Regarding a couple of the questions above about the traditional "optical" ports on audio devices -- this was discussed a little bit earlier. As one poster put it: "Different optical we're talking here. The topic is on ethernet over fiber optic, not TOSLINK over fiber optic."
Also, I questioned some audio manufacturers about this recently. Here's what they said (starting with Small Green Computer):
Question I emailed to SGC: I was curious why other audio companies don't go the
optical route, so I did a little reading and stumbled across some articles that said
optical is more limited with regard to high-res signals/files. So, what is the highest resolution file the OpticalRendu can handle and faithfully pass on to the DAC? The highest res files on Qobuz are 24/192. Does that pose any problems for
optical?
Answer: Other companies are behind in technology. With 18 to 24 month design cycles it will be a few years before everybody else goes
optical. You have to be VERY careful and read closely. The word "
optical" in the old world refers to SPDIF
optical. which is very limited.
Optical Ethernet has no limits. We support every rate available on any DAC in the world. As of today that is 36/384 PCM and DSD512.
Question I emailed to Baetis Audio (which makes customized music servers): I have another question about Baetis servers: can they come with a Toslink out, capable of transmitting high-resolution files (at least 192kHz/24, and preferably higher) to a DAC with a Toslink in? It seems to me that fiber optic cable would completely solve the problem of line noise (from "dirty" power, radio frequencies, etc.).
Answer: Many of our systems do come with a TOSLINK out capability. However, these are not subjected to the clean signal that our daughterboard’s SPDIF and AES provide. While in theory an optical transmission of audio data is great, the implementation of the TOSLINK standard is not so great. Many DACs are limited to 96KHz via TOSLINK and 192 is the absolute maximum of the standard, I believe. In practice, our Coaxial SPDIF and AES is a MUCH better option.
Question I emailed to Berkeley Audio (maker of a very highly respected, high-end DAC): Hello. Regarding your flagship DAC, does the TOSLINK port support 192kHz/24? And is it the best input for sound quality?
Answer: In answer to your question; optical Toslink has limited bandwidth which results in slower data transitions which in turn increase effective jitter in the data receiver. With an excellent cable and source device Toslink can sometimes pass 192kHz but not reliably. 96kHz is a more realistic limit. We provide a Toslink input primarily to allow connection to devices such as AV receivers without coupling noise from them to the DAC through a ground connection.
Balanced AES/EBU is the best format for sound quality. It is also preferred over coaxial SPDIF. The primary reason is that it has 8 to 10 times greater voltage swing than coaxial SPDIF which results in less effective jitter in the DAC’s data receiver output.
If possible, use a 1.5 meter long AES/EBU cable. We recommend a 1.5 meter length because it is short enough to have low capacitance providing fast data transitions and long enough to reduce the negative effect on data receivers of reflected energy caused by return loss in real world transmission lines that use connectors with impedance discontinuities.
