Lettori CD Hi-end e Wireless Hi-Fi

Qui di seguito un interessante articolo (purtroppo solo in inglese), di un tizio che dopo aver speso 1.500 sterline per un lettore cd hi-end (assemblato in Italia, questo:http://www.unisonresearch.com/unico/prodotto.aspx?idp= scopre che dentro c'e' un lettore cd rom della ASUS come trasporto. Ma poiche' funziona bene, lo sfrutta anche per altri scopi e ne approfitta per usare il dac del lettore come input per la sua musica digitale wireless.

http://www.trustedreviews.com/multimedia/review/2006/06/01/A-Lossless-Ordinary/p1

Music playback is undergoing a massive revolution at the moment. Not since the advent of digital when Compact Disc replaced vinyl has the music industry been in such turmoil, and the effect that illegal download websites and the device that brought it all to the masses – Apple’s iPod – have had is well documented. But it’s not just portable and PC-based music feeling the heat of change.



The iPod made digital music compression mainstream.


Music in the home is, slowly but surely, undergoing a transformation too. Media Center PCs and, more recently, wireless multi-room audio systems are beginning to creep into the mainstream, and people are replacing their old hi-fi systems with more modern, easier to use solutions.

Traditionalists will pooh-pooh such setups as not serious, never-capable of rivaling proper hi-fi 'seperates' for sound quality or musicality. After all, when you spend a couple of grand on a dedicated CD player, it’s bound to sound better than a load of music files streamed off your PC, isn’t it?

For years I’ve agreed with the audio snobs. I sneered at those listening to their music on PC-based audio systems. I thought that a do-it-all appliance such as a PC would never rival dedicated, carefully-designed and, most important, expensive hi-fi equipment. But a couple of reviews I’ve had the opportunity to write recently have got me thinking.

Compressed digital music files can never sound as good as a high-end CD player right?



The question I wanted answered was: is it possible to enjoy the best of both worlds, combining the convenience of music libraries with the high-end sound that audiophiles value so much? In theory, I thought, it was. So I set about finding out if it really was practical.

The two devices that set me off on this quest were Sonos’ ZP80 player and Slim Devices’ Squeezebox 3. Both are wireless music systems and both are equipped, alongside the usual analogue outputs, with digital outputs. That might not sound significant on the face of it, but the digital outputs mean that you can cut the PC-related hardware almost completely out of the picture, leaving the music reproduction to proper hi-fi equipment at the end of the signal chain.



In theory, you can stream the digital signal, via S/PDIF, all the way from those files on your PC directly to a high-end DAC (digital to analogue converter) or home theatre receiver, without having to involve the PC in the decoding process at all. And if you combine this with lossless music file compression systems, such as FLAC (Free Lossless Audio Codec), WMA Lossless and Apple Lossless, which allow you to store bit-for-bit identical copies of your music on your computer in less space than standard CDA files, the result should be just the same as plugging a CD transport into that DAC or home theatre system.


Even storage isn't too much of a problem. Though compressed lossless albums still take up 200MB to 300MB per album, with mass storage so cheap these days you can encode and store even a large CD collection for not much cash. You can buy a 300GB hard drive, for instance, for around £75 inc VAT now, and one of these will store a whopping 1,228 albums at 250MB in size.

Of course those in the know will waffle on about jitter and how S/PDIF, which embeds the clock signal in the same stream as the audio information, isn’t the best means for getting the cleanest digital signal into your DAC circuitry. That may well be the case, but if you’re still sceptical, take note of the following salutary tale…

I have, for my sins, a reasonably expensive hi-fi setup at home. The star of the show is a hand-built, Italian designed CD player – a Unison Research Unico CD. It cost me £1,200, plus £180 for a cable upgrade, sounds wonderful and the hi-fi press agrees.

http://www.unisonresearch.com/unico/prodotto.aspx?idp=8

Anyway, out of curiosity I opened it up one day and made a surprising discovery. Behind that expensive, sand-blasted aluminium fascia sat a CD-ROM drive. Yep the sort of drive you might find in any modern PC (albeit slightly modified) was acting as the transport in my boutique music system.



