Octave Jubilee Class A Mono Amplifier

The Jubilee Class A Mono is the top of the Octave range — Andreas Hofmann's answer to the question of what a Class A tube monoblock can be when power output is not the thing that gets sacrificed. It delivers 160 watts in pure Class A operation, and switches to 280 watts in a Class A/AB High Power mode when the loudspeaker asks for more. That is Class A power at a level most Class A designs never reach, in a chassis that stands 640 mm tall and weighs 53.5 kg.

Six matched KT 120 output tubes run per amplifier, driven by two 12AU7 and one 12BH7 — with autobias presets that also accommodate KT 150 and KT 170 tubes, so the amplifier can be revoiced by tube choice without a technician or a meter. Frequency response runs 15 Hz to 80 kHz, distortion measures 0.1% at 10 watts into 4 ohms, and signal-to-noise sits at 103 dB referred to maximum power in Class A low-power mode, on both the balanced and single-ended inputs.

What Hofmann designs toward is described plainly enough: ultrawide bandwidth with no ringing, and stability across every loudspeaker and cable combination. The Jubilee Class A holds a linear relationship between harmonics and distortion regardless of what the loudspeaker does to it — which is the engineering statement behind the listening impression, and the reason the amplifier's character does not change when the load gets difficult. Every transformer is wound in-house at Karlsbad, as it has been since 1968.

Within the Jubilee line the choice is genuinely about character rather than rank: the Mono Ultimate is the push-pull statement at 440 watts, the 300 B is the single-ended triode, and the Class A Mono is the one that holds pure Class A operation at real power. All three are worth hearing against each other on the same loudspeakers — walk in during business hours to hear the Octave Room in Scottsdale, or book ahead if you want a specific Jubilee configuration warmed up against your own recordings.