For the electronics enthusiast a tube audio amplifier makes ... using a double triode and a power pentode for each channel. It follows a so-called ultra-linear circuit, with a tap on the output ...

It’s a conventional tube amplifier circuit in which the triode is a preamplifier for the pentode power output stage. The pentode is running in class A mode, and the high impedance of its output ...

This circuit layout produced low distortion, prompting Quad to promote the 303 as “the world’s first low-distortion transistor amplifier”. At the rear of the Quad 303 power amp are the ...