Toslink Digital Audio & The Lifatec Silflex Optical Cable

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Lifatec Silflex glass optical cable

The transmission of digital audio signals has evolved and improved over the years, resulting in several standard formats for both consumers and professionals. When Sony and Phillips were creating the Red Book CD standard they also included an option for digital audio to be transported between components. While the S/PDIF (Sony Philips Digital Interface) standard was created using coaxial cables (electrical voltages over copper) with RCA connectors, Toshiba proposed a novel solution. Optical light emitted from a red LED was used to create  binary pulses that distinguished digital 1’s and 0’s.

Toslink, or more accurately EIAJ optical, is the standard for using collimated light in the transmission of digital audio. Optical fibers are used as circular dielectric wave-guides that transport optical energy and information.

Early forms of this technology suffered from jitter (phase noise from inaccurate clocking) and data errors or drop outs from bandwidth-limited optical cables. Using digital audio chips with improved clocking and digital inputs aimed at reducing jitter is a good start, but to ensure those binary pulses of light reach your downstream component (i.e. DAC) without error requires a cable capable of delivering the full bandwidth spec of the Toslink standard.

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                                       Lifatec custom machined Toslink connectors

While I use AES digital connections in much of my professional audio work, Toslink optical interfaces are often the only available digital input/output for many consumer devices. Apple TV, Playstation, Roku, and most flat screen TV’s only provide optical outputs. With mixed results from Toslink cables made of plastic, I began researching Toslink cables made from glass fiber strands.

After some digging, I stumbled upon LiFaTeC® GmbH, and their North American partner Lifatec USA. The American firm specializes in using optical borosilicate fibers in lighting and sensing products for the medical market, and since 2000 Lifatec USA has been manufacturing glass Toslink cables in Elbridge New York – named the Silflex glass cables.

To achieve a bandwidth beyond the Toslink spec, Lifatec uses 470 glass fiber optic strands in the Silflex glass cables. These glass fibers are custom built specifically for audio data applications. Keeping these strands in place is a smooth outer jacket that encases the fine fibers called Optisilk. Before terminating the glass strands, the ends are bonded together and polished to a 1 micron optical finish (including the connector ferrule). Then, a custom machined Toslink connector that is both robust and lightweight ensures a tight connection without light leakage.

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Lifatec glass optical cable with mini Toslink connectors on one end (Apple Laptops)

For my testing, a 10 ft Lifatec Silflex cable was used to link digital audio sources with digital to analog converters. I used my Playstation and a Blu-Ray player’s optical output to send digital audio data to several DACs for testing. All of my DACs quickly locked to the incoming signals without a hiccup. Sonically, the sound of the Silflex glass cable was clear and transparent, imparting no sound of it’s own. The most important difference I found, when compared to other optical cables, was the tight fitting connector in the Lifatec cables. I used one optical cable where the manufacturer thought it was a good idea to machine a Toslink connector with an unnecessary amount of bulk, which added weight. This inferior connector (from a popular audiophile manufacturer) would easily fall out of the female Toslink socket, not so with the Lifatec cable.

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The custom machined Lifatec Toslink connector is both lightweight and tight fitting

After spending some time with these cables in my system, it became clear that the Lifatec cable was a well engineered product for optical audio transmission. Fine borosilicate fibers and smooth outer sleeving allow the cable to flex and fit around components with ease. The finely polished ends ensure a strong optical signal, and the robust/lightweight connectors prevent any light leakage. It is rare to find such a well thought out cable with quality in every part of the build. It’s even less common to find these high-end custom designs at real world prices. Without hesitation, it is my pleasure to recommend the Lifatec Silflex cable for all your optical audio connections.

Happy Listening!

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Crane Song Avocet with Quantum DAC

QuantumDAC

David Hill of Crane Song LTD builds some genius pro audio equipment. His mic pre amps and compressor designs have always held a special place in my sonic memory. I’ve been lucky enough to use his gear in broadcast studios and through my own personal music recordings.

The Crane Song Avocet is a Class A monitor controller with a built-in DAC (Digital-to-Analog Converter). Having undergone 5 iterations, the current  Quantum DAC boasts impressive jitter specs and uses a proprietary reconstruction filter for accurate time domain response. Operating asynchronously with a 32 bit architecture, the reference clock is less than 1pS and all digital inputs are up-sampled to 211Khz.

Upgrade Note: If you are sending in your Avocet for the Quantum DAC upgrade, you will receive an optical input that replaces the original dual wire AES input. Cool, now you have AES, S/PDIF, and Optical.

