LUXMAN MB8A
¥ 31,000 (1 unit, no vacuum tube, sold in 1959)
¥ 37,000 (1 unit, released in 1959)
¥ 43,400 (1 unit, around 1964)
Commentary
A high-output monaural power amplifier announced as a top-of-the-line model.
The new OY36-8K was used for the output transformer.
This transformer uses a directional cold rolled core and is designed to have sufficient inductance so that it is relatively small but has low distortion at all output.
In addition, a special winding method is used to balance the secondary winding, which is utilized to apply NFB to the cathode of the power tube, resulting in a double negative feedback system of 28 dB in total.
In addition, the crossover NFB is also used in a double loop to achieve a low-distortion output over the entire bandwidth.
A push-pull circuit using 6GB8 is adopted for the circuit system.
Among four low-mu triode sections with two 12AU7s, one is a pre-amplifier section, two are cascode circuits, and the last one is a PK division phase inversion stage.
The power tube is class B operation. The optimum balance can be adjusted with VR1, and the push-pull DC balance can be adjusted with VR2.
Power supply circuits for preamplifiers and tuners are installed.
It is equipped with a volume and can be used independently of the main amplifier.
Model Rating
| Type | Tube type monaural power amplifier |
| Input voltage | 0.9V |
| Output | 70W (20 Hz ~ 20 kHz) |
| Output impedance | 4 Ω, 6 Ω, 8 Ω, 10 Ω, 16 Ω |
| Signal-to-noise ratio | 90 dB or more |
| Frequency characteristic | 12 Hz to 25 kHz -1dB |
| Negative feedback | 28dB |
| Distortion factor | 1%(20Hz) 0.4% (30 Hz to 10 kHz) 1% (17 kHz, maximum) |
| Vacuum tube used | 12AU7x2 6GB8x2 5AR4x2 |
| Power supply for preamp and tuner | DC310V50mA For Heater : 6.3V3ACT/12V1A |
| Pwer | 90 ~ 110 VAC, 50Hz/60Hz |
| Power consumption | Approximately 110W (No Signal) Approximately 200W (at maximum output) |
| External dimensions | Width 445x Height 246x Depth 198 mm |
| Weight | 16.7kg |