Bandwidth limitations on fiber optics in audio

If your standard fiber connection between DAC and transport is bandwidth-limited, how come our home fiber can run gigabytes of data?

[@killacallahan1]

Thanks, Paul, that makes all the sense in the world. And it's Lawrenceville, Georgia. Thanks for all you do, and I can't wait to come to Denver for a tour. this is Callahan, the one that asked you the question

[@michaelbeckerman7532]

It's also important to note here that consumer fiber optic connections used in audio devices are based on LED's as the light source and the audio data is transmitted through mostly plastic cables (with some higher-end TOSLINK cables having some level of glass to them). When we talk about data networking using fiber optics we are talking about using far more powerful lasers as the transmitting light source and we are always dealing with far more expensive single-mode and multi-mode fiber optic cables made entirely of glass.

[@bf0189]

Was going to write this! It's basically a glorified on and off light switch that just pulses quickly. I still use a TOSLINK on my bedroom TV going to a mid fi DAC then to monitors so it still has its uses. I don't need ultra high res on my smaller system 96/24 is more than plenty.

[@ericelliott227]

Thank you for writing this! I love it when one gets a real science based and earth based bit of info in contrast with the BS so prevalent in audio. I would only add that in audio now there is really no reason to go beyond TOSLINK between components and such. Today, we have streaming which is every reason to go beyond TOSLINK, but really only for coming into ones dwelling and their streaming device. It would make zero perceptible difference going to downstream gear, but makes perfect sense for first order source gear.

[@bradtowne2305]

@@bf0189Seems to me it’s just that the investment in the receivers/transmitters has not been a focus of the consumer electronics company. I love Toslink and use it still for most of my devices.

[@bradtowne2305]

It seems to me the entire consumer AV market could benefit from investing in a higher bit rate optical alternative to HDMI, which is a licensed technology and has limited the number of entrants into the AV receiver market.

[@grandrapids57]

Toslink seems is still a standard to be measured against for two channel audio. What's amazing is that it was set so long ago yet it remains.

[@paulkerr9128]

Good explanation around the limitations of toslink and why it has had its day. In the world of TV/home theatre, HDMI replaced toslink and component video cables as the standard connection over a decade ago and I don't understand why it hasn't also replaced toslink in the audio world. HDMI has an industry wide standard so can be implemented on any piece of audio equipment with no compatibility problems and is also a good reason why an older higher end AVR can make an excellent hub for an audio system as it will handle hi res audio sources with no issues. Some even have good internal Dacs.

[@andydelle4509]

True HDMI audio (not these I2S hacks) is quite complicated. Just as with old analog TV, there is a space between each scan line, used to be called H blanking, now it's called HANC. This is where the audio channels along with other high speed metadata is carried. The audio must then be at the video sampling rate, which is much, much higher. So the audio is time compressed and then restored in the HDMI receiving device. The audio samples are written into a memory buffer at the native audio sample rate. As the buffer fills, the samples are read out at the video rate and placed in the HANC area as short data bursts. In the receiver, the opposite is done to restore the audio back to its native sample rate. This means a full video rate clocking system must be added to any audio only device as well as the processing hardware. It's just an extra cost for no real benefit over SPDIF for audio only usage.

[@36karpatoruski]

The standard at our house is dog bites. Transmitted just one at a time.

[@marcse7en]

In the background, some sort of electrical fitting is hanging off the wall, next to the row of three groups of AC outlets ⚡ ... The "S" in "PS Audio" must stand for "Shock?" 🤣 I first used "Toslink" 34 years ago, in 1990!

[@spacemissing]

Toslink connections are pretty good for consumer-grade equipment, but they aren't as precise as permanently connected fiber optics. Imagine it as the difference between trying to see something by looking through a loosely held length of garden hose versus a firmly mounted and stabilised length of rigid pipe.

[@janinapalmer8368]

That analogy right at the end .... are you saying that light velocity changes significantly as it passes a slight curve ..?

[@biketech60]

It was explained to me that the input and output devices are the hang-up . There are glass fiber Toslink cables capable of higher speed if only they had better devices for connection .

[@gotham61]

Toslink recently celebrated its 40th birthday

[@6643bear]

Great and interesting video, regards mark

[@lamarw9901]

The additional problem with agreeing to ditch Toslink is SACD didn't catch on and the non audiophile masses are often streaming at less than CD quality. We audiophiles would love to have and use more bandwidth but, we need to bring the demand to market to make it happen.

