A freind and me are having a disagreement, he says that all DVD players will have the same sound quality if plugged up using a digital lead, its the amp doing the decoding and therefore determines the sound quality. He reckons that the only time the DVD player affacts sound quality is when you have it plugged up using 5 or 7 channel leads. This doesnt sound right to me as higher quality components and circutry would make a difference to the signal quality. Please help settle this disagreement!!

Cheers

Jon

[Garrett]

I would say he is wrong; it is like saying all CD players, etc should sound the same.

I have just upgraded a DVD player and the sound difference is astounding and that’s just on an old Pro-Logic processor.

[bobones]

This one has been done before. Firstly, it is not the same as cd players where audio is PCM (digitally encoded audio signal) and jitter plays a big factor. DD and DTS consist of compressed data that needs to be buffered and uncompressed (at the decoder) before it takes on any audio characteristics. This data is more like packets travelling over the internet than an actual audio signal. Unless the data is being highly corrupted or interfered with, I myself can't see how the sound quality can be substantially different from one dvd player to another. Even then, the differences wouldn't be subtle tonal ones, rather easily noticeble dropouts and glitches.

However, I'm optimistic that there will be a reasonable explanation of why DD or DTS can and do sound different from different players though

I have just upgraded a DVD player and the sound difference is astounding and that’s just on an old Pro-Logic processor.

Prologic decoders don't take audio from optical or digital inputs though, do they? You're hearing the differences in the players' analogue outputs.

[WeirdFish]

I dont know any technical reasons why but I can hear a difference in sound quality between my HK DVD25 & Tosh SD220. Both are feed optically to a Marantz SR5200.

[sapper]

This time last year, I had a home demo of the Arcam 88Plus DVD player.

Both myself and my wife detected an improvemtn in sound, more so than picture quality when compared to my Pio 717 DVD player.

It seemed more open, a better soundstage. The Parameters on my A1 Processor/amp had not been touched.

This weekend I am about to compare the Denon 2900 compared to my Pio 717, an dhopefully the Arcam 88Plus (or the 78)

Adrian

[Garrett]

OK bobones shoot down my above post, but what about the differences in the type of digital cable used, as the signal is digital, in theory there should be no difference in the end signal through it, yet people can tell the difference.

[John Dawson]

Bobones - with respect, you have fallen into a common trap when discussing the transmission of compressed data across SPDIF. Although the data has to be buffered at the receiving end, the clock used to clock out the data has to be generated from or at least synchronised to the SPDIF stream. If that stream has a lot of jitter on it then some of that will be passed through when generating the master clock in the downstream receiver.

There are ways round this, especially in expensive AV processors (crystal controlled PLLs etc), but the clock regeneration circuits in mainstream receivers leave something to be desired, so if they get a very good quality stream (as for example from any Arcam DVD player!) then you may well hear the effect of this when the signal has been decoded back to analogue.

Sincerely,

John Dawson (Arcam)

[bobones]

Fair enough John. I knew there would be a reasonable explanation.

[bonzobanana]

There does seem to be some confusion on this issue and must admit I'm confused myself. Dolby's own site who you would have thought were the top experts on it recommend optical connections, where as many magazines etc recommend coaxial as better sound. Certainly if theres any stage that should effect sound it should be the actual transmission to amp via cable.

I used to be a salesman at a hifi store and I'm a bit ashamed to admit it but at times we used to demonstrate the same cd player etc twice in a row as a joke because the hardware was stacked in a corner and we would simply swop phono connections at the back and the customer would be hearing the exact same sound again. That wouldn't stop some customers going on about one having better bass than the other or sounding smoother or instruments sounding more clear. It was difficult to keep a straight face at times and fake coughing sessions were common.

So I've become a bit of a cynic. What we really need to do is blind tests where people have to prove that they can tell a difference between output quality. This can be done by connecting various players of different price ranges and see if people can lock on to which is which without seeing which player is connected to the amp.

Thanks everyone for your reply!

Originally posted by bobones
Fair enough John. I knew there would be a reasonable explanation.

I can't believe you caved.