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Vacuum Tube Power Amplifier A-09S : Yamamoto




Non-feedback system single amplifier which adopted as the output tube 300B which occupies the status as a reference pipe of a present-day tube amp

A-09S is the power amplifier of the single stereo system which adopted famous 300B as the output tube.

The basic circuit has adopted the self-bias system of CR combination which uses pentode for a voltage amplification 300B single stereo amplifier A-09S.

In the amplification part, the natural acoustic field has been obtained taking advantage of the merit of the basic characteristic without the negative return with the non-feedback system.

The outstanding sound which carried out the one rise in ranking with the amplifier of conventional by re-examination from refinement of the ignition system of 300B or a drive circuit and the foundations of the parts to be used was realized.

SKU: Vacuum tube poweramplifier A-09S Categories: , Tag:


A novel and beautiful design is realized for a woody system material in combination with adoption and a champagne gold aluminum alloy transformer cover on a chassis.

A woody system material called the complite of 18mm thickness is adopted as the chassis of this machine.

This material is a material excellent also in intensity and electrically which laminated the thin single plate of cherry tree material and poured in and hardened phenol resin.

The intensity, and heat resistance and electrical insulation properties have the performance equivalent to phenol resin.

Moreover, the aluminum alloy of 2? thickness which gave alumite plating excellent in the side board and durability made from cherry tree material is adopted as a transformer cover, and it is made beautifully.

The socket made from inhouse Teflon currently evaluated highly by high performance and high reliability from all over the world is adopted extensively.

The tube socket of our original currently evaluated highly by the merit of the reliability and sound not only the inside of Japan but overseas is extensively adopted as these machine sockets.

The body of the socket of our company plates the Teflon excellent in temperature characteristics and an electrical property with gold at the round pin of the next door bronze manufactured by cutting, and is using it as the reliable socket at adoption and a pin.

All the pins have structure which begins to be deleted from the round bar of next door bronze, puts in a slit, and holds the leg of a vacuum tube exactly.

Therefore, where a vacuum tube is put to a socket, the leg of a vacuum tube is held firmly, there is no shakiness of a vacuum tube, and there is an effect which prevents the influence which external vibration has to a vacuum tube.

The poly pyrene film capacitor with little distortion [ product / with a sufficient sound / made by DALE / capacitor / adoption and] by a main part is adopted as resistance.

The resistance currently used for A-09S has adopted the product made by U.S. DALE as almost all portions.

To the large-sized resistor, metal tunic resistance and large-sized surface mount type resistance are properly used [ the metalclad type of the unguided type ] for the winding type highly precise in an inside capacity type at the type of small capacity.

It excels, so that the sound quality can compare neither with the thing of the domestic class by the same product made by DALE.

moreover, the reliability is also markedly boiled for the parts made according to U.S. MIL specifications and standards, and is high.

Moreover, the polypropylene capacitor is mainly adopted as a capacitor.

This polypropylene capacitor is excellent in the response to the signal of that palace nature compared with the usual chemical capacitor, and a capacitor’s own rate of distortion is also very excellent.

Since the difference in the sound quality in this capacitor influences greatly not only in a signal circuit but in a power supply circuit, it has measured the improvement in sound quality by adopting a polypropylene type for the capacitor of most including a power supply circuit.

Although the characteristic of these capacitors is very excellent, it has a weak point where foil resonates easily, only for the state which rolled round the film.

Therefore, in A-09S, filling adhesion of these polypropylene capacitors is carried out with the epoxide resin adhesives of high intensity at its company at the case of an ebony or bakelite, and the increase of the intensity of a capacitor and sound quality are raised further.

– Adopt the original pin jack of our company of chromium copper adoption as an input terminal, and adopt the speaker terminal made from pure copper as a speaker terminal.

The input terminal of this machine has adopted the highest-class pin jack of our original which chromium copper began to delete to an external conductor, adopted the round pin terminal of next door bronze shaving 出し as the internal pin for the terminal, and adopted Teflon as an insulation material.

pure copper shaving appearance was carried out to the output terminal, and I have adopted the large-sized terminal of Teflon insulation by gilding.

It is using at this that the thick thing speaker cable to 8mm diameter is also connectable.

The beautiful very hard African ebony round bar of sound is adopted as the leg.

By the beautiful thing of sound, it was begun to delete acknowledged African ebony material to the leg of this machine, and it is adopted as it.

This African ebony material is a material which has obtained evaluation beautiful sound for the material actually used for oboe or a clarinet and high also as arrangement base material of our company.

It is fixed to the chassis made from a direct complite, and the leg supports the whole weight exactly in order to obtain the merit of intensity and sound.

A quality wire rod is adopted as a power cable, and a hospital grade gilding terminal is adopted as a plug.

The power cable of this machine has adopted the hospital grade plug of Matsushita Electric Works as adoption and a plug part for the quality cable with the inlet terminal of 3p.

The gilding plug pin of special make is adopted as the pin of the plug.

Moreover, since I have adopted 3p inlet jack as the main part side, exchanging for the code of Mr. User’s hope is also possible.

If the quality of a tube amp improves, change of the sound quality by a power cable will come to appear sensitively.

Please also enjoy change of the sound by a power cable.


Form: 300B single stereo power amplifier

Use vacuum tube: 300B 2pcs. C3m 2pcs. 5U4G 1pc. (a standard is without Output tubes)

Maximum output: 8W+8W,

Frequency characteristic: 15 to 22 kHz (-3dB)

Residual noise: 0.6mV

Input impedance: 200kohm

Weight: — 18.8kg

Outside dimension: — 500 (W) — 294 (D) — 208 (H)

Additional information

Weight 18.8 kg
Dimensions 0.500 × 0.294 × 0.208 cm