Optical Cable vs. Digital Coax?
 

For a PCM connection from a streamer to an external DAC, is there any benefit of TOSLINK vs. digital coax?

I assume both carry the same S/PDIF bit stream, but I seem to recall reading that there could be some kind of problems with TOSLINK, bandwidth or excessive jitter maybe? Are there other issues besides available outputs or inputs to consider?

From a Relative Newbie -- Clark2

In my system coax or aes/ebu sound better.

TOSLINK (TOShiba LINK) is very old standard, dating back to the early days of CD music. It has bandwidth limits, but can transmit lossless 2 channel audio. Fiber cable (typically plastic) does offer electrical isolation. In the end you are converting electrical to light then back again, so poor implementations may introduce jitter. The cable is cheap, small, and flexible - those are the drivers.

For most systems, coax cable is a good choice. Of course, there are well-engineered TOSLINK solutions out there.

Thanks, Both -- I'm currently using digital coax between my BlueSound Node 2i streamer and my Topping D50s external DAC -- not really high-end gear, but good enough as long as it works.

Recently a problem has developed (after I replaced a Node 2 that failed with a brand new Node 2i, and admittedly, after I got a new preamp, power amp, and high-end speakers and started spending a lot more time streaming from Qobuz) with occasional "crackling" over the music and brief dropouts. This problem is very intermittent, so difficult to track down the cause. (I don't even know yet if it only occurs on very-high resolution tracks -- I have played an occasional 24-bit by 192 kHz track from Qobuz.) I've heard rumors that some folks have had problems with the coax input on the D50s, but they may be just that.

Just wondering at this point if the coax link might be the cause, but from what you say, it's likely to be a better choice than optical. (The Node 2i does not offer a USB output.) -- Clark2

Easy enough to try a piece of optical cable in lieu of the coax- get a budget cable for this purpose. But the symptoms you describe are hard to assign to a digital cable.

Dear clpetersen -- Points taken. I'm looking into other potential culprits as well, notably my router. At least you didn't tell me that the bandwidth of optical fiber is too low to handle HD PCM data, which I've seen on some less reliable sites, or that the TOSLINK implementation on the Node 2i is no good... -- Clark2

When Toslink first started, most of the transmitters and receivers were only rated up to 24/96 so it couldn't handle 24/192 material reliably.

Coax should be able to handle 24/192 more easily. But you'd really want a proper 75ohm coaxial cable. Many RCA cables are only 50 ohms.

One thing I did notice using a BlueSound Node was that it was very clunky with varying bitrates. It would cause issues with slight pops or dropouts between songs if the sample rate changed.

In my experiences, coax (75 ohm) bested toslink. Differences mostly were not night and day and depending on the recording some non existent. Also little difference if any between an Amazon special and higher end toslink.

Your mileage will no doubt vary.

John

Thanks Again, All -- I have noticed other evidence that the router feeding my Node 2i is defective, so I'll be installing a new one this weekend. After that further troubleshooting of the digital interconnection may or may not be necessary. Best Regards -- Clark2

I'm in need of further advice from you streaming experts. I did replace the router, and it appears to be working great -- upload and download speeds consistently over 400 Mbps over the wired Ethernet LAN that I'm using, and ping delays around 10 ms. I also did a factory reset on the Node 2i, which might have eliminated the "crackling" that I reported earlier, but not the occasional brief dropouts. You folks have much more experience than I, so maybe you can help me sort out the remaining issues:

This morning I'm listening to a series of 24-bit by 48 kHz cuts from Qobuz and have already heard at least two brief dropouts. Note that this bit rate is a factor of 4 below the top-rated speed of these devices and that even a 24-bit by 192 hHz stream would require less than 10 Mbps of Internet speed! It seems I may have a much more global problem that I had suspected. I'm beginning to wonder if all of my problems are coming from short-term dropouts in my Internet service (or a local Qobuz server). New questions arising out of this speculation:

1) Is there a way to test an ISP's streaming performance over long-enough times to detect and quantify these very occasional dropouts? (I suppose this might be either a piece of software or a "black box" that one connects to the LAN.) First and foremost, I need to determine the true origin of my problems!

2) Is the buffer in the Node 2i too small to cover the Internet dropouts that I might be experiencing? I've seen no specs on buffer sizes in BlueSound devices, but I suppose there's a compromise to be made between cost and dropouts. Are other streamers designed with larger buffers for this purpose? Or are there "outboard" buffers that can be purchased to ameliorate this kind of problem? (I suppose the ultimate solution to ISP dropouts is to purchase and download to hard drive all the music I want to listen to, but this is expensive, cumbersome, and defeats the main advantage of streaming.)

Explanations or suggestions would be most welcome. -- Clark2