There’s A Fiber Optic Connection Built Into Every Mac

[ This article was first published in the April, 2010, issue of
Larry’s Final Cut Studio Newsletter. Click here to subscribe. ]

Did you know there’s a fiber optic connnection built into every Mac?

Nope, I didn’t either. I didn’t discover it until we started our technical preparation for NAB this year.. It’s called TOSlink.

(Image courtesy of Hustvedt.)

According to Wikipedia, “TOSLINK or Optical Cable is a standardized optical fiber connection system. Its most common use is in consumer audio equipment (via a “digital optical” socket), where it carries a digital audio stream between components such as MiniDisc and CD players and DAT recorders.”

TOSlink was originally created by Toshiba to connect their CD players. Basically, it transmits digital signals between devices using fiber optic cables. And, as you can see below, it uses a square plug to connect to the gear.

NOTE: S/PDIF optical and TOSlink are two words that mean the same thing.

I learned about this in talking with Wayne La Farr, product specialist for Aphex. We were setting up the studio gear for our NAB coverage and I was planning on outputting the final signal as analog from the 320D Compellor into the streaming server. Wayne suggested I use a digital signal.

However, as I was streaming from an Intel iMac, I didn’t think I had S/PDIF optical connections. At this point, Wayne told me that I was wrong – they were just hidden.

Because we would be running cables in a high traffic area, we decided to use AES copper cable — it looks like standard XLR mic cable, but manufactured to higher standards — from the audio rack to the streaming server. This was a distance of about 20 feet. Then, we would convert the AES signals to TOSlink and connect them into the back of the iMac.

The conversion is done using the Hosa S/PDIF Optical to AES/EBU Digital Audio Interface. That converts the digital signals carried over copper wire to digital signals carried over fibre.

We added a short length of fiber optic cable to go from the Hosa to the back of the Mac. This created a fully-digital signal path from final signal processing in the Compellor to broadcast — IF we could get it into the Mac.

And here is where the magic occurred.

The Microphone In and Headset Out ports of ALL Macs support BOTH optical and copper signals (digital and analog). If you plug in standard audio plugs, the ports become analog. However, there’s a special TOSlink adapter that turns a standard 1/8-inch miniplug into a hollow tube that light shines through. Plug this into ANY Mac and the port switches from analog to digital.

Poof! Audio quality into your Mac as high as 24-bit, 96 kHz!

Very cool.

The only problem I had was that the system worked great during our initial setup in the office. But once we got to NAB, it kept dropping the signal. We would start recording and in less than 45 seconds, the signal would drop out.

Whether this was due to a bad power supply, bad mini-plug converter, or bad Hosa unit, we did not have the time to diagnose. We instantly dropped back into analog so that we wouldn’t miss deadlines.

However, this technology has the potential to be very cool and worth exploring. If I have a similar opportunity, I’ll buy the gear with a money-back guarantee a couple weeks before I need it to be sure everything is working properly.

Because when it was working, it sounded GREAT! I just wish we could have figured out how to get it to work more reliably.