Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems HTPC vs. the need for DVD (or HD-DVD / Blu-Ray)

Mark_H - no, the servers don't guarantee a perfect rip. But that's ok, because you don't have to rip on the server. With my Imerge, I rip in EAC, then upload the wavs to the Imerge over Ethernet.

Regards

Mark

Mark,

Thanks - that is very good news.

Mark

The interface between PC/server/Mac and the sound system seems to be a degrading factor. Personally, I found that CDs played by the DVD-Audio drive in my G91 sounds far better than uncompressed WAV files my Mac mini with a USB external sound card. The sound is put directly from the G91 via SPDIF to DSPs (7000). G91 wins big time. Both sources go throug upsampling etc that the G91 does. Theoretically there should be no difference. And a certainly WISH (my G91 is only a loan) that a music server could be sufficient - both for practical and financial reasons (a Mac mini costs $600, a G91 $6000 or more!). But to my ears at least, the difference is very real. The Mac sound is harsh, less detailed and has less "impact".

You need to decouple the PC from the audio system to avoid PC power supply induced nastiness and conductive noise through the interconnects. This is where the wireless Squeezebox (and other wireless servers) comes in as they are physically decoupled and so transmits no noise.

Cheers,

Mark

That might be true if the transmissions are analogue. I don't believe noise does anyting to digital transmissions. They are either "on" or "off", they lock or they don't lock. I would tend to think the explanation lies in the "translation" from one interface to another, i.e. USB/SPDIF. These are subtle differences, it is absolutely not a question of "bad sound" from the Mac. I tried Airport express - same phenomena (not the same characteristics, but still a difference). Still OK sound, but not as good as G91.( In addtion, wireless transmission tends to be somewhat unstable - especially if you transmit uncompressed files. Didn' work very well in my house.)
A difference from G91 is also evident when I use another CD/DVD player. SPDIF out- same data from Red Book CDs, and everything is wired through G91. Flatter, more uninspired sound than from the G91 drive. I have absolutely no explanation for this. Neither do a friend of mine who is an electronics engineer (and hifi buff). He hears the same as me...

I don't believe noise does anyting to digital transmissions. They are either "on" or "off", they lock or they don't lock.

You'd think so.

Digital streams, and in particular, PCM, are very susceptible to jitter. Any noise, whether from the device's power supply, RFI, EMI, or another device connected by a conductive interconnect can cause jitter. And jitter degrades digital sound quality...

http://www.tnt-audio.com/clinica/jitter1_e.html

Typically, anything that can be done to improve jitter performance brings sonic benefits. Meridian's on MHR protocol, for instance, claims to do this...

As you say yourself, digital *should* be perfect - so you need to ask yourself why something much simpler than your CD player (with all it's moving parts and potential for errors), eg a hard-drive rip being served digitally sounds worse than your CD player.

If jitter isn't the culprit then there is either something wrong with your rips (eg they contain errors) or with the Airport Express (perhaps it's jitter-prone).

My experience with wireless is that it either works and is stable or it doesn't. Some juggling may be required to get a stable signal, but once achieved it should be fine. Many people are serving WAV/FLAC over 802.11g without issue.

Cheers,

Mark

Jitter shouldn't be an issue here, as G91 re-clocks. And as far as I know, jitter at the source can be eliminated later in the digital chain. Or am I misinformed?

My Wi-Fi system is set up as 802.11b/g (several old receiver cards in the chain) - so that might explain the instability.

Some reclocking solutions are more effective than others. If the G91 reclocks perfectly then there would be no difference between the CD player and the Airport Express, assuming jitter is the only problem.

The point is, a perfect lossless rip of a CD, served digitally over an error-free cable *should* sound better than any CD transport available. If it doesn't, it's not the fault of the concept, but rather the implementation.

Cheers,

Mark

Mark,

You are seriously confused about the transmission of digital data. This idea that you have of “decouple the PC from the audio system to avoid PC power supply induced nastiness and conductive noise through the interconnects” is complete garbage. Also “physically decoupled and so transmits no noise” is complete garbage.

I am sorry to come across as combative.

This hokus pokus is common in analogue audio and wine tasting. But just does not have any place in digital audio. You simply have no idea what you are talking about. You are simply making this stuff up!

It is not that complicated, if all of the bits are getting from the source to the destination then all the bits are transmitted perfectly. There is no room for argument, done, zilch, end of discussion. There is no room for the hokus pokus anymore. That is why we pay up for a digital audio system, so we can listen and not be bothered by hokus pokus.

Mark is correct to a degree. Some PC's create a lot of EM noise and the switching supply can create a lot of noise although not all of them are horrible. Still digital audio connections from PC's will sound better via optical connections most of the time or via a connection that eliminates the copper conductor connection that can cause ground loops. It varies from system to system. The closer your system is to the very highest end in sound quality the more these type of connections will rear there ugly head. Remember the noise conduct into the circuits that are dejittering and cause jitter. I find that the PLL system in the 518 does the best job at minimizing not eliminate this type of problem. FIFO just doesn't cut it when the jitter is bad. FIFO is good for that last ounce of detail but needs a clean stream to begin with. Something I discovered once with a 8 meter toslink cable that had a lot of jitter. A direct connection to a 568 and it was brittle and compressed sounding. Even Dolby Digital sounded like crap and DD is more robust from jitter problems. Feed the same cable through a 518 into a 568 and it was night and day better. Use a short optical cable for the best results from a PC if you go that route. I've run into these problems so I don't even consider them anymore. I agree with Mark.

Ron

"It is not that complicated, if all of the bits are getting from the source to the destination then all the bits are transmitted perfectly."

Isn't the debate here, whether or not all the bit are transmitted perfectly and with perfect timing?

Cliff

I am sorry to come across as combative.

Not combative, just uninformed :p

Mark