PS Audio has added two mono power amplifiers to its PMG Signature range: the Signature PMG M400 and Signature PMG M800. The new monoblocks follow the same engineering direction as the company’s recent Signature stereo power amplifiers, including Class A operation through the lower part of their output range.
Two new monoblocks in the PMG Signature family
The Signature PMG M400 and PMG M800 are positioned alongside the existing Signature PMG S200 and S400 stereo amplifiers, giving the range both stereo and mono options. While the stereo models are designed for conventional two-channel use from a single chassis, the M400 and M800 provide one channel per amplifier, allowing each loudspeaker to be driven by its own dedicated power amp.
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Power output and Class A operation
PS Audio lists the Signature PMG M400 at 1 x 400 watts into 4 ohms and 1 x 200 watts into 8 ohms. The larger Signature PMG M800 is rated at 1 x 800 watts into 4 ohms and 1 x 400 watts into 8 ohms.
Both mono models also operate in Class A at lower output levels. According to the stated specifications, the M400 remains in Class A up to 30 watts, while the M800 extends that Class A operating window to 50 watts. That is a notable part of the design brief, as it means the amplifiers are intended to run in their linear Class A region for a meaningful portion of everyday listening levels, before moving beyond that range when higher power is required.
Current-controlled amplifier topology
A central technical feature of the PMG Signature amplifiers is their current-controlled topology. PS Audio credits the circuit architecture to Darren Myers, with refinement by Bob Stadtherr. Rather than being governed internally in the more typical voltage-driven manner, the Signature PMG amplifiers are controlled by current.
PS Audio specifies a slew rate of 200 volts per microsecond for the design, alongside distortion of less than 0.002%. To support that speed, the amplifiers use switch-mode power supplies. The company’s rationale is that the required current delivery for this topology calls for a faster supply approach than a conventional passive transformer-based arrangement can provide.
Wide bandwidth and low feedback approach
The PMG Signature design is also specified with bandwidth extending beyond 500 kHz and very low overall feedback. Those figures place the new mono amplifiers firmly in PS Audio’s upper-tier engineering program, where the emphasis is on speed, control and linear behavior rather than simply headline power output.
As with the stereo S200 and S400 models, the M400 and M800 combine high rated output with a lower-level Class A operating region. The S200 is specified at 2 x 200 watts into 4 ohms and 2 x 100 watts into 8 ohms, with 10 watts in Class A. The S400 is specified at 2 x 400 watts into 4 ohms and 2 x 200 watts into 8 ohms, with 5 watts in Class A. The monoblocks increase the available per-channel power while retaining the same broader design philosophy.
Build and availability
The PMG Signature series is hand-built in Boulder, Colorado. The M400 and M800 are therefore not a separate design offshoot, but an expansion of a consistent amplifier platform spanning four models: S200, S400, M400 and M800.
Pricing and availability information has not yet been announced in the supplied details. No USD price has been provided for either monoblock.
With the Signature PMG M400 and M800, PS Audio gives its latest amplifier platform a pair of mono options for systems that need dedicated single-channel amplification and higher output capability, while preserving the line’s current-controlled architecture and Class A operation at lower power levels.
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