Diablog: Optical vs. Coaxial Fracas

Who are we? Why are we here? Is that enough existential questioning for you?

We are the Audio Diabloggers. Our job is to stand in for Mark Fleischmann.

Mark Fleischmann? Who's he?

He's that little bald man whimpering in the corner.

Huh. What made him so glum?

He's the audio editor of Home Theater Magazine. And he's just been told he has to update this blob, I mean blog, as often as possible, in addition to writing reviews and heaven knows what else.

Well, that doesn't seem so bad. He gets to listen to music and type for a living. What is a blog, anyway? Isn't that the sound writers make when they vomit?

In many cases, yes, but it's also a priceless opportunity for Mark to express himself, or it would be if he were actually writing this. However, he has too many boxes full of gear to pack up today, and pretty much every day, so we're picking up the slack. Essentially Mark has split into two separate personalities—us. This is what he gets for giving up his happy freelance writing career and joining a corporation. Entering the corporate world has deepened his innate schizophrenia into a deep and frightening chasm.

I have a feeling I'm going to hate this.

No, actually, you have the fun job. You get to question, challenge, and deliver acid commentary on the foibles of the audio industry. Mine is the tough job. I have to absorb your insults, discuss how inputs and outputs work, get inside the mindset of manufacturers, and Explain It All.

Bor-ing! OK, what's our topic for today?

Well, since we're already 250 words into this, I figured something small would be good, one of those "world in a grain of sand" topics. Namely, coaxial versus optical digital outputs, and why audiophiles care about them.

What could be possibly be interesting about that?

Well, for one thing, the sheer amount of heat generated by the topic. Back in the early 1990s, when separate digital-to-analog convertors and disc transports were new and novel technology, Mark spent some time listening to them. He was writing for Rolling Stone at the time and had no trouble getting some product together—three high-end DACs by Meridian, Theta, and Enlightened Audio Designs. He went back and forth among them, trying both the coaxial and optical outs, and while he had no trouble identifying the distinctive sound of each manufacturer's DAC—and ended up buying the Theta—he felt the difference between the coaxial and optical outputs was so tiny as to be dismissible. Years later, in the middle of a story about cable, he opined that there really isn't much audible difference between coaxial and optical outs, and you should have seen the hate mail that poured in!

To me, that just proves that audiophiles have too much time on your hands. Are they really that different?

Well, they both pass a S/PDIF signal.

Did you just spit at me?

No, that stands for Sony/Philips Digital Interconnect Format. It's used for PCM audio from your CDs, Dolby Digital and DTS from your DVDs, and one or two other things.

Those are all digital formats, right?


Isn't digital audio perfect?

Heavens no. Ask anyone who owns a turntable and still uses it. Also, even within its inherent limits, a digital signal can get messed up in lots of ways. Some of them, like jitter, are clock-timing errors...

You've lost me. If it's a digital signal going through each kind of cable, isn't the end result the same?

Not exactly. An optical cable transmits the signal as pulses of light, while a coaxial one passes the signal as pulses of electricity. The question is whether the difference between the two is audible. Having done his own independent listening, Mark says one doesn't sound that different from the other and that's why everyone hates him.

No wonder he's cowering over there. Man, he looks really sad. Should we offer him a glass of water or something?

He'll keep. What Mark ignored—and his readers pointed out, at length—is that each type of cable has its own particular strengths and weaknesses. Coaxial has higher bandwidth. And optical is less prone to hum, because it breaks up ground loops, which happen when interconnect and power cables set up a closed circuit. So both sets of critics made some valid factual points.

If he thinks they sound the same, does Mark use the two types interchangeably?

Well, no. He favors coaxial cables because the back of his rack is a busy place and the plastic filament in a Toslink optical cable is fragile. You kink it, it stops passing the signal.

But there's that hum thing you mentioned. Even I can hear that sometimes.

That isn't a problem for Mark because he uses a power-line conditioner that isolates his components enough to keep ground loops from forming. But once in awhile a piece of gear he's reviewing runs out of coaxial outs and he has to whip an optical cable out of his collection. His favorite brand for that is Vampire Wire.

What a pretentious thing he is. But he says it sounds OK.

He does.

Well, as our shrink says, I'm afraid we've run out of time. Just one thing that niggles at me -- shouldn't we tell our readers whether we're a male/female couple, or two guys, or two women?

Let them project whatever they want onto us. Some things they're destined never to know.

Mark Fleischmann is the author of the annually updated book Practical Home Theater. For links to the latest edition, visit www.quietriverpress.com.

John Kosak's picture

You mention a line conditioner briefly in your blog. Would it be possible to devote an entire blog to this subject? I have what I consider to be a nice entry level home theater set up. It includes a Denon 3805 receiver, a Denon 2910 Universal Disc player, my Dish 811 HD Satellite receiver and my Mitsubishi HD TV. Currently these components are all plugged into a Monster power strip. My questions are, in no particular order: How much conditioning do I need? How much EMI/RFI Noise filtration do I need? Is 60db from 100KHz to 2MHz good? Does it mean anything? What would benefit my system more, voltage regulation or line conditioning?Thanks in advance for your consideration.

Mark's picture

At minimum your equipment needs surge supression as protection from spikes. Products that isolate signal sources also help by preventing ground loops which cause hum. I use Power Wedges from Audio Power Industries though my firsthand frame of reference doesn't extend beyond that. I can only suggest reading reviews (including several on this site) and Googling.

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http://www.seminarprojects.com's picture

I use Power Wedges from Audio Power Industries though my firsthand frame of reference doesn't extend beyond that. I can only suggest reading reviews,.

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