45 Vacuum tube Single Stereo Power Amplifier A-08SS

388,000yen (Build to order)

A-08SS is the single power amplifier which can be said also as the final edition of 45 vacuum tubes which arrived through A-08 to two improvement of the founder.
At the time of the founder's A-08, I had received prize for an excellent work in WEB magazine 6moons.
And I put A-08SS on the market as the last form through two improvement lately.
If A-08SS changes with the stereo amplifier of the two-step amplification from the former, and single operation as circuit composition, it is not.
fundamental circuit composition although it is the same with composition with the output stage of Western Electric 717A driver tube and 45 vacuum tubes, it is in the first feature of A-08SS having improved all use parts, and having raised the quality of the resistor and the capacitor to the limit.
It is rare to take up the thing of the characteristic not much with vacuum tube amplifier.
What the sound of very little semiconductor amplifier of the rate of distortion is actually inferior to a vacuum tube in in many cases is exactly that the vacuum tube has the sound which cannot be expressed at the rate of distortion.
However, also in vacuum tube amplifier, each part, structure component, etc. influence sound greatly, respectively.
In A-08SS, the cut core is used even for the power transformer which uses the cut core excellent in the regulation as succession from the former, the output transformer which uses a 100micro thickness Hi-B cut core, and a choke coil.
Especially, the fluoro-resin material with a low dielectric constant was used for the output transformer as an insulating paper of a coil, and the improvement in sound quality is measured.
Although metal is usually used for a chassis, in this machine, the compound material of a woody system called lamination compressed laminated wood is adopted.
That of this lamination compressed-laminated-wood is the material which phenol resin excellent in insulation was infiltrated into the thin single plate of cherry tree material, and carried out hot forming to it by high pressure.
Insulation has the characteristic equivalent to phenol resin, and intensity has the toughness which also endures phenol resin.
Although it looks similarly to wood in appearance, the characteristic is excellent in whether you are exlent.
It has succeeded in considering it as the chassis which does not have worries about resonance by high intensity in such lamination compressed laminated wood by turning off the screw directly or attaching parts.
Inside vacuum tube amplifier, the parts and wiring material into which much current flows exist.
If current flows, an eddy current will occur to a near metal.
It is also considered that the eddy current affects sound quality.
It is thought that it is effective that the chassis is made of an insulator also when losing such influence.
Also in vacuum tube amplifier, resonance of the vacuum tube and parts to be used and vibration influence sound delicately.
By high intensity, few chassis which cry think that it is important to high-quality-sound-izing.
Moreover, about the tube socket, the importance is felt from before, the fluoro-resin material which was excellent in insulation performance at its company is cut, a socket is produced, and the quality socket is produced and used combining the socket pin which began to delete phosphor bronze.
From before, you evaluate these sockets highly and they are used. It to the internal and external vacuum tube amplifier maker or the its original work amplifier builder.

