Tuesday, July 30, 2013

Will There Be A 12AY7 / 6072 Vacuum Tube Shortage?

Given that it is currently not manufactured by Russian, Eastern European and Mainland Chinese vacuum tube manufacturers, will the hi-fi world soon be facing a 12AY7 / 6072 vacuum tube shortage? 

By: Ringo Bones 

Even though the 12AY7 / 6072 vacuum tube is virtually similar to the double triode 12AX7 / ECC83 / 7025 vacuum tube, it is quite a mystery why the worlds currently existing vacuum tube manufacturers haven’t started making the 12AY7 / 6072 small signal vacuum tube anymore which is quite a shame given that it offers a tone that is more often than not never found in a current manufactured 12AX7 or ECC83 vacuum tube. 

The 12AY7 vacuum tube is a miniature dual triode vacuum tube with a 12.6-Volt / 6.3-Volt series/parallel heater, a B9A base. This tube is virtually similar to the 12AX7 / ECC83 and has the same heaters and pin-out configuration. It was probably developed by the same RCA electronic engineering team that developed the 12AX7 back in 1946 in Harrison, New Jersey. Though the 12AY7 tube was released commercially back in December 7, 1948. 

It was intended as a low noise small signal preamplifier tube for audio use and as such it is excellent. Its characteristics are just about for preamplifier applications where a gain of around 30 – half that of a typical 12AX7 preamp tube application – is typical for one stage of a 12AY7 tube and with a typically low output impedance. 

Microphony on a good 12AY7 / 6072 tube is just about nonexistent, noise is low but a 6DJ8 / ECC88 / 6922 tube will win in the end due to its “brute force” transconductance or gm. It would be sacrilege to use a 12AY7 tube as a driver tube because there are tubes which are better at being forceful. When used as intended though, the 12AY7 / 6072 tube has a rich, smooth and open sound quality which is very hard to beat. 

The 6072 version is a Soviet era high reliability / ruggedized military version and in my opinion it wins over its commercial new old stock (NOS) cousins in the sound quality stakes by being slightly clearer and more coherent while the typical new old stock 12AY7 tube is slightly softer and more euphonic. While both 12AY7 and 6072 have virtually similar electrical characteristics in both AC and DC conditions.
The only problem with the 12AY7 and 6072 vacuum tubes is their price. Although not yet reached stratospheric levels, both are more expensive than the plain old 12AX7 / ECC83 vacuum tubes. Stock levels are still relatively high back in the 1990s to as of today, but unless current vacuum tube manufacturers restart producing the 12AY7 and 6072 vacuum tubes soon, there would soon be a 12AY7 / 6072 vacuum tube shortage that would make their current retail prices rise to stratospheric levels faster than a Soviet era supersonic capable strategic bomber. 

Even though the only sources of 12AY7 vacuum tubes are new old stock Sylvania types, the Soviet era 6072 vacuum tubes comes in boxes that show their age despite passing with flying colors in a small signal tube checker. Its as if most 6072 tubes currently available today dates back to when Leonid Brezhnev was still the head of the then Soviet Union. The only commercial amplifier manufacturers I know of currently using the 12AY7 tubes and 6072 tubes are Audio Note and World Audio Design in their 300B Amplifier. 


K8-LYN said...

The first time I read about a looming shortage of 12AY7 vacuum tubes was in an April 1995 issue of Hi-Fi World magazine. The rational being is that the only source of 12AY7 vacuum tubes were new old stock vacuum tube stashes. Today, a typical 12AY7 vacuum tube costs around 2 to 3 times that of a typical audio-grade 12AX7 vacuum tube - although I've just seen an advert of 12AY7 vacuum tubes being made by Electro-Harmonix. Are the Electro-Harmonix brand new as in produced in the 21st Century versions of the 12AY7 vacuum tubes?

Ringo said...

A brand new 12AY7 vacuum tube by Electro-Harmonix? But to my ears at least - Electro-Harmonix vacuum tubes are more suited for electric guitar tone euphony than for sober high fidelity neutrality and "virtual reality".