AUDIO VALVES: EL84 6BQ5 CV2975 6P15 N709 OUTPUT PENTODE

The EL84 output pentode was introduced by Mullard in 1954. To demonstrate its use and quality the Mullard applications lab produced an amplifier design - the now classic 5-10 high quality audio amplifier.   When used as a pair in an ultra-linear push-pull configuration with 43% distributed loading the output could reach 10 W with 0.9 % total harmonic distortion. 

 With ultra-linear operation the screen grids were connected to taps in the in the output transformer primary winding. The valve operating conditions so produced were intermediate between a triode and a pentode. The operation of the distributed loading was to introduce negative feedback directly within the output stage. The EL84 found use in many classic valve guitar amplifiers, classic and current  valve hifi amplifiers including: -

Bad Cat
Black Cat 2003 
Blackheart BH5H
Consonance Cyber 20 headphone amp
Dr. Z Carmen Ghia 2005, 2006
Dynatron 15
Elk Sonic 102
Epiphone Valve Junior
Fender Vibrolux
Gibson GA-5 Skylark 1966
Lafayette LA-224A
Leak ST20
Leak TL12+
LEBEN CS-300XS
Lexicon Signature 284
Lowther LL10
Manley RM10
Marshall EL84 amp 1974
Matchless C-30
Ming Da MC 84C07 headphone amp
Mullard 5-10
 Reinhardt 18W Marshall clone 
 Shindo Montille,  RM10
Sterns 5-10 
Triode TRV-84HD, 65amps
VOX AC10, AC20, AC30, 
65amps Lil Elvis combo