Phasemation MA-1500 Vacuum Tube Monaural Power Amplifier

300B single-ended class-A monaural power amplifier with Lundahl interstage and output transformers

The Phasemation MA-1500 is a pure class-A, single-ended 300B monaural power amplifier designed to deliver the tonal purity, spatial depth, and harmonic integrity that define the 300B experience. Built on a rigid chassis with choke-filtered power supply, DC-heated 300B filament, and carefully selected triode stages, the MA-1500 emphasizes quiet operation, stable drive, and natural, emotionally expressive sound.

Its signal path uses an all-triode, non-feedback circuit (5814A input, 6CG7 driver, 300B output) with Lundahl interstage and output transformers for wide bandwidth and low distortion. A 5R4G rectifier tube suppresses switching noise, while a DC filament supply for the 300B further reduces hum. Separate 4 Ω and 8 Ω output taps ensure optimal matching with high-efficiency loudspeakers, making the MA-1500 ideal for systems built around nuance, timbre, and intimacy.

Specifications

Type: 300B single-ended monaural power amplifier

Rated Output: 10 W or more (THD 5%)

Frequency Response: 10 Hz–40 kHz (+0, -3 dB)

Input Impedance: 47 kΩ

Gain: 26 dB

Residual Noise: 200 μV or less (A-NET)

Output Impedance: 4 Ω, 8 Ω

Power Consumption: 100 W

Dimensions (WHD): 9.65" x 8.90" x 16.81" (245 x 226 x 427 mm)

Weight: 35.27 lb. (16 kg)