With the lid off my expensive [b]valve-drive Unison Research Unico CD player I was shocked to find that the source of the digital signal came from the S/PDIF TTL output on a modified ASUS CD-ROM drive.
The business end of the player – the valve-powered DAC electronics – simply takes the S/PDIF signal straight from that drive via a two pin TTL connection, before turning it into analogue audio.

In theory, then, supplying an equivalent TTL signal to the CD player’s DAC circuitry, direct from the Sonos and Squeezebox wireless music players, would allow me to compare the CD and wireless players' performance back to back.

So I did exactly that, bought a coaxial to TTL digital signal converter (coaxial has lower voltage than TTL) and plumbed each of the wireless systems directly into the DAC half of the CD player.Next I encoded around fifteen CDs into the open source lossless FLAC compression format and settled down to a good long listening test.



First up was a back-to-back comparison of the Sonos and Slim Devices systems using their coaxial S/PDIF outputs. Neither the choral strains of Mozart’s Requiem, the intense bass punch and electronic sounds of The Prodigy’s Girls nor Diana Krall’s soft jazz standards revealed any kind of disparity between the two. I couldn’t hear any difference.




Here you can see the digital input from the wireless device, converted from coaxial to TTL, connected directly to the DAC circuitry on the Unico CD.

Next, I used my £250 Denon DVD-2910 and the Squeezebox, again output via coaxial digital output, to compare CD with FLAC over wireless. And this time there was a small difference. Instruments seemed to stand out a little more with the CD, boosting the sound staging with the breathy vocals of Diana Krall standing out in particular, but importantly, I was hard pushed to say whether this was as a result of a slightly higher output from the DVD player, or whether the sound was a quantifiable improvement. Fiddling with the volume levels between players seemed to iron the differences out.



Finally, came the big test – comparing back to back with the CD player in its original state, and here the difference was more noticeable. Both with the Sonos ZP80 and Squeezebox as source components, the sound wasn’t quite as dynamic as it was with the CD player. The piano of Ben Folds cut the air with the high end player in a way that the same sound from the FLAC file over wireless just didn’t. Andreas Scholl’s piercing vocals filled the room better and sounded richer in a way that couldn’t be solely attributed to a difference in digital signal input levels.

Now this could be due to any number of reasons, from difference in output levels, to the much shorter signal path or the fact that the two components have been extremely carefully matched and tweaked in the lab (rather than my front room) to achieve the desired sound quality. But the gap in sound quality is there, and it is noticeable.

There’s a clear answer to the question of whether wireless music systems can replace a dedicated CD transport in a high end audio system and that is almost, but not quite.



Yes, you can do it, and it will sound great, especially considering how far the signal has to travel before it hits the DAC circuitry. In fact in terms of value for money this kind of setup has the potential to sound utterly jaw-dropping when the right components are chosen and for anyone looking to go into wireless music in any kind of serious way, I’d say it’s well worth investing in a decent DAC. The DACs in these players, though good, can’t match the sound you get from a dedicated box.

Despite this, for whatever reason, the integrated CD player approach still holds the edge. Whether it's enough edge to persuade me that my next hi-fi upgrade is an even more expensive CD player, however, is another matter. I think I'll just bide my time and keep experimenting in the hope that wireless audio nirvana is out there, somewhere…

Oltre alle considerazioni di cui sopra, ne aggiungo una personale. I lettori CD o DVD rom possono essere un ottima sorgente digitale da collegare a un DAC. Ne avevo gia' parlato un paio di mesi fa qui:

http://t-class.niceboard.org/sorgenti-cd-dvd-giradischi-pc-ipod-ecc-f12/lettore-cd-rom-come-cd-player-t1482.htm

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