On the picture you can see the Matchless DC30 at the bottom left.
The preamp sections are based on a layout of two 12AX7's in Channel 1 and one EF86 in Channel 2. The twot 12AX7's in Channel 1 create a parallel-triode circuit with interactive bass and treble. The one EF86 in Channel 2 consists of a high-gain pentode coupled to a six-position tone switch. Outright benefits include quick dial-in of new tones and an easy return to the settings you learn to prefer. Also high treble cut control, master volume, with a bypass feature that offers flexible control of the power amp section. The power amp is fed by a 12AX7 phase inverter, which drives four EL84 power tubes. The rectifier circuit gives you the flexibility of using one 5AR4 for a quick attack or you can use two 5V4's for a smooth round response. Other professional features include an effects loop, half power-mode switch (a conservative 30 watts switching to 15 watts), output impedance selector (4, 8, 16 ohms) and a speaker phase-reverse switch.