Yamamoto Sound Craft A-03S KT88/6550 Direct connection single stereo power amplifier

A-03S is a single stereo power amplifier that uses KT88/6550, the most popular and easy-to-obtain five-pole vacuum tube, for the output stage.
The and 6550 are designed with the goal of delivering 100% performance and sound as a full-fledged single amplifier with a large vacuum tube that has a nearly identical rating this .
Standard attached output pipe is Tungsol6550.

The A-03S separates the plate circuit from the screen grid circuit in the output tube to obtain 12W/12W high output.
The circuit configuration adopts a direct connection method that has a reputation for sound goodness and circuit stability. A direct heat type 5-pole tube is used for the first stage, and it is directly connected to the output tube to obtain a sound full of dynamic feeling of reaction. The 1D5G of the first stage adopts a constant current point fire method, which stabilizes the bias voltage of the output tube by making constant current including the cathode bias resistance, and greatly improves the current stabilization of the output tube. This unit is equipped with a galvanometer that can check the current of the output tube so that it can easily replace various KT-88 and 6550 worldwide and enjoy comparative listening.
The power supply of the A-03S uses a power transformer, a cut-core transformer with orient core for the choke coil and an output transformer, and the output transformer succeeds in superior sound quality using insulated paper made of Teflon with excellent electrical properties.
In addition, the filter capacitor of the power supply uses a polypropylene film condenser with excellent transient properties and distortion rates for most parts to explore transparent sound. The charging and discharging time is much better than the general chemical capacitor, and the distortion rate of the capacitor itself is superior to the comparison. Even though it is a capacitor of the power supply part, the sound quality appears as a playback sound as it is. The use of this film condenser greatly contributes to this machine's clear and superior characteristics.
In order to efficiently supply the large current of the KT-88/6550, the 5U4G is used for the rectification tube of the output stage.

Other parts also use many of the finest parts. Dale's no-induction winding resistance, pure copper shaving speaker terminals, 3P power input terminals, luxurious champagne gold chassis and transcovers, etc. Magnetic distortion is expelled by the solid wood frame made of cherry and the total non-magnetic material structure by aluminum material.
The high-current and high-voltage parts are configured to satisfy the sound quality by using ultra-thick glass epoxy substrates called 2.0mm thick.