[@majicogarcia8417]

I read that the main limitation of Optical is not in the hardware, its companies refusing to send their best signal through it. My old Oppo bluray player matter of factly states in the manual that they are contractually prohibited from sending the best signal via optical.

[@andydelle4509]

We need to keep in mind that a 44.1K or 48K bit stream is not running at 44.1 or 48 khz. The 48K is just the sample rate. A standard audio frame is 32 bits. Up to 24 bits for audio* and 8 for metadata. So we multiply (48k * 32) we get 1.53mhz. 96K doubles that number and so on up to 192K sample rate which equals 6.14mhz. That is video bandwidth (standard definition). So serial digital audio is running in the RF spectrum and thus transmission over wire or fiber becomes increasingly complex. *The transmission frame allows for 24bit audio. However that doesn't mean we always get 24bit resolution. In the case of 16bit CD audio, the lower 8 bits are just ignored by setting them to zero.

[@flargosa]

Even with lower bandwidth toslink some dacs already have processing delay. With 2x-4x the bandwidth dacs might have more issues keeping up with a tv. Many dacs just don’t have enough processing power. of course, if you only usw dac for music, delay in processing isn’t an issue.

[@reestyfarts]

Like the car companies tearing up the railroads. HDMI sells crystalline multi pin connectors to suffocate fiber optics in consumer audio beyond Toslink.

[@georgeballow7028]

Krell connected their pieces with their own method they called CAST. Figure out something like that exclusive to PS Audio with fiber. The added bonus is that once you have it on one end - you need to buy the other end component.

[@hansfriess]

So if the professional companies have to clean the fibre optic cables. It would seem to make sense that it would be a good idea to change out our Audio optic cables every now and then.🤷🏻

[@patellinghuysen]

As a general rule Communication companies clean and inspect fiber optic connections upon turn up of a new piece of equipment or if there is a failure and an existing connection needs to be taken apart for troubleshooting. We do not routinely disconnect customers to clean their connections.

[@air870]

The gradual acceptance and incorporation of I2S gives one hope that newer technologies will become mainstream in audio.

[@andydelle4509]

That's not going to happen on any official basis. The only hope is all the I2S audio product developers would agree on the pinout and electrical standards using the HDMI connector and cable. But I think that ship has already sailed. I2S was never designed or intended as a component interconnect standard. Yes it does work fine for simple audio interconnects but it would never pass the rigid requirements needed for standardization as a cable connected interface. I2S as a component interconnect is an audiophile cult thing. The standard digital audio interfaces AES, SPDIF, ADAT, MADI, all work very well. Another glaring issue with I2S is that it requires four connection paths. That is not a big problem when connecting a transport to a DAC, but whe we get in long cable runs or the need to switch I2S we get into all kinds of electrical problems as well as four levels of switching needed.

[@user-od9iz9cv1w]

It would be great to see a fibre optic cable standard emerge for I2S and to replace clock coax cable. Rigid coax with SMA and U.FL connectors are a pain.

[@tristanjones7735]

No. What would be great is for crystal oscillator companies to stop charging an arm and a leg for a decent clock. Then you could just reclock all the incoming data using any junk connection you want and it wouldn't make a difference. You could use telephone wire as a data connection and as long as the bits reliably made it to the dac, it would sound just as good if not better than any i2S connection out there.

[@mrronenza]

Thanks for the video. What if I have a streamer with SFP switch with SFP LC Module connection ? Is it Toslink ? Thanks

[@AllboroLCD]

Ive wondered this myself. I once thought we were gonna even see an optical video interconnect at some point. Instead they just opted to develop further into copper. In the data world, fiber has a far better latency than copper ever can mind you.

