PMG Signature · Premium Stereo

The new S400
Stereo.

The PMG Signature voice in a more accessible stereo chassis.

400 watts/ch · 4Ω Power
PMG S400 Stereo
5W/CHClass A bias >500 kHzBandwidth 10%In Class A
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PMG S400 Stereo
  • PMG S400 Stereo
  • PMG S400 Stereo
  • PMG S400 Stereo
  • PMG S400 Stereo
href="/products/pmg-s400?variant=51635812827426" class="link" >PMG S400 Stereo

The PMG Signature voice in a more accessible stereo chassis.

The S400 is the PMG Signature Series in stereo form. Two channels of 200 watts each into 8 ohms, doubling into 4, drawn from the same state-of-the-art active power supply that drives the M800. The same Class A bias of 5 watts per channel keeps both channels in the most linear region of operation for the delicate parts of the music. The same bandwidth beyond 500 kHz, the same flat distortion across the audible band, the same strikingly low overall feedback.

A single chassis. A single power cord. Two channels of reference-quality amplification.

The S400 exists for the listener who wants the entire Signature Series experience without two boxes, two power cords, and two sets of cables on the floor. Nothing in the topology has been pared back. The chassis is the only thing that changed.

Designed by Darren Myers. Engineered by Bob Stadtherr. Hand-built in Boulder, Colorado.
$9,999.00
PMG S400 Stereo

Design

Darren Myers's PMG Signature topology in a stereo chassis: a state-of-the-art active power supply, 50W of Class A bias per channel, bandwidth exceeding 500 kHz, and a strikingly low overall feedback architecture. Engineered by Bob Stadtherr. Hand-built in Boulder, Colorado.

Application

100 watts into 8 ohms per channel, doubling to 200 watts into 4 ohms per channel, with Class A operation where it counts. Drives the loudspeakers most listeners actually own — from monitors to mid-sized floorstanders — with PMG Signature transparency.

Class A purity

5 watts of true Class A bias per channel — in a single stereo chassis. The S400 stays in Class A for the quiet passages of typical listening, eliminating crossover artifacts and the audible signatures of class switching. Both channels carry the same operating purity as PMG Signature monoblocks, in a footprint that fits where two chassis can't. The musical presentation never compromises for the format.

Two channels, one design

The S400 isn't a stereo amplifier with monoblock ambitions — it's a fully realized two-channel implementation of Darren Myers's PMG Signature topology. Each channel runs independent state-of-the-art active power supply rails, with mechanical and electrical isolation engineered to keep one channel from disturbing the other. The result is monoblock-grade channel separation in a single integrated chassis: 200 watts into 8 ohms per channel, doubling to 400 watts into 4 ohms per channel.

The PMG disappears into the Music

What defines a PMG Signature amplifier is what you don't hear. The S400 uses strikingly low overall feedback — a deliberate engineering choice that holds distortion flat across the entire audio band, with bandwidth extending well beyond 500 kHz. No phase smear, no recovered artifacts dressed up as detail. The music arrives whole, the amplifier disappears, and the loudspeakers tell the truth.

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 per channel, doubling to 400 watts into 4Ω per channel

5W Class A bias per channel

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 57.2 lbs / 25.9 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
Shipping Dimensions 23.5 × 23 × 15 in / 596.9 × 584.2 × 381 mm
Input Power Auto Voltage: 120VAC or 230VAC, 50 or 60 Hz
Power Consumption Standby (Ready): <2W  |  Idle: 190W  |  50W/4Ω: 390W
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/ch into 8Ω, 400W/ch into 4Ω (1kHz, <1% THD)
Class A Power Output 5W/ch 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 >240 at 8Ω (20Hz–1kHz)
Crosstalk >90dB at 1kHz

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