Yamamoto Sound Craft HA-03 Vacuum Tube Headphone/Speaker Amplifier

The HA-03 is a unique amplifier designed to provide the best possible sound quality for both headphones and speakers. In the case of this amplifier, the configuration has been simplified to the utmost limit to maximize the appeal of the vacuum tube.

Simplicity makes the sound fresh and the music enjoyable.

The amplifier circuit of this unit is extremely simple.　Only one stage of C3m pentode tube, a vintage vacuum tube made by Siemens of Germany, is used as a pentode connection to bring out the proper amplification ratio and the best quality.　The circuit does not use negative feedback and employs the simplest and most natural non-feedback method. Using negative feedback improves performance, but the sound is often unnatural.

The number of components that pass through the system is reduced to the minimum to minimize sound degradation.　In this process, the screen grid circuit and plate circuit are separate power sources, and by making the screen grid circuit constant voltage, a large output power of approximately 1 W is obtained at a speaker load.

Maximum output power is 1.4W for headphones and 1W for speakers to handle a wide range of loads.

The HA-03 provides an output of 1.4W for headphones and 1.0W for speakers. 1W may seem small, but the output of a tube amplifier is said to be as powerful as that of a semiconductor amplifier with several times the output. Please try it out with your regular speakers to see how powerful it is. If your speakers have a certain level of efficiency, you will be able to enjoy a satisfactory sound up to a medium volume. The impedance of the headphones can also be accommodated in a wide range, from 16 ohms to 200 ohms.

Highly insulated reinforced wood is used for the chassis, and other high sound quality components are used.

The chassis of this unit is made of high-insulation, high-strength phenolic resin-reinforced wood, contributing to high sound quality. In addition, we use carefully selected high sound quality components from around the world, such as a large R-core transformer for the power transformer and wire-wound resistors made by DALE of the United States for the resistors.
The bright and vivid sound tone with no blurring and the ability to reproduce shades are attractive. The small bookshelf-type speakers are also attractive for their high-density, high-quality sound.

Tubes used	C3m (Vintage vacuum tube made by Siemens, Germany) 2 tubes 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 systems selectable
Size	156(W)330(D)165(H)mm
Weight	5.6kg

The headphones reproduce the sound with a smooth, yet clear reproduction of uneven surfaces and shadows. Although the range is not as wide as it could be, the contours are not blurred and the tone is bright and vivid. The touch of the piano is clear and thick, and the bass in jazz music is surprisingly robust and solid. The same is true of the speakers. It should not be too much to ask for bookshelf-type speakers in a small space. I used the SENNHEISER HD-650 and found it to have a satisfactory sound. The HD-650 is very versatile, so any headphones should be able to listen to it without any difficulty.