The Mullard ECC81 was designed for RF use and is of medium impedance. It was used as a frequency changer in five station television sets. The ECC81 also makes an excellent phase splitter in modern audio applications too.
Indeed, almost all guitar amplfiers ever made use the ECC81 as the phase splitter - they make a Fender sound, well....... wonderful. Many players swear by the use of the ECC81 in the Marshall driver stage which gives a sumptuous bright and smooth tone.
Construction comprises of a glass envelope approximately 20 mm in diameter and excluding B9A button base pins the height is approximately 47 mm.
Used also in some stunning classic valve audio amplifiers – the Michaelson-Austin TVA-1 for one, some Leak for another as well as an ubiquitous component in nearly every guitar amplifier ever made, here is a list of some more recent exotica where the ECC81 does duty:-
APEX 460 TUBE MICROPHONE ART Pro VLA Compressor Art Pro VLA II Atma-Spere Preamplifier MP-1 Mk. III Audio Experience Balanced A2 Audio Experience BALANCED A2 SE preamp Berning ZH270 amp Berning Quadrature Z amp CJ PV10A Earmax Anniversary Earmax Silver Edition Ensemble Evocco Integrated amp 1998 Fender Bandmaster 1967 Fender 100 Watt Twin Reverb 1982 Fender Concert (II) 1983 Fender reverb tube Fender Super Reverb - Super Reverb Phase Inverter position V6 JC Morrison custom phono Jolida 302 Juicy Music Tercel II phono pre-amp Kora integrated amp Lector CDP 0.6T Manley Reference Cardioid mic Manley Snapper Marshall Electronics MXLV69 Mogami Edition Studio Microphone MXL V69 large diaphragm Tube Condenser Microphone Presonus ADL 600 mic pre Two Rock Victoria Regal VTL Tiny Triode amp WAVAC 805 SE amp