Phasemation SA-1500 300B Tube Integrated Amplifier

Description

Phasemation SA-1500 300B Tube Integrated Amplifier

The Phasemation SA-1500 is a high-end 300B stereo integrated amplifier developed to bring the musical qualities of Phasemation’s reference single-ended tube designs into a more accessible integrated format.

Introduced in 2024, the SA-1500 is based on the design philosophy of the MA-1500 monaural amplifier and uses a single 300B output tube per channel operating in pure Class A.

Its fully triode, non-feedback architecture, 6SN7 driver stages, Lundahl output transformers and carefully engineered low-noise power supply are designed to preserve tonal richness, dynamics and spatial realism.

Pure Class A 300B Single-Ended Operation

At the heart of the Phasemation SA-1500 is the legendary 300B directly heated triode.

Each channel uses a single 300B output tube in self-biased, pure Class A single-ended operation.

This simple and direct circuit architecture allows the characteristic qualities of the 300B to remain intact, including natural tonal density, expressive midrange reproduction and fluid dynamic behavior.

The amplifier delivers a rated output of 9W per channel, making it particularly suitable for high-quality loudspeakers with appropriate sensitivity and impedance characteristics.

6SN7 Two-Stage Driver Circuit

The 300B output tubes are driven by a carefully designed two-stage amplification circuit using 6SN7 triodes.

Phasemation selected the 6SN7 for its stability, linearity and ability to drive the 300B while maintaining the simplicity of an all-triode signal path.

This combination is designed to provide stable speaker drive while preserving the natural character, microdynamic expression and tonal qualities associated with a single-ended 300B amplifier.

All-Triode Non-Feedback Architecture

The SA-1500 uses a completely non-feedback amplifier topology.

The two-stage 6SN7 driver section and 300B output stage are composed entirely of triode tubes, avoiding global negative feedback throughout the amplification path.

This approach reflects Phasemation’s wider amplifier philosophy, prioritizing transient integrity, natural dynamics and direct musical expression.

Lundahl Output Transformers

The output transformers used in the Phasemation SA-1500 are manufactured by Lundahl of Sweden, one of the most respected specialist transformer manufacturers in high-end audio.

Phasemation selected these transformers specifically for the electrical configuration and sonic objectives of the SA-1500.

Their role is particularly important in a single-ended 300B amplifier, where the output transformer directly couples the power tube to the loudspeaker.

A shared output terminal arrangement allows the SA-1500 to drive loudspeakers with nominal impedances from 4Ω to 8Ω.

Independent Left and Right Power Supply Chokes

The left and right channels use independent choke coils in the power-supply circuits.

This dual-choke architecture reduces interaction between channels and helps maintain stable amplification from extremely small musical signals through to higher output levels.

Greater channel independence also contributes to clearer spatial reproduction and a more stable stereo image.

Low-Noise Power Supply Design

The Phasemation SA-1500 incorporates several measures designed to minimize electrical and mechanical noise.

The high-voltage supply uses ROHM high-speed switching diodes together with choke filtering, while the 300B heaters operate from a dedicated DC power supply.

The main power transformer is mechanically isolated from the chassis using anti-vibration rubber derived from the engineering used in the MA-5000.

This helps prevent transformer vibration from reaching the amplifier chassis and contributes to a quieter operating environment for the tube circuitry.

DIRECT Mode for Power Amplifier Operation

The SA-1500 provides three RCA line-level inputs.

Input 1 can also operate in DIRECT mode, bypassing the internal volume control and allowing the SA-1500 to function as a dedicated stereo power amplifier.

This gives owners the flexibility to use the amplifier either as a complete integrated amplifier or together with an external high-end preamplifier.

Recommended Preamplifier: Phasemation CM-1500

For listeners who want to use the Phasemation SA-1500 in DIRECT mode as a dedicated stereo power amplifier, the

Phasemation CM-1500 Hybrid Passive Preamplifier

is a natural partner.

The CM-1500 uses Phasemation’s hybrid passive volume-control architecture, providing a highly purist approach to source selection and level control.

When the SA-1500 is operated through its DIRECT input, the CM-1500 can control the system volume while the SA-1500 functions as a dedicated 300B stereo power amplifier.

Together, the CM-1500 and SA-1500 create a complete Phasemation amplification system designed around signal purity, simplicity and musical expression.

Phasemation SA-1500 Specifications

Phasemation SA-1500 Awards

The Phasemation SA-1500 has received major recognition from leading Japanese audio publications for its single-ended 300B design and musical performance.

Recommended Upgrade: TAKATSUKI TA-300B Tubes

Official Information

For complete manufacturer specifications, technical details and current product information, visit the

official Phasemation SA-1500 product page
.