KT88 is a glass-envelope beam power tetrode. It is intended for audio frequency power amplification service. High plate dissipation rating, close manufacturing specification tolerances and thorough processing provides improved reliability and superior sonic performance.KT88 is manufactured in Russia, and is designed to be a direct replacement for any KT88, KT90, KT99 or 6550.The new KT88 features greatly enhanced sonic performance: Increased peak cathode emission from new cathode materials; Stable operation from extended processing and aging; Gold-plated grid; New tri-plated grid; New tri-plate anode; Single-piece beam forming electrode; Precise grid/screen alignment; Improved vacuum processing; comprehensive static and audio amplifier testing before and after aging.