Why does optical suck so much?

My uneducated guess is that its in part to the fact that the signal is transmitted in multiple.. I don't know the word.. formats? It seems similar to how some S/D DACs toss aside the original signal/samples and provide new ones. The original electrical signal is gone before it even leaves your PS4 as the PS4 is outputting pulses of light. And that light cannot be input directly into your DAC chip so a new signal is made again on the input. If nothing else you have two more components than you would have had prior which need their own clocking hardware; there are more points of potential failure.

There is a company in the Netherlands called EC Design who for a time last year preached that optical was the superior mode of transfer. You can read about it in the review of their Mosaic T DAC. The gist of it was that optical offers galvanic isolation; it is worth noting that not 6 months later optical is not even offered on their DACs. Making another uneducated guess here.. I'd say as soon as they found the means to isolate USB they jumped ship.

 

I think this article explains many of the issues but it's abit technical talk.

http://www.audioholics.com/audio-video-cables/toslink-interconnect-history-basics

 

I don't think it does suck, and if it sucks at all, it certainly doesn't suck so much.

I used to use it as my digital i/o method way back then. In those days, USB was thought to suck even more, which was probably a hangover from USB1.0, which did suck. It was my only digital i/o, so no direct comparisons, but I was doing quite a bit of i-ing and o-ing back then, and once I found the right sound card (RME) for me (which sounded far better than the Cyrus CD player I had then) I was happy all round.

I have only used optical once in recent years, which was simply to compare the different inputs to an on-test DAC. This was just my motherboard toslink output and... it sounded the same as the USB. To me, at least.

It may be important to mention that I never play music at >24/96. Beliefs aside, I don't have a DAC which exceeds it any way. Those who do need to play the higher-sample-rate game may well find that optical does not suit.

Here's my bottom-line belief about why audiophiles really hate optical. It's plastic.

 

Optical Toslink has typically exhibited higher jitter than its electrical counterpart. So, to the extent that devices being connected rely upon low interface jitter, then optical might "suck" in comparison to some alternatives. Optical cable bandwidth is also limited and might not be suited for hi res audio (but I'm not sure exactly where it peaks out). However, at one point, I had seen proposals for future optical USB cabling specs that overcame previous bandwidth limitations of Toslink.

Edit: Oh and optical performance can be affected by the cable quite easily. But it's still my somewhat educated guess that suitable cabling can be found relatively inexpensively.

 

This has been my experience as well, since in my case I have no noise/power/etc issues with my USB connection, so I didn't really notice much difference as compared to toslink. I think when all things are equal and there are no major problems with the given connection type, in theory there *shouldn't* be much difference. To me, the advantage of optical would be if you had a ground loop or other noise problem with USB, it would give you another option to bypass that particular issue in your system. Or maybe if YOUR particular OS version / motherboard / other peripherals / etc combination has a flaky driver for either USB or optical, than one might be better / more stable than the other in YOUR situation. For instance, maybe if you have a monster graphics graphics card or other devices with high speed fans that are creating noise that is picked up by the USB connection, then optical might sound better in that case as it should be immune to that type of noise.

I think it's unfortunately another one of those "it depends" situations where there is no "best" answer for everybody.

 

I agree with your entire post. Also, the "optical USB thing" somebody mentioned is developed for electrical isolation.

Bottom line is that there is nothing wrong with transmitting data as pulses of light. This post is going to travel thousands of miles in that way, and some of the music we stream comes a fair distance.

Curious thing is that that data is going to be sent over some very expensive fibre and networking equipment, whereas toslink, as far as I remember (I think I first encountered it on portable mini-disc players) must have been developed as a fairly low-cost system, with relatively low-cost materials, connectors, etc etc. We are not going to be able to pump gigabits/second down it. It has its limits. Of course, so does USB2.0, although they exceed audio requirements, even for high-sample-rate music, to the extent that people are being pretty slow to even bother with USB3.0 for audio --- although its great potential is the additional power-carrying capacity.

By the way: bend toslink cables through too small a radius, even though not sharply enough to break or permanently bend them, and they will sound broken.

 

Same with CAT cables. Misalign the twisted pairs and your ethernet suddenly become unstable. Not so bad now that everyone has jumped on the Wi-Fi bandwagon, but I like those gigabit speeds which Wi-Fi still can't attain without some serious multiplexing.

