Draws out the music’s reality and the artist’s passion A 300B single vacuum tube type stereo integrated amplifier.
In the world of audio amplifiers, wide kinds of semiconductor amplifiers, tube amplifiers, etc. are released. Therefore, the respective audio features can be enjoyed as a hobby. The tube power amplifiers have a tube called "fine tube" having a reputation for sound quality and in 2017, Phasemation has released the monaural power amplifier, MA-1500 composed by a single-ended circuit adopting 300B which is the best tube among vacuum tubes and a circuit strongly driven by a transformer-coupled circuit. In 2024, in order to express this significance to a wider audience, we developed the SA-1500 stereo integrated amplifier with a single operation of a 300B single-tube and ensuring a 9W output.
The 300B output tube is a self-biased single pure class-A operation, and 6SN7 is used in a two-stage amplification circuit to demonstrate the original quality of the 300B in the simplest possible operation, driving speakers with unshakable stability
Two-stage 6SN7 +300B all-stage triode tube to achieve the dynamic and expressive music playing that is only possible with a non-feedback circuit
An output transformer manufactured by Lundahl of Sweden is used because it is appropriate for the configuration of this unit and has the most suitable sound quality that Phasemation is aiming for. A shared terminal is supplied to optimally drive the speakers from 4 to 8 ohms
The power supply circuits for the left and right channels are powered by independent choke coils, eliminating mutual interference between the left and right channels and providing clear amplification of signals from minute levels to high-power signals.
This is thoroughly designed for a low-noise; it is designed with a rectification circuit with a ROHM high-speed switching diode and choke transformer for the high-voltage power supply and the 300B heater using DC ignition with a DC power supply. Furthermore, the power transformer is floating from the chassis using anti-vibration rubber used in the MA-5000. This suppresses the transmission of unwanted vibrations to the chassis and contributes to further reduction of noise levels
Three RCA input terminals are provided. In addition, the “DIRECT mode” is provided on the “INPUT1” terminal. By selecting this “DIRECT mode,” the music signal passes through the volume control, allowing the unit to be used as a “stereo power amplifier” with even higher purity and a greater atmospheric expression.
| Product | 300B Stereo Integrated Amplifier |
| Input impedance | 47k ohms |
| Gain | 30dB |
| Residual noise | 200µV or less: A-NET |
| Rated output | 9W or more / 4 ohms (THD: 5%) |
| Frequency characteristics | 10Hz to 40kHz (+0,–3dB) |
| Output impedance | 4 ohms to 8 ohms |
| Power consumption | 140W（100VAC, 50 to 60Hz） |
| External dimensions (mm) | 430（W） x 240（H） x 380（D） |
| Weight | 18kg |
