LUXMAN MA-88

Commentary

A bulb-tube monaural power amplifier designed as a new age bulb-tube power amplifier based on accumulated technology and know-how.

Golden Dragon KT-88 Super is used for the output tube.
The KT-88 Super is a beam tube that has been improved by changing the plate material of the KT-88, which has been most widely used in the world. It has better strain rate characteristics than the original KT-88.

The first stage uses 12BH7A, which has a large plate shape and good sound quality, and the driver stage uses 6CG7, which has low output impedance and excellent drive performance.

40-50W output is required to support modern speakers with low efficiency and large impedance fluctuations. Therefore, the MA-88 does not use a triode connection or UL connection as the output tube, and uses a pentode connection with minimal phase rotation without waste.
In addition, a dedicated current is used for the screen grid using a rectifier tube 6X4WA. The plate and the screen grid are separated to stabilize the operation standard, and the operating voltage is set to an ideal value to give consideration to the life of the vacuum tube.

The Williamson circuit is used for the circuit configuration. In this method, the reference is always clear because there is no capacitor at the amplification reference point. In addition, because the bias is fixed, there is no capacitor at the grounding point, so there is no distortion in the low frequency range.
In addition, the feedback is limited to 12 dB, which is relatively shallow for the Williamson type, and the distortion is suppressed without losing the energy of the input signal.

The OY-36 is reproduced and used for the output transformer.
The reprinted version of the OY-36 uses the same core and coil, and a copper shield plate is inserted to shield the core and ground potential, thus improving the mounting method and packaging.

The output terminal is designed only for 6 Ω to avoid degradation of sound quality caused by setting many taps.

A newly designed power transformer is used for the power supply circuit, and it is sealed in a case to avoid power flux.
The circuit configuration consists of double-wave rectification for both high-voltage and bias circuits. The high-voltage winding is rectified using 5U4GB, which is advantageous for voltage fluctuation. The winding for the heater is separated for each stage to reduce mutual interference caused by the heater. In addition, all ignition is AC.
In addition, a condenser input with a choke is adopted for the filter circuit, and the advantage of the condenser input is taken advantage of by the choke with good voltage efficiency and excellent regulation.

The chassis is 1.6 mm thick with copper plating on the entire surface to clarify the grounding for quick elimination of partial potential. In addition, no circuit boards are used except for the attenuator and line phase sensor, and all of them are directly wired.
In addition, the FRP chassis cover stabilizes the chassis and eliminates internal and external vibrations.

Custom capacitors are used for most of the capacitors. Electrolytic capacitors are custom-made and resistant to 550 v. Large carbon film type is used for the resistor.
In addition, high-quality wires are used for internal wiring.

The rear panel is equipped with input level control using a 12-contact rotary switch with fixed resistance switching.

High-quality pin jack with direct gold plating under copper without nickel plating base is used for input / output terminal.

A large vise type speaker terminal is adopted.

Equipped with line-phase sensor.

There was a special bonnet cover sold separately.

Model Rating

Type	Tube type monaural power amplifier
Rated output	45W (6 Ω)
Total harmonic distortion factor	0.1% or Less (1 kHz, 1W)
Frequency characteristic	5 Hz to 30 kHz (-1dB or less, 1W)
Input Sensitivity / Impedance	0.8V/60k Ω
Signal-to-noise ratio	90 dB or more
Vacuum tube used	KT-88 Super : 2 6CG7 : 1 Piece 12BH7A : 1 Piece 5U4GB : 1 6X4WA : 1 Piece
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	120W 170W (at rated output)
External dimensions	Width 220x Height 175x Depth 455 mm
Weight	17.0kg
Sold Separately	Bonnet Cover BMA-88 (¥ 40,000)