The MA-1500 distils Phasemation's transformer-coupled valve-amplifier architecture into a 10-watt monaural design. A single PSVANE 300B output valve operates in self-biased pure Class A and is driven through a transformer-coupled Toshiba 6CG7 stage for stable loudspeaker control and the direct musical expression associated with a simple 300B circuit.

All-triode, non-feedback signal path

The amplifier uses 5814A, 6CG7 and 300B triodes throughout and applies no global feedback. Phasemation chose this arrangement to preserve dynamic contrast and expressive detail without adding unnecessary stages to the signal path.

Swedish Lundahl transformers

Lundahl interstage and output transformers are matched to the MA-1500 circuit. Parallel secondary windings in the interstage transformer support reliable transmission of very small signals, while independent 4-ohm and 8-ohm output terminals use the output transformer's separate secondary windings.

Separated power supplies

Two independent choke transformers distribute power separately to the 5814A/6CG7 input-and-driver section and the 300B output stage. This reduces interaction between small-signal amplification and the loudspeaker-driving circuit.

Low-noise valve operation

A 5R4G valve rectifier avoids semiconductor switching noise in the high-voltage supply. Choke-input rectification and a directly heated 300B supplied from DC complete the low-noise design.