Yamamoto Sound Craft
YDA-01B tube D/A converter

Bringing out the charm of the sound of WE pentode tubes

Designed for use with two Western 408A pentodes
Western Electric's WE408A high-performance pentode is used as the vacuum tube, and the output of the DA converter is loaded with a resistor and directly connected to the input of the vacuum tube to create a single-stage, single non-reduction amplifier. Current to the screen grid, which greatly affects sound quality, is supplied through a constant current circuit using MOS FETs to improve sound purity. The heater circuit uses large Schottky diodes to rectify both waves and supply the left and right sides independently. The design policy of minimizing the number of elements used was adopted to simplify the circuit and maximize the purity of sound.

PCM1794A DA converter IC in monaural configuration

The PCM1794A DA converter IC has four outputs for operating outputs in monaural configuration, but only one of these outputs is used, and dummy resistors are added to the other terminals so that they are not used. At first glance, this may seem like a wasteful use, but the sound is purer than the parallel connection.
Supplying power from individual regulator circuits eliminates interference to the circuitry by the power supply.

A large-capacity toroidal transformer is used for the power supply transformer, with independent windings for analog and digital circuits to minimize interference between them. The transformer is carefully designed to supply power from separate regulators for the digital, analog, and output circuits. For wiring materials, Teflon-insulated, silver-plated copper wires are used, which are extremely reliable and offer excellent sound quality.

Digital input terminal	1 coaxial (RCA)
Analog output terminal	Coaxial 1 channel (RCA)
Output level	4V/0dB
Tube used	WE408A x2
Supported frequencies	32~192kHz (automatic tracking)
Sampling Filter	8x oversampling digital filter
Frequency Response	20~20kHz(±1dB)
SN ratio	78dB (IHF-A waght)
Output impedance	2.6kΩ
Size	420(W)290(D)94(H)mm/5.2kg

The reason why the WE408A bulb was used to characterize this unit is not only for its simple tube-like flavor, but also because of the intention to actively reflect the characteristics of this pentode tube. For example, the amount of information and range of the high frequency range are similar to those of the transistor type.YDA-01The transistor version of the YDA-01, for example, has more information and range in the high-frequency range. Conversely, however, the transistor tubes seem to bring out the best in the thickness of the low-frequency range and the energy balance of the low-frequency range. In particular, the thick tone with power in the low frequency range may be largely due to the WE tubes.
The difference is easy to hear when listening to jazz music. The wood bass has the same blur-free touch and deep pitch, but the resonance is thicker and the body resonance is thicker. The same can be said for the tone of the piano and the instantaneous force of the kick drum. The same can be said for the tone of the piano and the instantaneous force of the kick drum. In the orchestra, too, the heavy resonance of the bass strings lowers the center of gravity, and the strings and woodwinds have a rich, lush, and sharp sound.YDA-01The YDA-01 is characterized by its instantaneous crispness and clarity of intensity and weakness, in contrast to the delicate softness of the YDA-01. If you want to listen to music with a modern, well-rounded response, theYDA-01should be called the orthodox version. However, if you are not satisfied with that, and seek a certain passion and strong expressiveness in your music, the YDA-01B model seems to show its appeal. It should be noted that this is by no means an "old sound. Its basic performance, supported by a high-precision device and a powerful power supply, guarantees the accuracy of its reproduction ability.
*STEREO SOUND