Exclusive M7

Commentary

This monaural power amplifier is designed with the latest of the latest technology, and its performance has been refined to reproduce richer musical quality through repeated trial listening and attention to craftsmanship.

Class A operation without crossover distortion and switching distortion in principle is adopted. In addition, in order to improve drive performance at low load and to suppress generation of distortion, voltage and current amplification circuits are clearly separated.
A hybrid IC using an aluminum substrate is adopted for the voltage amplification stage, and high-precision voltage amplification is performed using NFB. The power amplification stage is 5-stage Darlington to ensure power linearity, the drive transistor is 2-parallel, and the power transistor is 6-parallel push-pull configuration, enabling current amplification with less distortion even though it is a non-feedback amplifier.
In addition, the voltage amplifier stage and power amplifier stage are separated from each other in terms of layout to eliminate mutual interference.

In order to prevent adverse effects on sound quality due to counter-electromotive force generated by external pressure applied to the cone paper of the speaker and high-frequency noise such as radio waves and fluorescent lights induced in the speaker cable
The voltage amplification stage and the power amplification stage are completely separated, and a circuit configuration without feedback loop from output to input is adopted.

Focusing on the fact that the output signal is obtained by modulating and synthesizing the two power supplies (plus and minus) with the input signal, we have adopted symmetrical construction that equalizes the internal environment and mechanical strength of the chassis, such as the temperature of the plus and minus power supply and the temperature and magnetism of the amplification stage.
This reduces distortion not only from the circuit, but also from temperature distribution inside the chassis, magnetic effects, and chassis mechanical strength problems.

In addition to the input terminal of the RCA pin jack, a balanced input terminal of the canon-type input jack is mounted on the input terminal.

The power supply section uses a large-capacity toroidal transformer that provides low linkage flux and stable regulation. The use of an extremely thick winding improves regulation and reduces temperature rise, contributing to stable temperature balance.
In addition, the two transformers are dedicated to the positive and negative power supply respectively, reducing the source impedance, and in combination with the adoption of the double-bridge rectification system, the speaker can be driven more accurately.

It employs a protective circuit that eliminates the relay from the output stage, reducing the effect of the protective circuit on sound quality and minimizing the contact points of the signal path.

In order to prevent the deformation of the chassis due to external vibration and internal heat from affecting the sound quality, it uses a strong structure that is hard to be deformed. In addition, thick aluminum material is used lavishly to ensure the strength and eliminate the influence of magnetism that causes distortion.
In addition, in order to suppress vibration, we have adopted a floating mount for the power transformer, and have taken thorough measures to prevent vibration and vibration.

In order to ensure the realization of the design concept of symmetrical construction, a large heat sink with high heat radiation efficiency is laid out in an appropriate position, and the temperature environment on the positive and negative sides is made uniform.

To prevent interference between circuits from affecting sound quality, each circuit section is separated by a shield to eliminate mutual interference.

In order to provide a stable power supply to the dedicated positive and negative transformers, a 6-conductor thick oxygen-free copper audio cord with high conductivity is used.
It is designed with an emphasis on sound quality such as double insulation, adoption of carefully selected coating material, polarity indication on plug, etc.

The speaker terminal is a large vise crimping type speaker terminal that allows for easy connection of very thick speaker cables. In addition, the connection is gold-plated.

Starting with parts such as transformers, transistors, ICs, and chassis materials, all parts are carefully selected and selected.
In addition, experienced testers listen to each carefully hand-made product, and even the sound quality that does not appear on the instrument is strictly checked. Only products that pass the check are shipped.

Model Rating

Type	Class A monaural power amplifier
Rated output	480W (2 Ω) 240W (4 Ω) 120W (8 Ω)
Input Sensitivity / Impedance	Input1 (Coaxial) : 1,0V/10k Ω Input2 (Balance) : 1.0V/2.2k Ω (3rd hot)
Output terminal	Speaker : 2 Ω ~ 8 Ω
Frequency characteristic	5 Hz to 100 kHz + 0 -1dB
Damping factor	100 (8 Ω)
Signal-to-noise ratio	120 dB (A network, short circuit)
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	440W (Electrical Appliance and Material Control Law)
External dimensions	Width 460x Height 220x Depth 441 mm
Weight	47kg