The U.S. Vishay tabulation side mounting type thin film resistance which excelled resistors of the whole page main in the characteristic was adopted, and sound quality was raised.
Many resistors are used in vacuum tube amplifier.
Such a resistor was seldom conventionally verified about sound quality etc.
Since vacuum tube amplifier is manufactured for many years, the resistor used in it also has many old things, and many parts which are old and the characteristic does not yet have have been used.
At us, influence on the sound of such a resistor was investigated from before, and it traced that the resistor of sound with the sufficient characteristic is good.
Before, it turned out that especially a surface mount type thin film resistor is powerful, and sound quality is also excellent in the development process of developed head shell HSA-01 with built-in head amplifier.
Since use was difficult for the surface mount type resistor etc. for a product called vacuum tube amplifier as it was, the small substrate was made for exclusive use, and it changed so that it might be easy to wire, and the experiment was repeated.
Surface mount type thin film resistance is the small parts currently treated as what is called chip resistance.
Since the lead is not attached, it is hard to carry out wiring, but since there are no cap, junction of a lead, etc. in the usual resistor, in the portion, it becomes a merit in sound quality.
Since it is the parts developed as a use included in the highly efficient smartphone and electric device of recent from the first, the performance has the value which was very excellent.
Although the accuracy of the resistor used for the usual vacuum tube amplifier is 1% to 5% and the temperature characteristics are 50 ppm to about 500 ppm, it excels in the thin film resistor of Vishay currently used for this machine very much with the resistance error of 0.1%, and the temperature coefficient of 5 ppm to 10 ppm.
The temperature coefficient of the resistor expresses the change of resistance to 1 degree of rises in heat when current flowed and generates heat to a resistor.
If this temperature coefficient is not good, when exchange current, such as a music signal, flows, resistance will be changed, and sound will be influenced greatly.
Since a resistance error is a value including such a temperature change, the direction of a resistor with few resistance errors is also that it is good.
Moreover, if the quality of a resistor becomes good, the noise generated from a resistor is also reduced and low noise-ization of amplifier can also be measured.
The remains noise by a feeling of sound of this machine is actually decreasing sharply.
Since it is hard to treat resistance of this Vishay very small, it prepares a small board for exclusive use in the driver stage, and mounts the resistor there.
The minimum substrate is made at places other than the driver stage, and with 6N copper wire, as it can be wiring, it is used.

The ammeter is arranged in order to supervise the current value which flows into the vacuum tube which uses the meter unit for output tube current surveillance for an adoption output tubes.
If this current value turns into 60% to 70% of initial values, it will become the exchange time of an output tubes.
By the eye, the state of an output tube is in sight, and is known, and the life of a vacuum tube can be checked by the eye.
It is being dared to make the output terminal into 8 ohm only.
An 8-ohm terminal has come out of 1 set of speaker terminal of this machine.
However, the speaker from 4ohms to 16ohms can be used.
Since it will lead to a sound quality fall if a middle terminal is prepared in an output transformer, it is being dared to make the output terminal into 1 set.
Although a little maximum output falls by speakers other than 8 ohms, a sound has little change and it can be satisfactorily used for it.

The film capacitor was adopted as contest a cathode path of a driver tube and an output tubes.
In almost all cases, with vacuum tube amplifier, cemical capacitor has usually been used for the cathode portions of a driver tube and an output tubes as contest a path.
Since big capacity is obtained in size with small cemical capacitor, this is almost used for the latest vacuum tube amplifier.
however, the Western which should also be called starting point of audio amplifier around 1940 to the 1950s when the vacuum tube has been just developed contest oil being used for this cathode capacitor, when the electric 300B amplifier 91B was developed, and
The sound with a quality high with small capacity called 20-30uF had been obtained.
It has become like common sense that cemical capasitor can obtain now easily and it uses the capacitor of the big value of 100uF unawares.
Western although cemical capacitor did not exist in an electric time but that acquisition was also difficult had a capacitor of big capacity, contests oil currently used there seemed to be the parts of the considerably excellent sound quality.
At us, paying attention to the point, the cathode capacitor is transposed to contest a film which was excellent in the performance, and also the Africa ebony case is made as a resonance stop, and it is used, being filled up with an epoxy resin.
In the driver stage and the output stage, capacity adopted the value of 20uF.
This has obtained the speedy forcible sound.
Moreover, the film capacitor made from CDE chosen by many auditions is used for the coupling capacitor in front of the output pipe which influences sound greatly in the case made from the Africa ebony, putting it in.

A-08SS Specifications
Form : 45 single stereo power amplifier
Use vacuum tube: 45(U.S. vintage article) 2 product made from Western Erecriric 717A 2 80 rectifier tubes It is standard attachment altogether one.
Maximum output: 2W+2W
Frequency characteristic: 27Hz-30kHz (at time of 1W output +0, -3 dB)
Remains noise: 1.1mV
Gain: 18.6dB (it is 2W output at the time of 0.7V input)
Input impedance: 200kohms
Output terminal: Only 1 set 8-ohm
Outside dimension: 400(W)294(D)204 (H)
Weight: 14.3kg
Price: 388,000yen Build by order