optical out ?

[radish]

Coincidentially, one of the arguments that says a hard drive is better than a CD is that the conversion from magnetic to electrical is far simpler than optical to electrical...

*Snorts milk out of nose* HA! That's great. Guess whoever came up with that thinks a lightbulb is really complex.

[seanadams]

Further to this... physics gurus feel free to correct me: the flow of photos can change instantaneously, whereas electrical signals have to fight the inductance/capacitance of the cable.

This means that any timing noise on an optical link comes only from the transceiving modules, which according to my own tests meet or exceed the performance of electrical links of 1m+.

[LavaJoe]

The reason I've heard from some engineers is that the conversion process from one medium to another (eg. optical to electrical) is where there is the greatest probability of adding jitter. With coax, everything stays electrical, but with toslink, the signal must be converted from electrical to optical and back.

Coincidentially, one of the arguments that says a hard drive is better than a CD is that the conversion from magnetic to electrical is far simpler than optical to electrical...

Yeah, that just silliness. There are so many complex processes going on from the magnetic platter to the output signal that it hardly matters if an an optical conversion is introduced somewhere in the chain (even if that *did* qualify as "more complex")!

Sounds like classic audio salestalk to me!

[LavaJoe]

On Mon, 2005-12-05 at 16:10 -0800, LavaJoe wrote:
> seanadams Wrote:
> > Personally I lean towards optical - if you think timing and signal
> > integrity are important in hi-fi, imagine high-capacity
> > inter-continental telecom - there's a reason it's all fiber.

> Back in the Early 90s,
>[snip]
> The sales guy was very convinced that coax was far superior to toslink.

It was probably true back then, especially at consumer prices.
In the late 90s, home theater drove a lot of improvements
in the whole toslink space. I'd be surprized if there
is still the "far superior" difference. But YMMV and all that.
Plus coax lets you spend $200 for a "digital cable"
ahahahaha.

--
Pat
http://www.pfarrell.com/music/slimse...msoftware.html

When I bought my current speakers in 1984 (Advent Legacy models), an emblem on the box said, "Digital Ready." That made me laugh even back then! Gosh, good to have speakers that can handle a CD player...!

BTW, I just refoamed the woofers in these speakers (they were suffering from the dry rot of the surround foam that happens to all speakers, I just learned), and they sound fine again. Yeah, I could do better, but it's good to make these old guys last a bit longer!

[PhilNYC]

*Snorts milk out of nose* HA! That's great. Guess whoever came up with that thinks a lightbulb is really complex.

Actually, in this case it is, right? The light has to turn on and off at nearly 44,100 times every second at a rate that allows for a sensor to accurately read and understand. How do you make that light bulb go from off to full intensity and then back down to completely off? Also remember that the bulb is being turned on/off by an electrical signal. To do this without adding jitter is certainly very complex...

[PhilNYC]

Sounds like classic audio salestalk to me!

Interesting, tho, that it was engineers (more than one) who gave me this explanation... :-p

[Andrew B.]

One reason that optical is superior to coaxial is that it eliminates the possibility of ground loops between equipment. This can make a big difference to the sound quality as well as removing annoying hum.

I experienced this first hand recently when I tried a borrowed TAG DVD transport in place of my usual cheapo one into a variety of DACs, including a Chord DAC64 and a Benchmark DAC1. The Benchmark is essentially immune to incoming jitter and is as transport agnostic as any DAC I've ever heard (in fact I think it is completely irrelevant which transport you use it with) and the Chord DAC is pretty good in this respect too. But there was a clear problem with the sound just "collapsing" when the TAG DVD was used with a coaxial lead instead of an optical.

Also when you are trying to get sound out of a computer soundcard you will often experience ground loop issues if using coaxial.

Andrew

[LavaJoe]

Actually, in this case it is, right? The light has to turn on and off at nearly 44,100 times every second at a rate that allows for a sensor to accurately read and understand. How do you make that light bulb go from off to full intensity and then back down to completely off? Also remember that the bulb is being turned on/off by an electrical signal. To do this without adding jitter is certainly very complex...

It would be impossible with a light bulb (the persistence/glow would be too long). With optical fiber, the emitter is an LED or laser diode, and these can be switched very fast.

[LavaJoe]

Interesting, tho, that it was engineers (more than one) who gave me this explanation... :-p

I was an electrical engineer in college (you can't spell "geek" without EE!), and I don't know any basis for thinking that optical coupling is necessarily more "complex" than electrical. With electrical, you have to worry about factors like impedance, etc. And ground loops, as someone else said.

I'm no expert in optical emitting technology in terms of pulse edge timing, etc., but I would think it could be done in a high-precision fashion for a digital signal if care is taken.

[LavaJoe]

Further to this... physics gurus feel free to correct me: the flow of photos can change instantaneously, whereas electrical signals have to fight the inductance/capacitance of the cable.

This means that any timing noise on an optical link comes only from the transceiving modules, which according to my own tests meet or exceed the performance of electrical links of 1m+.

Sean, it's a matter of bandwidth in either case. An electrical signal can only change as fast as the fastest frequency that can travel down the cable (and this does depend on inductance/capacitance, etc. - but it's been a long time since I studied this stuff!).

For an optical cable, the fastest the signal can change is the highest frequency of light that can travel down the fiber, and yeah, light in the infrared/visible range is *very* high frequency (4 x 10^14 Hz for red, for example, whereas coax cables are more in the MHz (10^6) realm). Nothing in physics is "instantaneous" (not even photons) but you can get close!