Yamamoto Sound Craft A-08S WE101D/104D Single Stereo Amplifier

These are dedicated models for the WE101D and WE104D, which have even lower output than the highly rated WE205D. Although the output is less than 1W, these amplifiers deliver excellent sound quality comparable to the WE205D.

The WE101D delivers 13.5mA at a plate voltage of about 250V, and with a load impedance of 5kΩ, it ensures an output of about 0.6W. Power consumption is about 3.5W. On the other hand, the WE104D is designed to achieve a maximum output of about 0.8W at a plate voltage of 190V as per the standard. In all cases, the plate current is fine-tuned to the optimal value by adjusting the cathode resistor. It achieves approximately 0.8W output as per the standard. Furthermore, simply switching the cathode resistor allows both the WE101D and WE104D to be used.
The WE101D and WE104D look almost identical in appearance, but their characteristics and sound differ significantly, making it clear that they are completely different tubes with different characteristics. While the WE101D is characterized by its masculine, powerful and energetic sound, the WE104D gives the impression of a feminine, gentle, and soft sound. When comparing the two, the difference in gain is significant, so the preamp volume position must be significantly changed. When listening from the same position, the volume difference is too great, making the WE104D sound less powerful. My impression is that the WE104D has a slightly less gain, so using an output transformer around 2.5k ohms seems to yield better results.

Unbelievably sensational!!
The 101D is much better than a 300B; it’s the best amplifier so far.
The impression of the amplifier using WE101D is that, except when playing at high volume, it has the most lively and clearly defined sound among all the company’s amplifiers including the WE205D, 45, 300B, etc. This seems to be greatly influenced by the non-choke type power supply of this amplifier. In normal amplifiers, a choke coil is used to remove the ripple of the B power supply in the output stage, but this amplifier supplies the B voltage with only a CR filter without using a choke coil due to the low current usage.

The cathode bypass capacitor in the output stage also contributes significantly to the sound quality, using a type of polypropylene capacitor from Dearborn, USA, with lug terminals, enclosed in a bakelite case with high-strength epoxy resin. Additionally, this unit uses a Siemens C3m vacuum tube as a driver tube, with its shield removed. The C3m, released around 1968, is a relatively new design of pentode tube with very good characteristics, producing clean sound with minimal noise, making it an excellent vacuum tube.

Both the WE101D and WE104D tested the ST type and the tennis ball type, but I felt that the ST type had a well-tightened, tight sound, while the tennis ball type had a generous, relaxed sound. The tennis ball type has a fun shape that is enjoyable to look at, but since it is expensive, I felt that if you choose based on sound quality, the ST type is sufficient. The speaker terminals are only 8Ω output terminals, but you can use 4Ω or 16Ω speakers without any problem. However, in either case, the maximum output will decrease. For a maximum output of 8W, the output will be around 4-6W.