[@andydelle4509]

We do. It's called SDI or HDSDI. It can be run on coax cable or fiber, now up to 12gbs (4K UHD). But's it's only used in broadcast and commercial AV systems. HDMI was built on the SDI standard and may things are similar. But SDI at 12gbs can run 100 feet on coax. 200 feet for 1080p HDTV. Even in broadcast and mastering facility design (which I do) we only resort to fiber if we exceed the practical coax length limit. Fiber is expensive, terminating fiber is a skill that requires training and practice, fiber requires powered hardware at each end which now introduces more 2 points of failure. On HDMI over 50 feet you should convert to fiber HDMI but that's rare. Most residential HDMI runs are six feet or less. It's simply a cost issue yet if you need fiber for long runs, there is a plethora of third party converters which can do that for you. P.S. Fiber transmission is actually slower than electrons through copper wire. It's due the velocity of propagation in different materials such as metal and glass. But as fiber can carry a lot more data per second (bandwidth) than copper wire, it ultimately is faster. We are talking slight differences at around 68% the speed of light so the speed difference is basically irrelevant for almost all applications.

[@TheDanEdwards]

Rarely do these audio discussions cover an important concept: _synchronous vs. asynchronous_ serial interfaces. For example, Internet connections are done over asynchronous serial networks (which is why audiophiles obsessing over internet cables is silly.) *However* , consumer audio digital links, such as S/PDIF, as discussed by Paul, suffer the problems of synchronous interfaces, such as jitter. Bandwidth is rarely the issue in today's audio quality (e.g. Octave Radio sounds great over a low-cost internet connection.)

[@maidsandmuses]

Precisely this. TOSLINK has its limitations yes, due to mode dispersion in the large diameter fibre optic guide used, but S/PDIF is the other side of the problem. You need to go to an asynchronous protocol. This would also solve the master/slave clock synchronisation issues. And yes, audiophiles obsessing over internet cables is silly.

[@jC-kc4si]

The fibers the big boys are using isnt exactly plug and play 'easy'. The connections need to be perfect, levels need to be amplified or attenuated. An inspection probe should be used to inpect the fiber for defects and cleanliness. Also, tons of heat generating electronics are needed to do all the magic to cram so many bits into such a tiny piece of precision manufactured glass. Yeah, toslink plastic cables are 40+ year old tech than anybody can connect in a few seconds without any of the tedious labor that is required to properly install real fiber optic cabling. Can you imagine audiophiles probing and cleaning their fibers regularly?

[@seedney]

Do we using some technologies like in communications (ISPs) does? - I'm intrested in - TCP comparing to UDP in audio world (in sense of data correctness/correction/inspecting/resending)? TCP - machines know that data is send and recieved uncorrupted, resends signal if one link is down through another vs. UDP - send and don't care about anything other than speed...

[@alex_stanley]

So, whose butt do we need to light a fire under in order to get a modern fiber optic interconnect standard?

[@stefpichette7742]

Is that a rel tx5 in the back

[@sidesup8286]

Can fairly high wind create a danger to your cd player if it is playing? We are having 50 mph winds and the electric lines are swaying in the wind. Many years ago, my cd player went black as they set off some fireworks about a mile away during a celebration. I figured they must have been set off too close to some power lines and if fried my cd player. Unlike it was a grand coincidence that my cd player quit right during the fireworks.

[@AA-ws3vd]

My 50FT. HDMI cable in the walls is optical, so that's the good kind?

[@doylewayne3940]

Another reason to hold off my system upgrade until they dump Toslink and change to a fiber connection standard Paul.

[@Pure79er]

He Paul- what do you think about Electrostatics? I bought some and iam not happy. Matthias from Kiel, Germany.

[@JoeSrutowski]

I hope the same people who butchered those outlet and trim plates don't build your products

[@harackmw]

Fiber loosens up that low end, dull the highs, sounds terrible and not neutral at all but will keep you regular.

[@razisn]

lol, what have you been swallowing?

[@chungang7037]

@@razisn an audiophile daily diet! lol

[@harackmw]

@@razisn Well! that is a very personal question...🤣

[@ZeusTheTornado]

What the hell are you talking about

[@harackmw]

@@ZeusTheTornado Fiber, what else?

[@manitoublack]

can send high bandwidth data over fibre in the home. HDMI over fibre is the way to go for long runs (+5m) in the home for 48GB/s. Can do 48GB/s reliably over copper of

[@christophmartin5381]

Well 24bit 96khz or even more, no problem with Toslink. Where is the limitation? I know there are other digital standards which need higher bandwidth. But for simple stereo...

