V 70 CLASS A

Bias Control is Octave's answer to the usual Class A tradeoff between low distortion and limited power. The circuit shifts the amplifier's operating point dynamically, roughly doubling the output of a conventional Class A design to 2x50W RMS at 4 ohms, with peaks up to 70W when the Super Black Box power supply is connected.

The amplifier runs four KT88-S4A-Carbon output tubes as standard, with KT120 TS tubes available for the Power High setting; less powerful KT88 or 6550 types run in Power Low. An auto-bias circuit adjusts to whichever tube is installed, so there's no manual bias adjustment required, though the BIAS LEDs still let you confirm all four output tubes are working correctly.

A balanced XLR input comes standard alongside five RCA inputs, one set up as a bypass and one available as a phono input with the optional MC or MM board. A regulated preamp output supports direct connection to a subwoofer, and the Home Theater Bypass circuit lets the amp sit in a multichannel system without disrupting the front channels.