Audio Database

Image of M5a

Class A non-feedback monaural power amplifier.

In M5a, about 90% of all parts are custom-made, and each part is handmade by dedicated staff.
Careful quality control is carried out, and every product is tested by a dedicated tester for one by one. Moreover, it is aged by 72 hours (3 days) by actual music signal.
In addition, two products selected at random from the finished products of each lot are delivered to the development staff for thorough listening, analysis listening, analysis and examination, and their quality is recorded in strict checks and history cards, also known as medical records.

Returning to the starting point of the amplifier of "faithfully amplifying an input signal and reproducing it as an output signal", we have developed and introduced a new super linear circuit which can obtain excellent characteristics without using NFB.
As a result, dynamic strain such as TIM strain is fundamentally eliminated, and stability over a wide area is ensured.

It is a class A operation amplifier that does not cause switching distortion or crossover distortion in principle.
In order to supply high power while maintaining A-class operation, a dedicated power supply for A-class bias is provided to efficiently extract the reproduced sound.
In addition, since the power supply efficiency is improved, there is no transient heat generation, which is a drawback of A-class amplifiers, and there is no need for cooling fans.

The power transformer employs a large-capacity toroidal transformer that provides low leakage flux and stable regulation.
The windings are made of oxygen-free copper wire coated with polyester, which has a cross-sectional area twice that of the conventional wire. This improves regulation and reduces the temperature rise of the windings to 1/2.
In addition, the adoption of the toroidal method, which is effective in reducing leakage flux, has achieved a remarkable S/N factory.
In addition, the transformer case is made of non-conductive and non-magnetic resin, and is filled with silicon carbide powder, which is a radio wave absorber, so that distortion and noise are suppressed by double and triple arrangements.

In addition to improving the high-frequency characteristics, we have adopted a film capacitor for pure audio to prevent noise and violent noise in the middle and high frequencies caused by the structure of the film capacitor.
The film is made of a composite structure consisting of polycarbonate with low dielectric loss and polypropylene with high insulation and excellent high-frequency characteristics. It is wound tightly at low speed and high tension to eliminate wrinkles and stress. In addition, a special winding core and heat-shrinkable resin are used to prevent singing.
In addition, in order to prevent the influence of external electric field, it is double shielded by conductive resin case and conductive resin tube.

Equipped with a 4-core power cord for audio, which was developed based on the fundamental study of the power cord.
By using oxygen-free copper with high conductivity for conductors, losses in wires are reduced and non-linear strain is greatly improved.
In addition, mutual interference between the two power transformers is suppressed, and power source impedance is improved. In addition, loss is reduced by using polyethylene with low dielectric constant for insulation, and conductor vibration is prevented.

Glass epoxy boards are used for printed circuit boards.
By using 99.99% pure oxygen-free copper and 280 μ thick copper instead of the conventional 35 μ thick, non-linearity is greatly improved, and the conductive resistance is reduced to 1/8, enabling loss-free and stable signal transmission.
In addition, since this substrate has excellent moisture resistance, the change in capacitance inside the copper foil is minimized and leakage inside the circuit is prevented. The characteristics such as crosstalk between input and output, S/N and distortion are also improved.

Non-magnetic aluminum is used as the structural material of the chassis to eliminate magnetic distortion which causes noise.
In addition, we have adopted a thorough vibration isolation structure such as the adoption of resonance dispersion type heat radiation fins and floating mounting of transformers through rubber dampers.

In order to prevent the fuse from adversely affecting sound quality, we have adopted an audio fuse whose material has been carefully studied.
The mouthpiece material has been changed from conventional brass to pure copper, reducing the conductor resistance to approximately 1/3 and greatly improving non-linearity.
We have also adopted tin plating, a non-magnetic material, in place of nickel plating, a magnetic material, to eliminate magnetic strain.

In addition to the unbalanced input, a dedicated transmission circuit is provided on the hot and cold sides, and a balanced input that cancels out noise components by inputting signals of opposite phases to each other.

In order to connect extremely thick speaker cables easily, it is equipped with a large speaker terminal of a vise crimping type with gold-plated contact surface.

Model Rating
Type Class A non-feedback monaural power amplifier
Effective power 300W (8 Ω, 20 Hz to 20 kHz)
Input sensitivity Unbalanced : 1.5 v
Balance : 1.5 v
Input impedance Unbalanced : 50k Ω
Balance : 600 Ω
Power display Peak level meter
Power consumption (Electrical Appliance and Material Control Law) 400W
External dimensions Width 438x Height 203x Depth 417 mm
Weight 26.3kg