[@endrizo]

nobody will hear any difference. toslink capabilities were 40 years ago beyong human hearing capabilities. anything more is mere markering wanting your money

[@andydelle4509]

The limitation for digital audio is simply that there is no standard to build to beyond TOSLINC. We have standard interfaces like AES which work just fine. Also when we go above 96K, the limited bandwidth of TOSLINC using plastic fiber and visible LEDs is sketchy. And as audio is becoming packet based over Ethernet, there's no incentive to build a better direct digital interface. Very soon Dante will rule the professional audio world and SMPTE 2110 will rule the video/audio sector. Yes even SDI and AES are quickly becoming obsolete.

[@jos5067]

24 bit / 192khz is the limit for Toslink.

[@julesvreug]

If want to do long runs of cable eg HDMI, USB there are now Fibreoptic options and not that expensive either. I would only connect a 4k projector using Fibre optic HDMI cable as anything else it will be a hit and miss just dont go out and speend hundreds of $$ on HDMI cables and repeaters/boosters it just aint going to be reliable! esp if 4k60 with eARC (Dolby Amos audio etc). Pitty Philips/Toshiba isnt really inventing anymore or someone else come up with fibre optic standard as interconnects between devices could be so much better and reliable than HDMI, RCA etc etc.

[@whome8192]

Cheap, plastic fiber. + Cheap toslink drivers = low bandwidth and short distance.

[@shadowofpain8144]

Seems moronic to not put something faster even if it only works with your gear at nearly same price, just gives one more reason to buy your gear. And it cant be that hard to have an adapter to make it backwards compatible with tos.

[@stephenstevens6573]

The larger manufacturers of high end audio dont want a simple standardized method to be implemented. Its simple economics. With all of the community seemingly embracing streaming as an acceptable medium, the hocus pocus of "audiophile" quality equipment, ultra high dollar cables, interconnects etc....whole industries would effectively be in the wind. Its coming...they know it, we know it, but nobody seems to be in any hurry to see it come to fruition.

[@endrizo]

limitations?? 24 bits 96khz and 120 db s/n ratio is more than enough. you wont hear any difference when surpassing that... may be children can but older than 40 years old you wont... PERIOD. Nobody will hear any difference. toslink specs were 40 years ago already beyong human hearing capabilities. anything more is mere markering wanting your money. just relax and enjoy.

[@chungang7037]

thank you!

[@edfort5704]

Have you still not heard any DSD recordings yet? Prepare to have your audio-worldview shattered once you hear a few good DSD songs. Even a few seconds of well recorded bass in DSD will open that window. Try it. The funny thing is that Toslink S/PDIF actually can pass through some incredible -sounding audio in DSD, even DSD256 and beyond, even though the standard officially doesn't apparently support its bandwidth. The DSD music I've heard with my own ears passing through TOSLINK S/PDIF between my PC's MB and entry-level but good amplifier is unlike any other sound that has ever come out of CD audio. You want the short explanation why 96kHz samping rate is not enough? It's because the elephant in the audio industry's room is that we can hear many different sound frequencies concurrently and they all have to be sampled together in a sum of samples in order to capture them and play them back.

[@chungang7037]

@@edfort5704 Which recordings would you suggest?

[@edfort5704]

@@chungang7037 Don't have much time to reply long right now, but listen to whatever DSD content you can find since it's not like you can find much right now. A little secret from me: most if not all DSD files I've heard so far are actually captures from Vinyl, not native direct DSD recordings. That's still enough to blow your mind as to the audio qualities and capabilities of DSD. There is hardly any studio out there yet who produces native DSD content. PSA's Octave Records are a rare coin and have barely just begun producing stuff, so you can try with them if you feel like it.

[@chungang7037]

Is this really a thing? It reminds me too much of the argument that usb cables sound different.

[@ford1546]

It's such a shame and sad that no one has come up with an improved version of toslink MANY years ago. It wouldn't have been that difficult. Another thing is bluetooth which to me a mystery that it has not become faster. bluetooth is so incredibly slow! Bluetooth is so good but such an incredibly slow way of communication. It is also a shame that all units use 10 meter radio transmitters and not 50m or 100m

[@j.m.harris4202]

Quantum Computation and Communication doesn't use Bits or Bites and Rules the Ether from Darkness! AI combined with Quantum Computers will come to the Conclusion that Ears and Humans are no longer necessary! Thus no more need for HiFi! 🤔