AUDIO VALVES: 12BH7 12BH7A CV5042 13D6 TWIN TRIODE

The 12BH7 double triode was first introduced in 1950 as a TV frame oscillator, verical deflection amplifier or output valve demonstrating a medium-mu characteristic curve.  However, it's pin compatibility with the ECC81 - 83 range of twin triodes along with it's higher anode disssipation and large rigid anode construction makes it eminently suitable for high grade audio usage.

There is much fokleore about the 12BH7 as opposed to the 12BH7A variants and the distinction between the two is simple with the 12A differing from it's younger brother ONLY by incorporating a controlled filament heater which was introduced to stop flash-burnout on series connected heater chains in 1950s designs of television receivers.  This difference imparts no discernable sonic improvements nor detractions and as a consequence I consider both variants to be interchangeable.

Today, these beautiful twin triodes are found in audio exotica such as: -

Ampeg SVT
Art Audio Carissa Signature amp
Art Audio Diavolo amp
Art Audio PX25 amp
Audio FSK amp
BLACKSTAR HT-5 
Blackstar HT5 2009
Bottlehead Crack with Speedball
Doshi Alaap preamp
Kendrick Solo 7
Kora Hermes DAC 
Luxman MA-88 amp
Manley
Manley Neo Classic 250 mono amps
Mapletree Audio Design Ear+ 
McIntosh
McIntosh MC30
Octave M90 mono amps 
Quicksilver Audio V4 mono amp
Quicksilver Triode amp
Ray Samuels
Requisite Audio preamp
Teletronix LA-2A Compressor/Limiter
Thor
Universal Audio LA2A
Valvet L1
Valvet L1 preamp
VTL MB450
Ampeg SVT
Vexo S40 amp