Yamamoto Sound Craft A-08S WE101D/104D single stereo amplifier

It is a WE101D, WE104D exclusive model with even smaller output than the highly rated WE205D. Although the output is less than 1W, it is an amplifier that realizes excellent sound quality not less than WE205D.

The WE101D flows the 13.5mA at a plate voltage of about 250V, and the load impedance 5kΩ is designed to ensure approximately 0.6W output. Power consumption is about 3.5W. On the other hand, the WE104D specification is to obtain up to 0.8W output at plate voltage 190V as standard. In both cases, the plate current tweaks the cathode resistance and sets it to the optimum value. We realize about 0.8W output as standard. In addition, both WE101D and WE104D can be used simply by switching cathode resistors.
The appearance of WE101D and WE104D is very similar, but their characteristics and sounds vary greatly, and it is well understood that they are vacuum tubes with completely different personalities. Compared to 's masculine powerful and energetic sound, is a feminine, gentle soft sound. When comparing the two, the gain difference is large and the volume of the preamplifier must be significantly changed. When listening in the same position, the volume is too different and the WE104D sounds like it is not powerful. As an impression, the WE104D is a little less gain, so it seems that the result is better to use about 2.5k ohm for the output transformer.

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I felt that the impression of the amplifier using the WE101D was the most dynamic and clear sound of all amplifiers such as WE205D, 45, 300B, etc. except when it was loud. This seems to have a large influence on the nonchalk power supply of this amplifier. Normal amplifiers use a chalk coil to remove the ripple of the B power supply in the output stage, but this amplifier provides a B voltage by forming a filter with only CR without using a chalk coil because of the small current used.

The usage of Darebone's lug terminal type polypropylene capacitor in the output stage of the cathode bypass capacitor in the output stage is similar to our bakelite case using a type enclosed with high strength epoxy resin. In addition, the vacuum tube called Siemens C3m is used as the driver tube by removing the shield case. The C3m is a relatively new five-pole tube, released around 1968, with very good characteristics, clean sound and low noise.

Both WE101D and WE104D were tested with the ST type and tennis ball type, where the ST type produced a well-defined tight sound, and the tennis ball type had a generous and relaxed sound. The tennis ball type looks interesting and enjoyable to see, but it is expensive, so I felt that if we choose based on sound quality, the ST type is more than sufficient. The speaker terminals are only 8Ω output terminals, but there are no issues using 4Ω or 16Ω speakers. However, in any case, the maximum output will decrease. At a maximum output of 8W, it will be about 4-6W.