voodish logo
tweet rss book of faces Linked In

Digital Music history

The digital compact disc is the most successful consumer electronics entertainment medium in history. It has been available for longer than Edison’s cylinders, Philips’ cassettes, Pioneer’s laserdiscs or JVC and Sony’s videotape formats.

The LP record has a longer history, but there is more music available on CD than there ever was on LP, and a greater number of CDs in circulation. Indeed, the technology is older than most people think. This year marks the 80th anniversary of the invention of digital music.

There is some debate as to when the compact disc was invented because the idea of using an optical disc was first proposed by Dutch physicist Klass Compaan in 1969.

Mitsubishi, Hitachi and Sony all showed digital audio disc players at the 1977 Tokyo Audio Fair, two years before Philips first demonstrated its digital audio player and four years before the Digital Audio Standards committee formally adopted a joint Philips/Sony proposal for the system we use today.

If you look on the back of a CD player with a digital output socket, you may find the letters “SPDIF” alongside it. These stand for Sony/Philips Digital Interface Format.

The real credit for the compact disc format belongs to Swedish physicist Harry Nyquist. In 1928, he realised it would be possible to represent an analog audio signal with a stream of 1s and 0s, and also worked out how often you would need to sample the audio signal in order to turn the digital data stream back into an audio signal without any loss of quality. What’s now known as the Nyquist Theorem states that for accurate digital coding and decoding, the sampling frequency must be twice that of the highest audio signal you need to reproduce.

The CD format’s sampling frequency is 44.1kHz. This gives a theoretical maximum playback frequency of 22.05kHz, so it may come as a surprise to learn that, until now, no CD player has ever been able to accurately reproduce a 22.05kHz signal.

Another surprise is that although CD players are supposed to be reproducing music with 16-bit accuracy, very few do. In fact, the very first Philips CD player didn’t even have a 16-bit digital-to-analog converter (DAC): it was only a 14-bit chip. And while Sony’s first CD player did contain a 16-bit chip, its accuracy was only about the same as Philips’ DAC. In all cases, performance was being limited by physical constraints involved in the fabrication of integrated circuits.

Yamaha was the first manufacturer to realise that the easiest way to improve the accuracy of the digital-to-analog conversion process was to increase the number of “bits” the DAC could decode. It developed the world’s first 18-bit DAC. The two “extra” bits served only to improve the accuracy of the other 16.

Gryphon, a small Danish manufacturer, realised it could play the same trick with the CD’s sampling frequency. Its CDP1 CD player was the first to feature a sampling frequency of 88.2kHz. This meant the CDP1 read each of the 44,100 samples stored on a CD twice. This didn’t extend the frequency response, but it reduced the number of errors when reading, which improved the accuracy of the recovery process.

Since then, manufacturers have slowly been increasing the sampling rates of their CD players and employing ever-improved methods of digital-to-analog conversion in their efforts to improve the accuracy of the signal recovery from CD.

Gryphon’s Mikado Signature CD player, released last week, is now the world’s most advanced. It uses four 32-bit DACs (two per channel) and samples at 192kHz.

The company’s founder, Flemming Rasmussen, says the increased resolution that results not only reveals musical subtleties and nuances that have previously been inaudible, but also drops the noise floor below that of the original recording.

The circuitry in the Signature is fully balanced through both the analog and digital domains, with separate regulated power supplies for each. TheCD transport is a re-clocked Philips CD-Pro 2.

Mindful of the fact that digital technologies will probably continue to improve, the digital audio sections are contained on modular and removable boards. Rasmussen says this means owners will be able to upgrade the boards rather than having to replace the player.

Sennheiser says the sound is demonstrably superior to that of conventional wireless earphones.

This improvement is partly due to the quality of the drivers used in the earphones but mostly because of Kleer’s digital radio-frequency transmission technology.

Other wireless systems use analog radio-frequency techniques that require the music to be compressed before it’s transmitted but Kleer’s digital system handles uncompressed music.

Kleer has started licensing its technology to makers of MP3 players so that in the near future, MXW1 owners will be able to buy players with transmitters, so there will be no need to carry a separate transmitter.

Related Articles

Comments RSS Feed

No Comments Yet

You can be the first to comment!

Leave a comment