Yamamoto Sound Craft
YDA-01B Vacuum Tube Output Circuit DA Converter

Bring out the charm of the sound of the WE pentode

Designed on the premise of using two Western 408A pentodes
Western Electric's high-performance pentode WE408A is used for the vacuum tube. A resistor is applied to the output of the DA converter and directly connected to the input part of the vacuum tube as it is, creating a single non-feedback amplifier with a single-stage configuration. The current to the screen grid, which greatly affects the sound quality, is supplied through a constant current circuit using MOSFETs to improve the purity of the sound. The heater circuit is a large Schottky diode that supplies both waves rectifier and left and right sides independently. We adopted a method of reducing the number of elements used to the utmost limit, which is a design policy, and simplified the circuit to maximize the purity of the sound.

Mono configuration of PCM1794A to DA converter IC

The output of the PCM1794A DA converter IC has a monaural configuration and has four outputs for operating output, but only one of the outputs is used, and the other pins are not used by adding a dummy resistor. At first glance, it may seem like a waste, but the purity of the sound is higher than that of a parallel connection.
Supplied from a separate regulator circuit eliminates interference with the circuit by the power supply

A large-capacity toroidal transformer is used for the power transformer, and the analog and digital windings are independent to suppress mutual interference. The transformer is a careful power supply circuit that supplies the digital part, the analog part, and the output circuit independently from a separate regulator. The wiring material is Teflon-insulated and silver-plated copper wire, which is extremely reliable and has excellent sound quality.

Digital Input Terminals	Coaxial 1 system (RCA)
Analog output terminal	Coaxial 1 system (RCA)
Output level	4V/0dB
Vacuum tubes used	WE408A x2
Supported frequencies	32~192kHz (automatic tracking)
Sampling Filters	8x Oversampling Digital Filter
Frequency response	20~20kHz(±1dB)
signal-to-noise ratio	78dB (IHF-A waght)
Output impedance	2.6kΩ
size	420(W)290(D)94(H)mm/5.2kg

I would like to think that the reason why we went out of our way to characterize the WE408A sphere in this unit was not only to give it a simple tube-like seasoning, but also to actively reflect this pentode. For example, the amount of information and range in the high frequency range are transistor-specific.YDA-01It can be said that it is more abundant. However, on the other hand, I think that the thickness of the low frequency range and the calm energy balance of the waist fully bring out the characteristics of the vacuum tube. In particular, the thick tone with power on the low frequency range may be largely due to the WE ball.
When you listen to jazz, it's easy to see the difference. There is no change in the unbleed-free touch of the wood bass and the depth of the pitch, but the resonance is a little thicker and the resonance of the thumping body is thicker. The same can be said for the tone of the piano and the instantaneous power of the kick drum. It's a kind of crisp impression. Even in an orchestra, the heavy sound of the bass strings lowers the center of gravity, and the strings and woodwinds have a lustrous sharpness along with the richness of moisture.YDA-01In contrast to the delicate softness of the film, it is characterized by an instantaneous crispness and clarity of dynamics. If you listen to music with a modern and well-organized response,YDA-01It should be said that it is orthodox. However, when you don't get tired of it and want a certain kind of enthusiasm and powerful expressiveness in your music, I think the YDA-01B model will show its appeal. It should also be noted that it is by no means an "old sound". The basic performance, supported by a high-precision device and a powerful power supply, guarantees the accuracy of the reproducibility.
*STEREO SOUND