DAC, Apple TV, and Telly

Lounge Audio and Video

Last summer I finally acquired a 21st century telly, a Panasonic plasma TV. My old Hitachi 27″ was refusing to die but it couldn’t do modern audio and video tricks so I upgraded. That was just the beginning of this adventure which continued with image adjustment and routing of audio over to the hifi. This last trick was not hard but not obvious.

The key to having high quality digital audio in the living room is a gadget called a DAC. This beastie turns a stream of numbers into electrical waveforms of the sort that appeal to audio preamplifiers, power amplifiers, and loudspeakers. I am fortunate to have chosen these wisely 35 years ago so they are quite musical and still going strong. I just needed to turn the digits into electrical signals. The DAC connects to a preamp line input just like a tuner or tape recorder so that was the easy part. There are two good DACs (sound and value) out there, the Cambridge Audio DacMagic and the Peachtree DACit. I chose the DacMagic based on AudioAdvisor and Amazon reviews. It was the one with the buzz at the time.

DAC, Apple TV, and Telly
21 Century Audio and Video!

It was the pieces in the middle that were the hard bits. The telly didn’t have analog audio outputs I couldn’t do that trick. It did have a TOSlink optical output so that was the way to go. The DacMagic has 3 digital inputs, one USB 2.0 audio in and 2 SPDIF/TOSlink audio in. TOSlink was the common interface so I ordered a TOSlink optical cable for $15 and was in business. The results are stunning. The TV sound has depth, detail, and a sense of space not possible with the little built in speakers. The only setting needed was to set the TV digital audio output for stereo disabling the Dolby Digital hokey surround sound that I don’t like. The telly mixes everything down to a clean stereo PCM sample stream.

The DacMagic is clever. It can do CD (44 kHz) or DAT (48 kHZ) and 2-times up-sampled stereo in 16 bit or 24 bit word length as supplied by the digital source. It converts the input stream to 192 kHz 24 bit word pulse code modulation and converts that stream of numbers to analog audio voltage. All of this just happens with no fuss after a little negotiation and a little delay to buffer the sample stream. The DacMagic retimes the word stream for proper reconstruction, does some digital filtering magic, converts to analog, and does some analog filtering magic.

Cambridge Audio has nicely voiced the DacMagic to pander to my preferences for a natural midrange, deep controlled base, and a smooth high end that reproduces what I hear listening to live cymbals. This combination makes a good sound track shine and is mercilessly revealing of shoddy work.

I use a TiVO HD in place of a Cox Motorola cable box. The TiVO connects via HDMI to the telly. TiVO delivers digital video and digital audio to the telly by HDMI cable. The telly passes the digital audio to the DacMagic by TOSlink cable. TOSlink is a fiber optic connection. This means there are no ground loops. A ground loop occurs when two pieces of equipment are at different ground potentials. When a ground loop is present, it always presents as a hum. In bad cases, enough current can flow along the ground conductor to damage connectors and equipment. Using an optical connection absolutely prevents this. Finally, TV audio that is listenable!

The pleasant surprise is that the telly digitizes the analog audio from my Pioneer DVD player without doing violence to it. A well-recorded DVD sound track plays with clarity and a nice sense of space.

Apple TV works nicely to play iTunes rental movies and music and videos from my iTunes library. Apple gave me a nice housewarming present last July, the iTunes Festaval app. This free iPad program played video of the London iTunes Festival which runs during July. About 20 nights and 40 acts. Seasick Steve with Drummer Dan and John Paul Jones (think Led Zeppelin bassist) and friends sitting in stole the show. They showed some young punks that old men could still pick a mess of blues. The video and audio production was first rate and Steve was magic with his Diddley Bo and soulful beater guitars. A Fender Tweed (also a beater) was a big part of his overdrive sound.

The iTunes Festival App runs on iPad. Apple AirPlay gets the bit stream to the Apple TV by WIFI for playback. HDMI to the telly for both audio and video. Telly sends the audio word stream on to DacMagic for reconstruction. Man did it sound good. The audio engineers had guts to put down strong bass and a robust natural high end that showed off Dan’s cymbals. And John Paul Jones can pick with the best of them on bass guitar, guitar, and mandolin.