 

Everything up to the point(software depending?) the signal is sent to the DAC has error-correction. Internet especially has compensation for lost packets and the ability to re-request data which never arrives. Files have a defined structure even if the bits which make them up are scattered across your drive(and this is where defragging comes in to speed up reassembly.) I have to imagine if digital audio was able to correct for errors/timing a lot of these discussions would be redundant. I'm not really sure why no DAC manufacturer has implemented this yet. You would lose out on sync with video content, however this is already the case with DACs which employ buffered input. Of course the next step would be RAMdisk or flash memory where you'd preload the next album to play and avoid cable interaction entirely. Give you a taste of the vinyl ritual.

 

Well in the case of USB (although this is a Toslink sucks thread) I think (A) most DAC manufacturers aren't developing the USB front end for their DACs from scratch. They're using and/or integrating ready-made solutions. It only makes sense. And (B), again in the case of USB, the isochronous protocol doesn't allow for retries... In some ways, it wouldn't really make sense. But then, bit errors aren't really the problem. So you might as well just drop the CRC on the floor. Timing is a different issue from bit errors and CRC. And what you mentioned is what I was saying in the USB gizmo thread the other day... Buffer the data (you don't need to buffer the whole song) in order to decouple the source's timing inaccuracies from the device and suddenly I think things get a lot better. I suspect the Mutec USB device, among other things, is performing this exact function... but it's only a guess.

 

Timing was always the excuse. Audio and video, obviously, are real-time experiences, but the delivery methods and protocols are not.

My hobbyhorse... Forget the way we have done it in the past. Ethernet is now more-than-fast-enough (at least for audio) and there is no reason it should not be implemented cheaply, ie same cost as other network devices, not audiophile-inflated stuff. It is not exactly a new idea, either: how long is it since the first Squeezebox?

 

European SBAF's can correct me, but in Europe CAT cables are used as general signal carriers and not just for ethernet. I seem to recall that CAT/RJ45 connectors are found as interconnects and sometimes used as speaker wire there.

 

It's audiophoolery. In my not-so-humble opinion, at any rate.

They are engineered with just one purpose in mind, and anything else they do, they do just because, hey, it's copper wire, and copper wire conducts electricity, and conducting electricity is all that is needed for many audio purposes, if they don't need shielding. And that's the very thing the audiophools love to deny.

Network (CATn) cables for other purposes? Sure... if all you need is some thin wire. Might even work for christmas-tree lights.

 

SPDIF cables were never that reliable for me. AES ones tend to be tanks though. Also lots of Macs and old gear have problems outputting anything above Redbook.

 

Macs have no problem at all outputting high res over usb and do quite nicely with 96khz via toslink.

 

A lot get spotty with the higher bit-rate optical stuff but yeah USB is fine.

 

I don't think the problems are inherent to fiber optic. Afterall, it does surpass copper when transmitting data over networks at much higher rates than 192khz. Yet for some reason toslink can only do 96khz reliably.

I think when it first came out it was the best but since then the tech has stalled with no real development of better optical solutions. Which an investment like that would lead to nowhere because RCA and BNC can already meet those needs competently.

Still, I think it's worth revisiting because it eliminates ground loops and is not effected by EM interference. As the daily life gets more noisy (wifi, Bluetooth, 4G, etc.) old fashioned coax might not be enough.

 

Optical data transmission can use different data transmission methods, like network traffic vs spdif which is used in most optical Toslink connections. I think we cannot expect too much from a $1.49 Toslink transmitter and receiver using leds coupled with some low grade poorly polished and terminated plastic fiber.

What did hold promise and performed well back in the day was ST glass terminations used on some high end dacs like Wadi and Bel Canto. Not sure of any of this is relevant today when you have alternative connection methods for digital that can perform as well or better than Toslink.

 

Well, the isolation provided by the optic link sure is beneficial when connecting modern noisy equipment (TV, Blu-Ray players, consoles) to sensitive audio gears.

I've been playing with ST Fiber (added a ST output to my Digi+ Pro) to connect the older DACs (PS Audio UltraLink II, Theta Basic IIIa). It's f un.

 

Well stated Clem.

And what I think we sometimes forget is what happens to noise in an environment after the dac gets ahold of the signal?

Power line to dac, power line to pre, power line to amp, RFI from computer equipment located near your analog equipment, interconnects, etc. all full of your and your neighbors appliance noise, wall warts bleeding their ultrasonic noise into your wiring and circuit box, cell rfi, wifi rfi, radio rfi, about to tap out power transformers on the grid, etc.

True no ground plane crap coming into the digital inputs, but a whole host of other crap to deal with after that. Breaking one ground somewhere in the system will not cure all, that is for certain.