The MB81 SE are valve power monoblocks in a pure, fully triode single-ended configuration, built around the powerful 1950s Russian GU81 transmitting valve. They deliver 100 W per channel with an easy, relaxing and effortless sound — the result of the output valve working at just half of its capability (350 W plate dissipation), which also translates into exceptional longevity.
The pure-triode input stage uses two 6SN7 valves, and the driver stage a KT150 (or KT120) valve in a choke-loaded arrangement. The design was refined over hundreds of hours of listening and several iterations to fully exploit the potential of the GU81. The output transformers are made using the proprietary LDT (Low Distortion Tertiary) technology.
Each monoblock is fully hand-assembled, point-to-point, with no printed circuit boards, with an „easy bias” meter that makes it easy to monitor valve operation. Gold-plated sockets, an included valve cage and optional Mundorf silver/gold capacitors complete this uncompromising design.
| Output power | 100 W (8 Ω, at 1 kHz) |
| Output valves | 2× GU81 |
| Driver valves | 2× 6SN7 + 1× KT150 (or KT120) |
| Operating mode | pure Class A, single-ended triode |
| THD distortion | 0.2% (8 W) / 0.5% (50 W) / 1% (96 W) |
| Sensitivity | 400 mV (0 dB FB) / 800 mV / 1.2 V |
| Signal-to-noise ratio | −90 dB |
| Damping factor | 5 |
| Frequency response | 20 Hz – 20 kHz (−1 dB at 8 W) |
| Input impedance | 47 kΩ |
| Speaker impedance | 3 – 16 Ω (4 and 8 Ω taps) |
| Power supply | 235 / 117 V; 450 W typical |
| Dimensions (W × D × H) | 450 × 660 × 385 mm (400 mm with cage) |
| Weight | 50 kg (each monoblock) |
Single-ended valve power monoblocks on GU81 valves — 100 W of pure Class A, fully triode, hand-wired with an easy-bias meter. Effortless, relaxed sound with no compromise.
