Yamamoto Sound Craft A-08S "45" Single Stereo Amplifier

The A-08S has a small output, but its sound quality is as good as the best 300B amplifiers. The A-08S is designed to provide the best sound quality when combined with high efficiency speakers. Both the driver tube 717A and output tube 45 use DC ignition. The noise level is sufficiently low for a single non-reduction system, and is in the range of about 0.3mV~0.7mV, a level that poses no problem when used with high-efficiency speakers. 80" is an older tube than the 5U4G and has a much smaller capacity and withstand voltage than the 5U4G, but it is an excellent rectifier tube that produces a very clear and distinct sound." The "45" and "80" tubes are not only the normal ST type, but also have a unique and gentle sound. Please experience the precious vintage sound.

For the rectifier of the heater circuit of the 717A and 45 vacuum tubes, a high-capacity Schottky diode from International Rectifier, Inc. of the United States is used. This diode was selected from among many diodes in the world by the company through audition, and has an extremely low impedance characteristic, and the rectification loss is kept as low as about 0.3V. The low insertion loss is reflected in the sound of the A-08S, which is so powerful that its small output cannot be felt.

The power transformer, output transformer, and choke coil all use cut-core transformers, which are used only in high-end, high-beam models with excellent regulation. Each transformer is impregnated with resin to maintain its performance and quality. In particular, the output transformer uses a custom-made 100 micron thick core material, wound with Teflon insulation paper, and a new improved winding method for the A-08S to improve frequency characteristics.
Most of the resistors used in the A-08S are made by DALE of the United States. Non-inductive metal-clad type is used for large resistors, wire-wound resistors are used for medium capacity types, and metal-clad resistors are used for small capacity types. All of them are made by the same DALE company, and their sound quality is so excellent that they cannot be compared with the same class of Japanese-made products. The reliability is also remarkably high because they are manufactured in accordance with U.S. MIL standards.

Polypropylene capacitors are mainly used for the capacitors. Compared to ordinary chemical capacitors, polypropylene capacitors have superior response to pulsed signals and their own distortion rate is also very high. Since the difference in sound quality of these capacitors has a significant effect not only on the signal circuit but also on the power circuit, we have improved the sound quality by using polypropylene type capacitors in many parts including the power circuit. In addition, the input capacitors of the power supply and the coupling capacitors of the signal circuit, which have the greatest influence on sound quality, are made of the company's original capacitors. These are film capacitors in ebony or Bakelite cases impregnated with epoxy resin to prevent vibration of the elements, thereby greatly improving sound quality.

The A-08S is equipped with an ammeter for direct reading of the output tube current. The switch on the right side of the meter allows switching between the left and right tubes and reading their current values. This is very useful for determining when it is time to replace the vacuum tubes." For a 45" vacuum tube, 35mA-43mA is standard, and when those current values reach 65-70%, it is time to replace the tube.

The input terminals use machined chrome copper outer conductor terminals and machined bronze round pin terminals for the internal pins, and Teflon is used as the insulating material. For the output terminals, large terminals machined from pure copper, gold-plated, and insulated with Teflon are used. Even a very thick speaker cable (8 mm in thickness) can be connected to this terminal. The speaker terminals are 8Ω output terminals only, but there is no problem using 4Ω or 16Ω speakers. In both cases, however, the maximum output power will be reduced; a maximum output power of 8W will be reduced to about 4-6W.

The legs are carved from African ebony, which is known for its beautiful sound. This African ebony wood is actually used for oboes and clarinets, and is highly regarded as a material for the company's setting bases because of its beautiful sound. The legs are directly fixed to the Compright chassis for strength and resonance, and the entire weight is accurately supported.

Type	45 Single Stereo Power Amplifier
Tubes used	2 x 45 (vintage made in U.S.A.), 2 x 717A, 1 x 80 all included as standard
Maximum output	2W+2W
Frequency Response	18-30kHz (at 1W output)
Input impedance	200kΩ
Size	400(W)294(D)204(H)mm
Weight	14.3kg

The mid and high frequencies are very rich and far from stale. Vocals and cymbals make the room ring like I've never experienced before. All things considered (beyond the mids and lows), the A-08S is the best sounding amp I've ever spent time with. I didn't find it to be as good as the Geminis or other good amps I have, however, when it came to low-frequency performance. The Yamamoto delivers more tonal music than any other amp I've owned. They intoxicate you with rich, deep tones of color, and the Yamamoto S never sounded monotonous, giving instruments and vocals presence, timbre, and sound image unlike any other amp I've owned. I tried all my tubes, including TJ mesh 45s, the new EML solid plate 45s, Radiotron Globes, and Cunningham ST type 45s, and was amazed at how good the Yamamoto sounded with every 45. The sound of the A-08S is much more musical, with complete silence in between, giving it a much more realistic feel than I had expected.
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