Yamamoto Sound Craft HA-02 Vacuum tube headphone/speaker amplifier

For the amplifier tube, only one miniature vacuum tube called Western Electric's 408A is used, one on each side. A 300mW output is sufficient for a headphone amplifier. In the case of a speaker system, it is also possible to listen to music at a lower volume with this output. The 408A also has excellent noise characteristics and excellent resolution at low volumes. Therefore, for BGM, it can be said that the advantage is that the sound is clearly reproduced even when the volume is reduced. Taking advantage of the large amplification factor of the pentode, it is composed of only one stage amplification circuit, and has succeeded in maximizing the freshness of the sound.

The output transformer of this unit uses a high-performance output transformer equivalent to that of high-end model transformers, Teflon insulated paper, and aims for the best sound quality. On the secondary side of the transformer, there are two types of terminals, one for a 50 ohm headphone amplifier and the other for an 8 ohm speaker.

The input section of the HA-02 is equipped with two terminals so that CD players, music players, etc. can be connected, and can be switched using a selector switch on the top of the chassis. You can use the included cable to connect most portable devices such as i-pods. The HA-02 is also recommended for working or studying while connecting these portable devices and playing speakers as background music. When the HA-02 is used for headphones, the optimum load impedance is 50 Ω, but it can be used for headphones with a wide range of impedances from 8 Ω to about 600 Ω.

The input terminal of HA-02 uses our original chrome copper Teflon-insulated pin jack. In addition, the speaker terminals use gold-plated high-grade terminals that can connect speaker cords up to 5 mm in diameter, and the headphone jack uses a highly reliable type made by Neutrik.

The chassis of this machine is made of Comprelite, which is also popular in A-08S and other products, and is a material with excellent electrical and strength because the wood is impregnated with phenolic resin at high pressure. In addition, the legs are made of African ebony wood, which is popular as a setting base and has a high seismic damping effect. In addition, a high-performance R-core transformer is used for the power transformer. For rectification, a fast soft recovery diode is used separately from the plate side and the screen grid side to bring out the good sound of the pentode. Film capacitors are used at key points in the power supply to create a high-quality sound power supply circuit.

Vacuum tubes used	WE408A 2 pieces included
Maximum Output	Headphone jack 300 mW (50 Ω load) Speaker jack 240 mW (8 Ω load)
Frequency response	30~21,000Hz (headphone jack) 45~17,000Hz (speaker terminal)
Residual noise	Headphone output: 100 μV, Speaker output: 70 μV
Input impedance	50k Ω
gain	Headphone output: 9.5 dB (50 Ω load) Speaker output: 1.5 dB (8 Ω load)
size	150(W)325(D)125(H)mm
weight	4.2kg

The HA-02 is as ultra-transparent as water, as if it does not exist as a regenerator. Listening sensitivity usually decreases during the session. To compensate for this loss, the film's soundtrack gets louder towards the end, which is why the HA-02 is forced to react in the opposite way. As the track progresses, the music feels louder. Why is this so? If you derive it from the experience you have gained from your ears so far, you will come to the weight of the low frequencies of amplifiers and speakers, which is usually said. How much does this have to do with the mids and low highs?　The amount of weight and density of the low frequencies projected into the vocal range is unusual. However, since it is different from the unnatural energy used to enhance the presence, such vocals do not bring with them the fatigue and enthusiasm of listening. Whether the bass is light or not does not determine whether the midrange is colorful. It has to do with the color temperature of the musical colors. The palette of HA-02 is incredibly rich, densely colored, and perfectly matches the aforementioned watery clarity.
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