The design is utilitarian and solid- sporting a modern industrial build with primary colored buttons and center volume knob. This might sound strange, but it always reminded me of Jacque Tati and his modernist take in films like Playtime (go to 23 sec). Monsieur Hulot would surely get lost in the maze of colored square buttons ;). The Avocet proves smart modern design can improve the future for all…err, yeah that is… for Audio Engineers!

AvocetIIA

Talking with David Hill at AES last year revealed his excitement about this new Quantum DAC design. In particular, David felt that the combination of filters being analog and some digital help provide a more realistic impact of sound. His words, if I remember correctly were, “a snare hit now sounds more like the real snare.” Now that I had Mr. Hill’s new Quantum DAC in hand, it was time to test it out.

To listen, I brought the upgraded Avocet down to a studio with Lipinski speakers and amps. There, we also had a previous generation Avocet to listen to and compare. A good hour of warm up was given, and a couple more listening to various digital audio sources from the SADiE DAW. Quantum entanglement aside, we began listening to this latest generation DAC design from Crane Song.

Using some familiar music tracks, we fed the Quantum DAC via AES/EBU, then out to the Lipinski speaker system with amps. It certainly sounded good right off the bat, but only after spending a little time did all the new sonic upgrades become clear. Switching to the previous generation Avocet DAC proved that this new design provided a more robust or dimensional envelopment to sounds. David was right about the snare sound. Even more, the guttural impact of kick drum was solid and more 3D. Instruments achieved a more realistic timbre and acoustic space with this Quantum DAC upgrade. While the previous generation DAC is no slouch, this new design allows a more fleshed out roundness to the instruments in the stereo image. remoteThe user-interface offers simple and functional controls that allow you to smartly and intuitively work. With the precise relay based volume control (with offsets for level matching) and brilliant class A output stage, the 5th generation Quantum DAC furthers audio resolution while maintaining full control of your audio sources. The Crane Song Avocet maintains its place as the hidden gem of my audio experiences. My highest recommendation.

-Happy Listening!

The Norse Gods Awake – The Hegel HD20 DAC

Hegel HD20 DAC with 2 Coaxial S/PDIF inputs, 1 USB, and 1 Optical input

I am currently listening/evaluating the Hegel HD20 DAC. This DAC from Norway provides a preamp for directly driving power amps, or line level out to a separate input stage. Note: A specially designed coaxial input  claims to corrects impedance issues normally found on digital RCA connectors. Stay tuned for a full review.

Hegel Music Systems

On my last day at T.H.E. Show Newport I walked toward the light.  Literally, the only audio exhibitor who had the beautiful California sun filling the room was Hegel Music Systems of Norway. Hegel electronics paired with Amphion speakers produced a clean modern aesthetic that made me feel welcome. I soon learned that the technology behind Hegel amplifiers was truly unique.

Eileen of Hegel really took her time to demonstrate and explain the technologies contained within their product line. The demonstration focused around using a Hegel CD player, 2 different DACs (digital-to-analog converters), and the H70 integrated amp to power the Amphion speakers. The idea was for a listener to become familiar with a CD music track (converted by the CD player’s onboard DAC) then hear the same track converted through the two different outboard DACs made by Hegel (the HD11 and the HD20). The sonic benefits in jitter reduction and power supply design were readily noticeable. Well Done.

Hegel H70 Integrated Amplifier

The amplifier technology from Hegel was impressive in that it is able to maintain a high damping factor *(greater than 1000) while using a class A/B design. I was told that by eliminating feedback loops associated with other amp designs, the Hegel amps are able to have less distortion. They use what they call a “feed forward” design. I can certainly attest that this little H70 integrated amp (70 watts a channel into 8ohms) was truly a beast! I can imagine that speakers with decent sensitivity will love the H70’s control and articulation. Most importantly though was the fact that the Hegel amplification seemed to get out-of-the-way. It amplified music effortlessly and seemed to sonically disapear. The H70 also provides analog rca inputs and even a balanced pair of inputs. Hegel even gets you set up to receive digital inputs like coaxial/spdif, optical, and even a USB input for computer audio.

While I have not had a chance to fully review these amps with speaker I am familiar with, I have a good sense of the sonic picture since the Amphion speakers were used  – A Finnish company that has ties to Genelec from the professional speaker world.

Below please find some pictures of the Hegel designs:

Hegel H20 amplifier

Hegel H100 integrated amp

*See my post on Green Amplifier Technology

Hegel amps are GREENER *It should also be noted that the Hegel Class A/B amplifier designs use 60-70% less power than traditional Class A/B amplifiers. This is due to Hegel using a lower bias current on the amp’s transistors.

Here is a video about the Hegel design.