LUXMAN M-05

Commentary

Stereo power amplifier with twin monaural configuration.

In the circuit system, true class A operation by the direct method of fixing bias current is adopted, and a large output of 105W + 105W is realized.
In addition, by adopting a large heat sink block of original design and a fan with low operating noise, high quality power is obtained with plenty of margin.

The M-05 uses a single-stage amplifier developed from duo-beta technology.
Luxman's original duo-beta circuit combines an appropriate amount of NFB for sound quality with a DC servo that tightens the sound image from outside the audible band. In addition to improving performance in the open loop before applying NFB, a small amount of NFB is applied to improve the performance not only in pursuit of characteristics but also in music reproduction performance.
This duo-beta circuit eliminates the need for high open-loop gain, which is required when applying a large amount of NFB, and realizes a single-stage amplifier configuration without the second stage amplifier, thereby simplifying the circuit.

The adoption of a single-stage amplifier realizes two epoch-making improvements.
In conventional amplifiers, the second amplifier stage is an amplifier circuit with a reference to the power supply. Therefore, the power supply used as the reference for amplification fluctuates due to changes in the input signal, and the music signal is modulated. In addition, noise is induced from the power supply to amplify and reproduce the music signal. In the single-stage amplifier, this problem is solved completely by realizing an amplifier circuit with only a ground reference, and amplification with only a ground reference is realized.
In addition, in the amplifier circuit, a high frequency correction stagger is provided for each amplification stage. In the case of two stage amplification, the two staggers interfere with each other, which significantly deteriorates the freshness of music. However, this can be eliminated by one stage amplification.

In order to make the reference potential = 0 absolute, the common power supply and theoretical mid-point grounding are not left unattended, and the ground is thoroughly grounded. Moreover, since the impedance becomes high when grounding the wiring board, the chassis ground is directly grounded. In addition to simply grounding the chassis, the ground line for each stage is concentrated at one point to make it more perfect. This point is also the center point of the left and right channels.
The oxygen-free copper wire is used for the tumor part.

The pre-drive stage, the only amplifier stage, uses a single stage cascode bootstrap differential amplifier with dual FET. The driver stage and output stage are SEPP with three stage Darlington connection. The output element uses high-speed power transistors with excellent linearity in a triple push-pull configuration.

We have specially designed a large-capacity transformer for the power supply. The inside of this transformer is hardened with silica sand to prevent temperature rise. We have also ensured high quality by thoroughly managing the windings on both the primary and secondary sides.
The electrolytic capacitor uses two large-capacity capacitors per channel for which sound quality measures have been taken. In addition, the constant voltage circuit to the pre-drive stage and servo circuit is also provided with stable power and instantaneous power corresponding to sudden large signal input by the single-stage amplifier regulator.

Anti-magnetostriction measures have been taken, and the material is also used after careful consideration.
Copper plates are used for key points and are firmly fixed to the chassis. Other capacitors, resistors and wiring materials are all carefully selected for sound quality.

In addition to the normal stereo mode, it can also be used as a 400W monaural power amplifier with a BTL connection. In this case, a genuine inverter with an inverting input amplifier for BTL keeps the high quality.

By dividing the power cord into two parts, mutual interference via power supply is eliminated.

The speaker terminal is a specially designed large terminal.

There were an adapter for rack mounting and a wood case sold separately.

Model Rating

Type	Stereo power amplifier
Effective power	Class A : 105W + 105W (8 Ω, 20 Hz to 20 kHz, both channel operation) When BTL is connected (AB class) : 400W (A class up to 105W, 8 Ω, 20 Hz to 20 kHz)
Total harmonic distortion factor	0.008% or Less (8 Ω, Both Channel Operation) 0.01% (4 Ω, Both Channel Operation)
Cross modulation distortion factor	0.008% or Less (8 Ω, 60 hz : 7 khz = 4 : 1)
Frequency characteristic	10 Hz to 100 kHz (-0.5 dB)
Input sensitivity	750mV
Input impedance	Direct in : 300k Ω ATT in : 45k Ω
Signal-to-noise ratio (IHF-A corrected)	120dB
Attachment	Peak meter with peak hold (with meter OFF SW) Electro Static Speaker Connector Signal OFF switch 3-stage FAN switch Line phase sensor BTL connection switch Subsonic Filter (15 Hz, -6dB/oct.) Input attenuator Warm-up mechanism Preheat mechanism
Protection circuit	DC drift detection speaker protection circuit Overcurrent detection amplifier protection circuit Temperature detection amplifier protection circuit
Pwer	100 VAC, 50Hz/60Hz
Power consumption	540W (Electrical Appliance and Material Control Law)
External dimensions	Width 460x Height 210x Depth 437 mm
Weight	40kg
Sold Separately	Dedicated Wood Case W-05M (¥ 60,000) Rack Mount Adapter LM-05M (¥ 15,000)