Audio Database


This is a tube type stereo power amplifier using the old famous ball 300B.

A 3-pole amplifier tube, 12AU7, is connected in parallel to the first stage. This reduces the output impedance and allows sufficient current to flow, ensuring a lower distortion factor than the amplification factor.

The driver stage uses 12BH7A in parallel connection.
12BH7A is a vacuum tube capable of handling a large current with low internal resistance even if it is a single tube. By using this in parallel connection, high reliability is ensured and 300B is driven with a margin.
The ATM 300 is a 3-stage configuration with a 3-pole tube.

In the output stage, 300B is a pure class A operation by self-bias.
In addition, due to heater hum noise peculiar to direct heating tubes, the heater is DC ignited and adjusted to the minimum point on measurement by variable resistor.

The output transformer is manufactured by tamura with a reputation. The condenser is Sprag, OS Con, Air Tight special block condenser, Riken RM carbon resistance, metallic coating, enamel, DALE metal clad. The socket is Cinch and Luxe. The output terminal is WBT. The wire is Verden. Pure copper single wire (6N) is used for each part.

The chassis structure is copper plated on the amplifier and bottom plate to eliminate magnetic strain.
At the center of the chassis, the top plate and bottom plate are connected by a stand and are received by a separate leg to ensure sufficient strength.

Printed circuit board which affects sound is eliminated and finished by hand wiring.

Equipped with a bias check meter, the 300B operation status can be checked immediately.

Equipped with a 3-stage damping factor control function, it is compatible with a wide range of speakers.

The early products used 300B made by Western Electric, but it seems to use 300B made in Russia after 2004.

Model Rating
Type Stereo power amplifier
Effective power 8W + 8W (8 Ω)
Input impedance 100k Ω
Vacuum tube used Western Electric (WE) 300Bx2 (initial)
Made in Russia 300Bx2 (since 2004)
5U4GB JAN Philips ECGx1
Accessory function Bias check meter
Damping factor control
External dimensions Width 430x Height 275x Depth 245 mm
Weight 24kg