Adjusting focus

January 19, 2023
 by Paul McGowan

Knowing where to focus one’s attention is often difficult in our technically complex world. Take, for example, the case of fiber optics.

We know that galvanic isolation can make a big difference in digital audio. Any owners of the new DirectStream MK2, with its ability to switch on and off the isolation of every input and output for best sound, can attest to the benefits of customizing levels of galvanic isolation.

So, it should be no surprise that fiber optics is one of the easiest means of galvanic isolation in digital audio. Sending digital audio data over a piece of plastic in the form of light waves turns out to be as perfect isolation as one can get.

And yet using a TOSLINK fiber optic cable is a sonic step backward (even compared to lowly coax).

What gives?

The problem with TOSLINK isn’t its lack of isolation feature. Instead, it’s a problem with sacrifices.

What did you give up to gain the benefits of isolation?

Bandwidth and quality of signal transmission are severely compromised in the mainstay implementation of TOSLINK.

You gain the benefits of isolation at the expense of bandwidth and signal veracity.

Fiber optics, when done right, are wonderful sounding and without compromise.

One must always adjust the focus on where to point one’s full attention.

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23 comments on “Adjusting focus”

  1. My 20 (!) years old TacT Millenium amp can handle 24/192 on its optical (Toslink) digital input. No problem with audible bandwidth effects. The MK3 version lacking the Master-Clock output for the CD-transport sounds better than the former MK2 version with Master-Clock output. And today you can get simple reclocking adapters even for Toslink.

  2. I seem to recall electrical or galvanic isolation became popular around 2015 or 2016. I took the advice of Andrew Everard and got a $50 old Cisco SFP switch from eBay and put in fibre cabling. I still use the cable, from my modem to my server/streamer.

    The other thing was the launch of the Marantz SA-10 in around 2016, a digital player that was the first to use their new SACD drive that PSA now uses, galvanically isolated everywhere and shielded everything in vast amounts of copper plate, including the whole back panel. I’m not sure it was sold in the USA. It was expensive, £7,000, and soon after they brought out one for half the price, minus all the copper. They still make the SA-10. I think their aim was mainly Japan where silver discs still have a very big market, and also Europe.

    It is a shame that so few products have SFP fibre ports, virtually none, probably because it’s not really a domestic product, but it is very effective and very cheap. The Sonore brand is all based around fibre, but not cheap at all.

  3. There are definite advantages to having the transport & the DAC in the same box.
    Both sections connected the best way possible, internally, with galvanic isolation 😀

      1. That may be the case, but the SA-10 and its descendants have extensive galvanic isolation. This has followed through into their current range. By isolating each section, they figured people would buy the units as streaming DACs even if they didn’t spin discs, knowing the disc section was isolated. Very good performance at a very accessible price-point. It’s a strategy that worked as the 30 and 40 ranges have by all accounts been a huge success.

    1. Billk I had the AT&T output on a Mark Levinson 31.5 connected to the input of a Mark Levinson 30.6 DAC and it provided some of the best sound I have ever enjoyed. I agree it is very lamentable this connection was used by so few manufacturers.

  4. I have always been skeptical of toslink or other ways of transmitting the signal over light rather than keeping it as an electrical waveform on wire. I know implementation is everything, but intuitively the idea of adding a transducer to convert to light, then adding another to convert back to electrical seems like a great way to add nonlinearities and distortion.

  5. I work with light everyday of the week.
    Its ability to transfer data is unrivaled.
    In fact it’s pretty much what the telecom industry relies upon.
    I’m not a fan of plastic fibers.

    Regarding shielding…. I saw a link from a friend about some new material that is being developed. It’s looks pretty cool. (Thanks Stimpy2)

    For anyone interested here it is.

  6. Would be nice if a new fiber optic cable standard having better transmission bandwidth (enough to do DSD1024, just in case) and better quality. I’d rather see this type of connection catch on than another glorified “USB” or “HDMI” in the case of I2S become the new standard. Ugh. Until that could every happen, I wish some manufacturer steering committee would have all manufacturers adopt a “standard pin out” for I2S so that stuff works together.

  7. I am usually happy in my blissful standards ignorance, but Paul’s post made me ponder what happened to TOSLINK. With other interface standards like USB or HDMI, it seems like there is a new “improved” iteration of the standard every few years. Why was there never a TOSLINK 2.0? Continuing the thought, why do we not see more trickle down of Pro Audio standards to the High End Audio market (Lightpipe, MADI, …). Is this this all the case of High End Audio manufactures not wanting/willing to adopt and interoperability standard?

  8. Rob watts of Chord electronics has been using galvanic isolation for a long time with his DAC designs.
    I use his Chord Qutest and have never had a problem. I use both coaxial and optical connected to external equipment. I have had that DAC for nearly 5 years now. It is a beauty.

    1. Glad to hear that you have a ‘Qutest’ Nick because I’ve
      been wondering about that little DAC for quite a while.
      What power supply do you use for it?
      Does it run off an internal battery?


  9. Sound doesn’t travel thru light…!
    Can you HEAR the sun…?

    I only use Toslink from my PC to SGCD. Just for concert videos so the limitations in ultra hi-res should not be a factor. Plus it is a longer run (in another room – fan noise!) and hopefully optical eliminates some of the PC noise nasties.
    The toslink ends are designed similar to USB.
    Push, rotate 90 degrees, Push, rotate 90 degrees, Push, rotate 90 degrees, Push, rotate 90 degrees only to realize it was aligned correctly the first time.
    Just ONCE I want to see a movie accurately portray the villain hacker make THREE attempts to get the thumb drive into the computer – like the REST of us do.

  10. Cheap TOSLINK can be made to work adequately … I currently use a very low cost set of active speakers, driven, only, over the optical by a DVD player. Using the throwaway plastic cable that came in the box with the speakers. First time I used a data link, so it was interesting experimenting – turns out that it’s very important to physically stabilise the cable, especially at the ends; optimising the precise dressing of the cable pays dividends.

    The cable was now good enough to point out that the status of the player was the next bottleneck. CD not mounted for minimum vibration, and the electronics not conditioned enough, is obvious – but get everything working to a good standard and then the setup delivers. Accurate, detailed, convincing reproduction … for very little money, 😉 .

  11. Thirty years ago, when I had my Audio Alchemy DAC, I listened to it both
    COAX & TOSLINK…couldn’t hear any significant difference & so I went
    with the TOSLINK, knowing that it would allow for electrical isolation.

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