you move the DAC off board, you reindroduce the jitter problems you are trying to avoid.

I think some of the big american CD players use this idea by having a decent amount of RAM on board which the DAC accesses locally, providing a buffer.

I saw this thread and thought it might be a plan to design a traditional CD player, now that would be fun :)

See http://www.steinmusic.de/indexeng.htm for ideas...

Cheers,

Ed
 
I think most of the problems Ed mentions were addressed by Linn when they developed the Knekt system with the Tunbox etc. If I'm not mistaken they couldn't get the sound quality anywhere near that of the Ikemi.
 
quite a few cd players and dacs do this already. various meridiens, levinsons and the chord dac 64 all have substantial ram buffers in them and the meridien uses a cd rom drive and will re-read data if there are errors. wouldn;t call the sound flat earth though.
cheers


julian
 
Prowla

Check out the Lynx 2 or the Lynx 22 soundcard. The specs are amazing. I've never heard one thougjh.

The RME Digi 96 range are more reasonably priced. I use one of these for my vinyl to CD transfers and the results sound very impressive played back on my CDX & XPS in a Naim 82 250 system

Eddie
 
According to what I have learned from AudioPhysic, there is a sonic benefit from spooling some of the digital data into a RAM buffer and clocking it out independently, but an additional benefit occurs when one entire song (or CD) is spooled into a _big_ RAM buffer, and the CD drive is powered down completely. The conclusion is that the operation of the CD drive mechanism is pumping copious amounts of conducted and radiated noise into the rest of the drive electronics. A moderately-sized RAM buffer goes some way towards improving the sonic situation, but inasmuch as it doesn't allow the drive mechanism to be turned off completely, it doesn't go far enough.

I have a Marantz DR-17, which is a stand-alone CD player/recorder. The sound is at its best when the DR-17 is used as a DAC only. Engaging the recording standby causes a perceptible degradation in sound quality, and spinning up the CD drive makes matters considerably worse. This experience would seem to confirm AudioPhysic's suggestion that enough RAM is employed to enable the CD drive mechanism to be turned completely off.

Regarding PC-based extraction programs like EAC, I was told by a programmer that converting a song from a CD into the WAV format itself would introduce some alterations in the data. However, I am not a programmer, and have no way of verifying if this is true or not.

hth, jonathan carr
 
Originally posted by jcarr
Regarding PC-based extraction programs like EAC, I was told by a programmer that converting a song from a CD into the WAV format itself would introduce some alterations in the data. However, I am not a programmer, and have no way of verifying if this is true or not.
Click to expand...

Jonathan,

that depends on the hardware as well as on the software; e.g. some drives are more jittering-prone than others. This is why EAC
and CDParanoia
exist. They try to reduce the Jitter with the means of some dedicated algorithms.

It is always possible to run some CRC checks on the source and the ripped data; if the resulting checksums are the same, the data was not altered.

What strikes me more on this matter is the rather quick spreading of copy-protected CDs, at least in Germany. Some of them are protected in a way that they are not playable on computer drives (I have even seen reproducable crashes of several notebooks when such a disk was inserted).

How do the Meridians cope with these?

Best regards,

Oliver
 
Another problem with reading a CD to RAM before playing is that it would take around 1 minute (with a x52 CDROM drive) between hitting play and you hearing any music :(

If I were designing such a player:

I'd use a sound card with a digital output in the PC and then build a separate DAC (shock horror) with the required RAM in the box with the DAC. The link between the PC is then purely digital and only needs to be bit acurate i.e timming and PC noise polution is largely irrelevant. Jitter would be no more of a problem than with a single box player since for play back we are only using the RAM and DAC which are run from the same clock in the same box.

I wonder if we could get into arguments about which sort of RAM sounds best: SD, DDR, EDO SRAM etc... :)
 
A couple of things:

Eddie:
I'm not sure the Lynx things could quite compete with a CDX... (However, if/when I decide to get a new PC soundcard, I may just remember the name :).)

coredump:
What has jitter got to do with digital extraction? I do not believe that there are digital errors on CD data extraction (of an undamaged disk, of course). If there were, then CDs would be useless for storing data, making backups, distributing software, etc. Copying the audio files from the CD is a straightforward binary file copy, not to be confused with ripping to MP3.

imarks:
I know this is not quite what jcarr suggested, but perhaps half-way: you don't have to read it all to RAM before starting playback, just read ahead into a cache. Since CD-ROM drives read at 50x or more, they're well capable of loading plenty of data within the pause before the start of track 1. (Also, if you had loads of ram and an autoloader, then it could perhaps read in the disk when you put it in, rather than waiting for you to press "play".)
I also think that Naim don't like separate DACs because it's difficult to sync the clock between the source drive and the external DAC (so leading to jitter).

aside:
I remember going to a Heathrow Hi-Fi show a few years back and seeing a CD player that was based around a computer IDE CD-ROM drive (in a rather nice wood box, with the vendors own electronics). I can't remember the name though.
 
I have a CDX / XPS and a NEC Spinwrite (a stand alone SCSI reader that has a digital out, and can be used without the PC attcahed) fed into a Flying Cow DAC. The Flying cow is around $250 and the NEC $10 on EBay.

