PMG Signature · Reference

The new M400
Monoblock.

Reference-class monoblock power. The M800's design DNA, scaled for the systems most reference listeners actually live with.

400 watts · 4Ω Power
30WClass A bias >500 kHzBandwidth 60%In Class A
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PMG M400 Monoblock
  • PMG M400 Monoblock
  • PMG M400 Monoblock
  • PMG M400 Monoblock
  • PMG M400 Monoblock
href="/products/pmg-m400?variant=51635812696354" class="link" >PMG M400 Monoblock

Reference-class monoblock power. The M800's design DNA, scaled for the systems most reference listeners actually live with.

The M400 is a stunning reference monoblock. Darren Myers's topology, with strikingly low overall feedback — the signal path stays open, the music's natural texture stays intact. 30 watts of pure Class A bias hold the amplifier in its purest operating mode across roughly 60% of typical listening. No crossover artifacts. No class-switching. No compromise. A state-of-the-art active power supply delivers current the instant the music asks for it: 200 watts into 8 ohms, doubling to 400 watts into 4 ohms — effortless authority on virtually any loudspeaker worth driving. Bandwidth exceeds 500 kHz. Distortion stays flat across the entire audio band. Hand-built in Boulder, Colorado, and engineered by Bob Stadtherr. The M400 doesn't reach for reference performance. It defines it.

Price is per pair
$17,998.00
PMG M400 Monoblock

Design

The M400 shares the M800's design DNA: Darren Myers's low-feedback topology, a state-of-the-art active power supply, 50W of Class A bias, and bandwidth exceeding 500 kHz — scaled for the room and the system most reference listeners actually live with. Engineered by Bob Stadtherr. Hand-built in Boulder, Colorado.

Application

Each monoblock delivers 200 watts into 8 ohms, doubling to 400 watts into 4 ohms, with Class A operation across roughly 60% of typical listening. Sold as a pair, the M400 partners gracefully with everything from high-sensitivity floorstanders to demanding modern transducers — without ever running out of headroom.

Class A purity

Every M400 carries 30 watts of true Class A bias. Across roughly 60% of real-world listening, the amplifier never leaves the purest operating mode. No crossover distortion, no class-switching artifacts, no shift in character with volume. The result is the kind of microdynamic resolution and natural texture that only sustained Class A operation can deliver.

Power scaled

200 watts into 8 ohms, doubling to 400 watts into 4 ohms — exactly what the M400's namesake implies. Clean power doubling into halving impedance is the signature of a power supply working as it should, with reserves to spare. Darren Myers's design achieves this without sacrificing the agility and transparency that defines the PMG Signature voice. A state-of-the-art active power supply delivers current on demand without sag or compression, regardless of what the music asks for.

The PMG disappears into the Music

What you don't hear matters as much as what you do. The M400 employs strikingly low overall feedback by design — a deliberate choice that keeps the signal path open and the music's natural texture intact. Distortion stays flat across the entire audio band, and bandwidth extends well beyond 500 kHz, leaving no audible coloration or phase artifacts to come back as fatigue. The M400 simply gets out of the way.

THD vs frequency

Laboratory measurements across representative loads.

8Ω load
4Ω load
No load

Why flat matters

For more than fifty years, almost every solid-state amplifier has shared the same quiet flaw: distortion that rises with frequency, beginning around 4 kHz and often climbing 20dB or more by the top of the audio band. On a highly resolving system, you hear it as hardness on cymbals and a glaze on the top octaves. The usual fix — wrapping the amplifier in heavy global feedback — pushes the number down, but flattens the soundstage and collapses the natural dimensionality of the music. Darren Myers refused that trade-off. The PMG Signature topology holds distortion remarkably flat across the entire audio band, with only the gentlest rise at the very top — and without the heavy feedback that two-dimensionalizes the sound. What the graphs show, your ears confirm.

Features

7 key features

200 watts into 8Ω, doubling to 400 watts into 4Ω

30W Class A bias

Bandwidth exceeding 500 kHz

Strikingly low overall feedback architecture

State-of-the-art active power supply

Designed by Darren Myers

Engineered by Bob Stadtherr

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Specifications

Technical details
Unit Weight 55.8 lbs / 25.3 kg
Unit Dimensions 16 in L × 17.5 in W × 8 in H (406.4 × 444.5 × 203.2 mm)
With feet & binding posts: 16.75 in L × 17.5 in W × 8.75 in H
Shipping Weight 68 lbs (2 units)
Shipping Dimensions 23.5 × 23 × 15 in / 596.9 × 584.2 × 381 mm (2 units)
Input Power Auto Voltage: 120VAC or 230VAC, 50 or 60 Hz
Power Consumption Standby (Ready): <2W  |  Idle: 220W  |  50W/4Ω: 320W
Fuses No user serviceable fuses
Audio Inputs RCA (Single-ended): 1 pair  |  XLR (Balanced): 1 pair
Speaker Outputs Silver Plated Binding Posts: 4 pair
Trigger Input: 3.5mm, 5–15VDC  |  Output: 3.5mm, 12VDC
Gain 26.2 dB
Sensitivity 2.0V
Power Output 200W into 8Ω, 400W into 4Ω (1kHz, <1% THD)
Class A Power Output 30W into 8Ω
Frequency Response <10Hz – 80kHz (±0.25dB)
Input Impedance 100kΩ Single-ended  |  200kΩ Balanced
Bandwidth >500kHz
THD <0.002% typical (20Hz–20kHz, 1W/8Ω)
Damping Factor >300 at 8Ω (20Hz–1kHz)

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