Monday, May 16, 2016

Can Graphene Semiconductors Make Future Solid State Audio Power Amps Sound Like Vacuum Tube Amps?

Given that electrons can travel more than 100 times faster in graphene than in copper, will the upcoming graphene based semiconductors make solid state amps sound like vacuum tube amps? 

By: Ringo Bones 

Though they’ve been identified as far back as 1947 as being 207 times stronger than steel and make electrons travel 100 times faster through them than through copper wires, the carbon allotrope graphene was only manufactured / synthesized in significant amounts back in the 1970s by Manchester University physicists Prof. Andrei Geim and Konstantin Novoselov which made them the recipient of the 2010 Nobel Physics Prize. But more recently, various methods to manufacture graphene in higher volumes and far lower costs than before have recently made them economically viable enough for semiconductor applications. Given faster electron flow / electron mobility and high tensile strength, could upcoming graphene semiconductors someday make solid state hi-fi amplifiers sound like their famed vacuum tube counterparts? 

During the 1990s many research articles were written about why hi-fi solid state power amplifiers sound different from their thermionic vacuum tube counterparts. But during the latter half of the 1990s, solid state integrated amplifiers that used “high electron mobility” semiconductors – i.e. solid state devices that used indium antimonide that are "blocked out" to protect the secret of their designs whose electron flow is up to 50 times that of copper wire and or power transistors enclosed in nonmagnetic packaging like TO-3 packaged 2N3055 NPN transistors in brass as opposed to the bog standard magnetic stainless steel. Even though these amps tend to be overpriced – average price between 3,000 to 5,000 US dollars each were their equivalent circuit counterparts using bog standard output devices tent to sell on average one-tenth of their price. Many audio engineers and hi-fi enthusiasts have wondered whether the difference in sound / timbre of solid state power amps and vacuum tube power amps is largely due to the speed of electrons travel through their output devices. 

Electrons and electromagnetic waves propagate in vacuum at a maximum speed of 299, 792, 458 meters per second – usually rounded to 3-million meters per second or more famously known as 186,000 miles per second or 670-million miles per hour. A 12-gauge copper wire carrying a 10-ampere DC current, the speed of the electrons traveling through it is about 80 centimeters per hour – or about 0.0002 meters per second. A current traveling through a silicon-based semiconductor is about the same. While a velocity of an electron by the time it reaches the anode after being accelerated by the anode’s field is truly mind boggling by comparison. For example a vacuum tube with a fairly typical anode voltage of 450-volt DC, the electrons will hit the anode at approximately 12-million meters per second or 28 million miles per hour.  

Remember those “overpriced” integrated amplifiers that use exotic high electron mobility solid state devices that sound like vacuum tube power amps? The average electron mobility rating of the active output devices that these amp use are 50 times that of typical silicon based output devices. Is electron mobility / electron speed the secret to better subjective sound quality? Well, electron flow in a typical indium antimonide semiconductor is around 0.01 meters per second and on graphene based semiconductors is 0.02 meters per second – quite a lot faster than a silicon semiconductor’s 0.0002 meters per second. Will high electron mobility spell improved subjective sound quality for upcoming graphene based solid state high fidelity audio amplifiers?