DIGITAL OUT: Optical Cable vs. Coaxial Cable

Fwiw, I have found that the HDMI connection from my decidedly consumer level Panasonic BDP provides better sound than the Toslink for two channel redbook playback, using roughly equal priced ($50) cables. The Toslink is plactic fiber I believe. I didn't know what to attribute this to since there are so many variables including quality of the electronics in both paths on both ends. The Arcam AVR 400 receiver I use in this system may have better implementation for receiving audio signal through HDMI, dunno.

The easiest thing I can control are the cables. I was skeptical of differences in digital cable quality until I fooled around with various consumer brands of USB cables from Radio Shack and Frys for my computer audio system at work and found a clear difference in sound quality (HP branded cable won). I will try some of the cheaper medical instrument high thread count glass Toslink cables and see how they compare with the "budget" Audioquest I'm using now, and see what I get.

Hello,

I too am suspect about the transfer of zeros and ones. Analog is an entirely different matter though. While I had difficulty believing that a coaxial cable could beat a direct digital transmission from an optical I was proven wrong recently by a simple A-B comparison between the two. The comparison was of similarly priced cables from inexpensive vendors on EBay. My inexpensive coaxial cable delivered an amazing difference in bass depth and information. I was proven wrong on my system. Coaxial is superior. I'm convinced that when I purchase any new equipment I will do the A-B comparison again so that I don't go for another ten years on presumptions rather than proof.

Sincerely,

Al makes a good point. It is gear dependent. I use a Benchmark DAC1 partly because the claims by the manufacturer and most reviewers have indicated that it minimizes any jitter interface issues. Interface jitter is a problem but the right gear can eliminate the cable uncertainty issue. I have said this before - blame the equipment or the combination but not the cables.

Has anyone seen this Monster Cable Commercial?

Doesn't anyone get the suspicion that there are huge margins in audio cables and huge sponsorships (like sports gear)?

After all, cables are all made by cable manufacturers and not audio cable companies (who just place bulk orders to ordinary cable manufacturers).

Anyone get the idea that the magazine advertising revenues from audio cable companies might be huge?

I am rather suspicious of the justification for $1000's worth of cables. I suspect many reviews have a vested interest in maintaining the market for high priced cables and the advertising revenue it brings in.

But hey, I'm just a dumb engineer with tin ears...

I found the Wireworld SuperNova 5+ to be as good as very good SPDIF in my old rig. I do like the electrical isolation Toslink provides - I think it makes an important difference.

The other point is strictly practical - you can get a 3m Wireworld for the same or less as a good (but not insanely great) 1m SPDIF.

There was no misunderstanding to be sorry for, Neil, at least as far as I am concerned. :)

I assumed that you were referring to impedance matching and maintaining waveform quality (so as to minimize jitter), and that is what I was responding to.

Best,
-- Al

When I referred to "variations in the 75ohm interface" I meant variations in the ability of different types of connectors to maintain the integrity of the RF signal across the interface; and not the quality of construction. Sorry for the misunderstanding.

Of course I suppose there can be variations in 75ohm interface quality too. For instance, my friend Larry thinks coax is best, but ONLY if it employs BNC (bayonet) connectors (as opposed to RCA connectors.)

That would be highly system dependent, as it would be dependent on the jitter reduction capabilities of the dac (if any), the risetime and falltime of the output signal from the transport or other digital source, the degree of impedance mismatch between cable, connectors, and interface circuits at both ends, and the length of the cable (which affects the timing of reflections and re-reflections caused by impedance mismatch; 1.5 meters is generally considered optimal, shorter than that non-optimal).

See this paper: http://www.positive-feedback.com/Issue14/spdif.htm

And this and other threads here at Audiogon: http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1237611683

Given these kinds of system dependencies, and others which most likely exist in the case of optical connections, I think it stands to reason that experiences and opinions will differ on the op's question.

Regards,
-- Al

Richard, I agree there are differences in Toslink cable construction; but I wonder if you compared the MIT Toslink cable with an equally "better" metal one?

My earlier point was that Toslink performance can be pushed only so far until it runs into the limiting factor of the transceiver units. A friend of mine who used to be with Wadia explained that the most expensive Toslink transceivers cost the manufacturers maybe $5 - $15 while the cheapest AT&T transceivers start around $100!

Of course I suppose there can be variations in 75ohm interface quality too. For instance, my friend Larry thinks coax is best, but ONLY if it employs BNC (bayonet) connectors (as opposed to RCA connectors.)

i would have agreed with nsgarch two weeks ago but when i changed optical cables it was night and day. the only explanation could be the cable itself. there are allot of discussions on this forum and others about whether quality of either digital cables matters and i never knew what to believe. now i have proof and am quite frankly surprised at the outcome.

The main reason Toslink is crap has nothing (or VERY LITTLE) to do with the cable quality. It has to do with the cheap transceivers (the device you plug the cable into at each end) used in Toslink systems. It's convenient and sometimes necessary when it's important to electrically isolate equipment from each other, but I agree with rcrerar that a good 75ohm will outperform any Toslink, no matter what it's made of.

Glass fiberoptic cable (AT&T - ST) is another story altogether, but it's found only on the most expensive consumer digital equipment (like Wadia, for instance.)

there are many factors to both including length, materials, design quality, associated equipment etc. as with most choices it will take experimentaion to know for sure. i just switched toslink cables on my dtv dvr to theta casanova and there was a marked difference. i would not have guessed this before. the new cable is an mit avt1 and is available through their discount site for around $50 if you chose to go that route. best money i have spent for a long while. i use a mit reference coax digital cable from my dvd to pre/pro. there is allot of good info on this issue on wikepedia.

A well made coaxial cable is more durable than a glass cable so if you change or move your equipment rather than place and forget, coaxial is better. A true 75 Ohm quality cable is held to a reference whereas Toslink can be variable in quality from cheap plastic to expensive glass. If you believe that "bits is bits" then it doesn't matter. I prefer coaxial. Also, the connectors are important, so look at the way the cable is fixed to the connector. A solid cold pressure weld is more secure.

The large majority of Toslink cables use a plastic conductor that can compromise their performance. There are some Toslink optical cables that use a glass conductor which is supposedly much better but I haven't tried one. It has been my experience that a high quality true 75 ohm coaxial cable will easily outperform the best optical cables I have tried. I also find there are significant differences in sound between different coaxial cables. This will depend a lot on the dac and transport you are using.