Digital Outputs - DVD (1 Viewer)

[Roy Wallace]

Hello all: I have aquired my first DVD player and would like some input regarding the digital outputs it has. Until I can upgrade, I will be connecting my Sony DVP-S360 to a ten year old Sony STR-D2020 receiver. This old unit has both optical and coaxial digital inputs. Which is better- if there is a difference?
Also, I would like your input regarding my surround speakers. Currently I have a pair of Realistic Minimus 7's mounted about 8 feet behind my sitting location,and 7 feet off the floor, and a few feet wider than my front speakers,(An old pair of JBL Decade 10's, but that's another story)angled slightly inward.
This arrangement suits me fine for my limited system, but I am anticipating an upgrade for AC-3. My concern is their mounting position. Is this high and wide position desirable for the newer systems, or should I be anticipating some drywall work to move the surround location?
Thank you for your guidance.

 

[DaViD Boulet]

Happy to be the first to post to your controversial topic
Much debate exists about this issue in the audiophile community.
Firstly, feel free to experiement and let your ears tell you what to do.
Aside from that, here's my opinion/experience:
If one has the choice, the coaxial connection can sound better provided that a good true-75 ohm cable is used. "high end" video composite cables are often 75 ohm. But so is RG-6. so get yourself some shielded RG-6 with a nice solid copper core, get some F-> RCA adaptors for $1.00 each at rat shack (you can get all this stuff there) and for less that $20 you can have your state-of-the-art coaxial digital cable. I did this and it sounds as good as the Audio Alchemy "powered" digital cable I'd been using (which sounded better than most anything else I had tried).
Use as short a run as possible and try to minimize bending the cable as this affects impedence and consequency reflections in the signal.
How can any of this affect a "digital" signal? It doesn't...but is does affect the *analog* time-clock signal that's sent along the same cable as your digital bits. Most dacs are designed to "lock on" to this incoming analog clock signal and use it faithfully to convert those 1s and 0s back to music.
A bad clock signal means the bits get converted at the wrong time...which means bad sound.
You may have heard this called "jitter".
IMO most of the "digital" sound audiophiles complain about has to do with Jitter. It's amazing to me how much difference it can really make. I have 3 transports (2 LD players and 1 DVD player) and I can hear differences between them...even when I make digital dubs to minidisc!
How scary is that?
-dave

 

[cody meche]

david any reason for the solid core coax, reason i ask is that i have used solid core for other applications and in the long run have had signal degredation due to aging of the wire and breaks in the solid core. i realize that its placement of the cable restricts it from movement and bending and all around not being touched, but i was just curious.

as far as the initial qstion at hand i myself use the tos link or fiber optic patch just because in my lineof work i deal with alot of fiber connection confgurations and i know what with i deal with in this matter and feel confortable with its capability to perform the way it was designed.

thanks

 

[SteveDinn]

Am I the only one here who doesn't think this matters one iota? The signals on these cables are DIGITAL. You get a perfect signal, or you get no signal, there aren't any in-betweens. As long as the cable used can handle the bandwidth of the bitstream, then it is fine. In my opinion, people who buy expensive digital audio cables are kidding themselves.

On the other hand, there is the argument that when using optical cables, there are two extra conversion steps in getting the signal from your DVD player to your receiver. Internally to your DVD player and your receiver, this digital signal exists as electrical pulses, and it can be transmitted in exactly this manner on a coaxial cable. Data transmitted via optical cables must be converted into light pulses first. Some argue that the process of converting the electrical signal to light, and back again at the other end is potentially lossy. Coaxial cable, though, is more susceptible to signal degredation over long runs than is optical cable, but since we're probably only talking a 3 foot length here, it really doesn't matter.

So, if I were going to suggest one or the other, I'd say go with coaxial, but don't spend a boatload of money on a cable.

 

[DaViD Boulet]

The signals on these cables are DIGITAL. You get a perfect signal, or you get no signal, there aren't any in-betweens.

Steve, the fact of the matter is that the digital architecture in place for consumer equipment places *both* digital *and* analog signals in the same carrier wire when transferring digital data.

What's analog about a digital signal? Well...you're right that the discrete amplitude information is truely digital...just bit words. But the *time clock* that is sent with that data to the DAC or decoder is 100% analog. And as any analog signal is subject to degredation.

Even if you have 100% perfect bit-recovery at the receiving end (which you very well may have) if the *analog* (I'm saying that over and over again because so many people don't believe it. It's fact!) time-clock gets messed up in some way...like becomes irregular or erratic...then you get "jitter" when the DAC tries to slave to this clock for d/a conversion.

Anamolies in the analog time-clock signal can even affect the decoded sound of compressed audio bitstreams like DD and DTS!

So there you go. That's why people can hear the differences between cables (sometimes) and transports (more often). It's not a digital issue at all. It's an analog one.

Remember...the sound you get from digital audio is really only 50% digital...the vertical resolution is pure digital. But the horiztonal resolution of the waveform is governed by the timing between those bits as they are converted back to analog.

-dave

 

[SteveDinn]

Ahhh..I see. It is clear to me now that I should have read your first post in this thread a little more closely
Thanks for clarifying that for me.
I guess the real solution to all our woes won't come until there's just one (and only one) digital cable running from our DVD players that contains everything, video and audio, in a time-synched manner.

 

[DaViD Boulet]

The real solution is to somehow completely decorrelate the time-clock that governs d/a conversion in the DACs from the incoming clock signal sent with the digital bitstream.

If the Dac could just say "aha...the incoming clock is an averaging 48 kHz...so I'll just create my *own* clock ticking away at 48 kHz to convert this audio back to analog" we'd solve jitter in one fell swoop.

That's what the digital Gensis Lens did...but it wasn't a DAC...it was a jitter filter that stood between the transport and the dac. It works like a charm to clean up bad transport sound (due to jitter) -- it recreated it the clock from scratch for the outgoing data) but you still gotta pipe that wonderful reclocked data though another cable to the d/a converter/decoder.