From the perspective of optimum sound quality, is copper – as opposed to the de rigueur aluminum – the best material for making audiophile quality compact discs?
By: Ringo Bones
Since its introduction in 1983, it seems that aluminum – as in aluminum alloy containing 2 percent iron – has been the de rigueur material in manufacturing CD albums destined to record stores. Gold plated aluminum – its way distant second place competition – were more often than not used in manufacturing the higher grade sound quality / audiophile versions of its bog-standard aluminum counterparts. But what if there is another compact disc manufacturing material capable of much better sound quality – like offering much reduced jitter. Would the world’s leading CD manufacturers jump upon it?
In an interview by The Absolute Sound magazine back in 1996 - as in the July/August 1996 Issue 107 of The Absolute Sound magazine - audio-guru and head of Epiphany Recordings, Jeremy R. Kipnis, has experimented in using copper and even brass in making test CD pressings of exceptional sound quality in comparison to their bog-standard aluminum counterparts. According to Kipnis, brass CDs became a part of the continuing evolution of his own ideas about optical recording and playback media.
As everyone knows, aluminum reflects back equally all frequencies of light, which is why you get that pretty rainbow. CD is an optical carrier and jitter as a destructive entity can be modulated optically, just as it can be electronically. In the case of a CD, the more red-light that we can present to the CD player’s optics – and less of the other frequencies – the cleaner will be the resulting signal. According to the results of his experiments on this Jeremy R. Kipnis says that brass offers better results than aluminum while copper is even better. Gold offered good results but Kipnis says “I don’t think gold sounds nearly as transparent as copper”. So after 18 years of proving that copper sounds better than both aluminum and gold, why is it that not a single audiophile grade CD pressing is manufactured from copper?
Around 1997, the hi-fi / audio world shifted its attention on making recordable and re-recordable CDs for domestic use – the Orange Book spec consumer grade recordable CDs - an affordable reality. Even though it has been available since the late 1980s, recordable CD systems were about as expensive as an entry-level Ferrari supercar. CD manufacturers concentrated their energies on making consumer friendly – price-wise that is – write once CD-Rs using pthalo-cyanine dye technology CD-RWs using silver, indium, antimony and tellurium alloyed recording layer. Jeremy R. Kipnis’ idea of a copper CD seems to have been chucked into the dustbin of history as the year 2000 approaches.
Rifling through my CD collection, non-aluminum made CDs seems to be a very, very tiny minority when it comes to manufactured CD pressings. Given that via transmitted light aluminum can act like typical sunglasses filtering the light that tries to pass trough it and gold plated CDs are green via transmitted light, while copper CDs are purple when seen via transmitted light. Using this test it seems that I had only one copper-made CD pressing in my collection. It’s the album Shotgun Wedding by Lydia Lunch and Rowland S. Howard and it was released back in 1991! Unfortunately, this CD sounded no better or worse than its aluminum counterpart - copper CD pressings, anyone?