On direct A/B there is almost no difference between the two, and that's with the Flying Cow running off a 'wall wart'.

The price delta hardly justifies the convenience of a remote!---- go figure!

Regards

Martin
 
Prowla, I think the CD player you are referring to was built by Redgum - Australian outfit. Got good reviews at the time. Several current cd players now use IDE CDROM drives - Resolution Opus 21, Ayre etc - and they all make a 'virtue' of using such a commodity in otherwise very expensive devices!

Overall I'm not sure the big-RAM-disc approach gains anything worthwhile. The essential problem still comes down to clocking the bits out of RAM and through the DAC - after all the only place where jitter really matters is at conversion. If you can do this properly, then why not just do it using the FIFO buffer in every CD decoder (eg the Philips SAA**** series) and not bother with the complication.

Besides which, powering huge gobs of RAM, with its typical 2khz refresh, inside the cd-replay device then gives you potential problems with lots of PSU noise smack in the middle of the ears' sensitivity peak; afterall PC ram is hardly characterised for low noise and other hifi-nutter concerns and it does radiate huge amounts of EM noise. Those offboard DACs which use large ram buffers do it just to ameliorate the inherent problems of transporting and converting the bits away from the clock that dragged them off the disc. Bah and humbug....Occam's razor and all that. If the CD drive mech causes noise and degradation, fix it...it's a smaller problem than the proposed solutions, and would come down to some half-decent shielding and PSU regulation. For a start it doesn't help that most CD drives moters are driven directly off the H-bridge outputs of the CD decoder chip - because thats what it tells would-be cd-player-engineers to do in the decoder datasheet , no doubt* A couple of buffer opamps, a lowpass filter and a separate psu deals with that nicely...

MC

*It is shocking how many CD players' digital and analogue stages are only literal implementations of the 'suggested' circuits in component datasheets - where the suggestions are only a 'get-you-started ' shorthand for potential applications. But of course engineering costs money...
 
If the CD drive mech causes noise and degradation, fix it...it's a smaller problem than the proposed solutions, and would come down to some half-decent shielding and PSU regulation.
Click to expand...

The ubiquitous Marantz CD63 that I have some experience with is a classic example of this. The KI Sig just adds a toroidal TX, a beefier chassis and a bit of component fiddling, with bugger all engineering content to the really critical bits.

As a consequence the single 5V rail, which powers all the delicate digital stuff, including the critical DAC / Clock has a massive amount of noise, that rises dramatically when one hits 'play' :rolleyes:

If ever there was a reason for using seprate PSU's, this is it :)

Andy.
 
Originally posted by prowla
What has jitter got to do with digital extraction? I do not believe that there are digital errors on CD data extraction (of an undamaged disk, of course). If there were, then CDs would be useless for storing data, making backups, distributing software, etc. Copying the audio files from the CD is a straightforward binary file copy, not to be confused with ripping to MP3.
Click to expand...

Prowla,

jitter has got a lot to do with digital extraction of CDDA. You are mixing up proper file systems (i.e. ISO9660, HFS) and CDDA. CDDA is not a proper file system, but just a stream of time-based digital information. This is why audio CDs are not 'mountable' like ISO-formatted disks (with the exception of the Unix WM "KDE" which is able to deliver a 'preview' on audio tracks).

Using a proper file system like ISO, you can rely on the file system's techniques to ensure file integrity (CRC checks, etc). CDDA does not have these.

Generally you can say that some drives jitter less (notably Plextor), others more (LG). The links in my original posting will give you an overview.
 
Originally posted by prowla
What has jitter got to do with digital extraction? I do not believe that there are digital errors on CD data extraction (of an undamaged disk, of course). If there were, then CDs would be useless for storing data, making backups, distributing software, etc. Copying the audio files from the CD is a straightforward binary file copy, not to be confused with ripping to MP3.
Click to expand...


Prowla,

jitter has everything to do with audio extraction from CDs, because many systems are very poor in this respect.

What you have to realise is that this PC jargon has an utterly different meaning to that in hifi. In PC DAE it means where an audible error is caused by the inability of the CD-ROM drive to extract all the right bits in the correct order. You have to realise that there is no sequential numbering of the sectors on the disc, because noone ever conceived of reading the data off disc and into a PC. If the CD-ROM comes across the sort of error which would be corrected or interpolated by an audio player (CD-ROMs do not do this), or has to pause momentarily whilst the PC catches up then it has to guess where to re-start because there is no way for it to do this properly.

If you see 'jitter' on a WAV file in a PC audio editing program you will see full-level square waves and other nasties which will make you wonder how your tweeters survive playing the resulting copied disc.

cheers, Martin
 
Originally posted by coredump
Generally you can say that some drives jitter less (notably Plextor)
Click to expand...


CD,

I didn't find my SCSI Plextor CD-R drive any better in this than a run-of-the-mill CD-ROM.

I now have a Yamaha CRW-F1 (sadly now discontinued) which is almost flawless at DAE, certainly the best I've ever seen.

cheers, Martin
 
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