Introduced in late 1961, the ECL86 has the distinction of being one of the last combined single envelope audio triode and output pentodes to be introduced to market.
The ECL86 was designed for use in stereophonic amplifiers with it’s inherent high amplification factor allowing the signals from crystal and ceramic pick-ups to be amplified to speaker-driving level with the minimum of components. Mullard period advertising went on to laud the ECL86 in glowing terms: -
"The new Mullard triode pentode - the ECL86 - is designed specifically for audio applications and is particularly suitable for stereophonic amplifiers. The sensitivity of the valve is such that the output derived from low-sensitivity crystal and ceramic pick-ups is adequate to produce a useful output of 3W from the valve in an atypical single-valve circuit and to allow the use of negative feedback. Special care has been taken in the design of the ECL86 to keep hum modulation to a minimum, and a hum voltage of 4µV, referred to the triode grid, is attainable."