The most versatile B9A twin-triode valve in history saw the commercial light of day during early 1948. Developed by R.C.A at their Harrison, New Jersey facility in the USA. At it's introduction, it was heralded as the first twin-triode device engineered for high gain, low noise applications. This versatility represented vast business and the giant Philip - Mullard conglomerate watched from the wings awaiting a slice of the action!!
Philips tasked it's famous R&D department to work with the goal to develop the best ECC83/12AX7 type made. Almost obsessive detail to control grid windings, electrode metallurgy quality control and enhancement of cathode emissive materials achieved during the 1950's resulted in the much feted Mullard ECC83.
The ECC83 high impedance amplifier triode was designed specifically for audio use and has a high amplification factor of 100. Mullard describe the ECC83 as a high mu double triode, having separate cathodes, primarily intended for use as a resistance-coupled amplifier or phase inverter. Physical dimensions for the ECC83 are as stated: - envelope of 21 mm diameter and of thin glass wall construction.
This valve type is extensively used in today’s designs of hi-fi audio amplifiers in very much the same way as they found use in the Mullard and other classic audio amplification designs of the 1950s and 1960s with the valve's two triode sections being used as second stage amplification and cathode coupled phase splitter - the phase splitter being required so that the push-pull output stage was driven correctly, the following list gives you a taste of the range of exotica old and new that uses the ECC83:-
Aestetix Rhea phono
Allen Sweet Spot 2008
Art Audio MPA Gold pre
Art Audio phono
Art Pro Audio MPA
ART MPA Gold 2 Channel Microphone Preamp
Audio Research linestage
Audio Thrills phono
Bad Cat 'Custom Shop' Cub II R 1 x 12 Combo Tube Amplifier