Yamamoto Sound Craft HA-03 Vacuum tube headphone/speaker amplifier

The HA-03 is a unique amplifier designed to be an amplifier that can be enjoyed with the best sound quality for both headphones and speakers. HA-03 has a simple configuration with a high-performance C3m vacuum tube amplified in one stage. In the case of this machine, the configuration has been simplified to the utmost to maximize the appeal of the vacuum tube.

Because it is simple, the sound is fresh, and you can enjoy the music.

The amplification circuit of this unit is extremely simple.　Only one stage of the pentode C3m, a vintage vacuum tube manufactured by Siemens of Germany, is used as a pentode connection to bring out the appropriate amplification factor and the highest quality.　The circuit does not use negative feedback, and uses the simplest and most natural no-feedback method. Using negative feedback improves performance, but often results in unnatural sound.

The number of passing parts is reduced to the utmost limit, and the degradation of sound is minimized.　Among them, the screen grid circuit and the plate circuit are used as separate power sources, and a large output of about 1 W is obtained with a speaker load by setting the screen grid circuit to a constant voltage.

Maximum output is 1.4W for headphones and 1W for speakers for a wide range of loads

The HA-03 has an output of 1.4 W with a headphone load and 1.0 W with a speaker load. The output of 1W may seem small, but the output of a tube amplifier is said to be as powerful as that of a semiconductor amplifier. Please check out the speakers that are usually used to see how good they are. If the speaker is moderately efficient, you can enjoy almost satisfactory sound up to medium volume. The impedance of the corresponding headphones can also be used for a wide range of headphones from 16 Ω to about 200 Ω.

The chassis is made of highly insulated reinforced wood, and other high-quality sound components are used.

The chassis of this unit is made of highly insulating and high-strength phenolic resin reinforced wood, contributing to high sound quality. In addition, we carefully select high-quality sound materials from around the world, such as large R-core transformers for power transformers and wire-wound resistors made by DALE of the United States for resistors.
The bright and vivid tone without blurring and the reproducibility with shadows are attractive. In addition, if you use a small bookshelf type speaker, you can enjoy dense and high-quality sound.

Vacuum tubes used	C3M (vintage vacuum tubes made by Siemens GmbH, Germany) 2 pieces included
Maximum Output	1.4W+1.4W (50Ω/headphone load) 1W+1W (8Ω/speaker load)
Frequency response	35Hz~17.5kHz(-3dB)
Residual noise	57μV (with A filter)
Input impedance	50kΩ input switching: 2 selectable
size	156(W)330(D)165(H)mm
weight	5.6kg

With the smooth yet clear reproduction of unevenness, you can enjoy a shadowy expression with headphones. It's not a way to get a wide range, but the outline is bright and vivid without blurring. The touch of the piano is clear and thick, and in jazz, you can feel the bass with a surprisingly solid feeling. The same goes for the speakers. If you listen to the bookshelf type in a small space, it should not be impossible. In any case, it is a product that you can enjoy a dense texture. I tried using the SENNHEISER HD-650 and it sounds good enough. It is highly compatible, so you should be able to listen to it with any headphones without difficulty.