The JJ KT77 is an alternative to the more common EL34 tube.
The now rare KT77 tube was introduced by MO-Valve in the late 1950's and has been brought back by JJ. They use the same biasing so they are a great substitute for the EL34 in any tube amp. No circuit mods required.
Compared to the EL34, the KT77 has an extended but balanced frequency range with fatter bass and chimey highs. The mids are very smooth and when driven they're rich and complex. Great in Marshall applications and anywhere added harmonic complexity is desired. They breakup earlier than a 6L6 but have more headroom and less compression compared to the EL34.
Open Datasheet - KT77
