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Iconic Amplifier Continues to Lead

The original Momentum Mono Amplifier was the first product designed and manufactured by the company and the latest version, the Momentum M400 MxV Mono amplifier elevates this iconic design to its greatest height. The Momentum M400 MxV models feature techniques and topologies initially developed and implemented in the Relentless Mono Amplifier. This fullest expression of the Momentum circuitry is reflected in the new model name, MxV. Those with a physics background will recognize that MxV or Mass times Velocity is the equation for Momentum.

Advancements in Every Area

Every major section of the amplifier – power supply, input, driver, and output stages – have all been enhanced in this advancement. A new transformer winding pattern provides over 50% more current output from the same transformer footprint. This additional current offers greater headroom during dynamic passages. A reinvisioned input stage combines a brand new circuit topology with advanced components feeding the driver and output stages. Crucial to the new circuit are the bipolar transistors powering the front end of the amplifier. In the Momentum M400 MxV amplifiers, new devices deliver ten times the current and power of the original devices. These wider bandwidth, higher power components extend low and high frequency performance with reduced distortion in both frequency extremes. Energizing the driver stage is a new bias stability circuit providing a nearly 50% increase in operating bias. Increasing Class A operation directly correlates to better sound quality. However, there is a limit to bias level in any amplifier. With this new circuit topology and our unique Copper heatsinks, thermal issues are not a practical concern in the Momentum M400 MxV amplifiers. The new bias scheme ensures bias consistency, preventing excessive temperatures even under the greatest demand. Additional power transistors in the output stage reduce workload for each device. By minimizing stress on each individual device, the entire output section works more efficiently. The result is a richer, more dynamic, intimate presentation regardless of musical genre.

The final output stage features new output transistors that were originally sourced for the flagship Relentless Monoblock Amplifier. The high-output transistors used on the Momentum M400 MxV are among the fastest available. Using 26 on the Momentum M400 MxV amplifiers they run at a blistering 69 MHz, permitting the Momentum M400 MxV to achieve incredible bandwidth. Each transistor mounts with two stainless steel fasteners—a rarity among flat-package transistors—for maximum thermal transfer to the copper heat sinks. A capacitor/resistor network connected to the base of each transistor ensures stability even at high frequencies and with low-impedance speakers. Additionally, every output transistor is measured and only devices that match the required performance specifications are included in the production of Momentum M400 MxV amplifiers. As with all D’Agostino models, the Momentum M400 MxV amplifiers feature discrete, direct-coupled balanced circuitry, the most accurate circuit platform possible.

Power to spare

Defying its compact size, the Momentum M400 MxV is a powerhouse amplifier. The backbone is the new ultra-quiet 1,800VA linear transformer with almost 50% greater current output. This engine drives a nearly 100,000ⲙF capacitor bank resulting in 400/800/1,600W of power output into 8/4/2Ω speaker loads for the Momentum M400 MxV The Momentum M400 MxV amplifiers are capable of driving any loudspeaker to its fullest potential.

Innovative Cooling with Venturi Style Heatsinks

A critical element of any amplifier output stage is circuitry known as the driver section. In the new Momentum M400 MxV, this stage is a fully complementary design. Individual transistors are employed for the positive and negative halves of the musical signal. This nearly doubles the current drive necessary to maximize the enhanced output stage that follows. The new output stage takes this increased drive to boost the open loop gain by the same factor of two. The result is a sound that is more authoritative, richer, and more expansive.

Hand-built and individually tested.

Each Momentum M400 MxV monoblock amplifier is hand-built and individually tested in D’Agostino’s Arizona factory by our team of technicians and craftsmen.

Upgrading to the MxV performance

The new Momentum M400 MxV employs the same chassis as previous Momentum amplifiers. All generations of Momentum Mono amplifiers can be upgraded to the Momentum M400 MxV performance level. All electrical enhancements are included in the upgrade while the original metalwork is retained. Original Momentum amplifiers receive a new 400 Watt meter plate reflecting the power output increase included in the upgrade. Momentum M400 units already have this power increase and meter.

Frequency Response

1 Hz to 200 kHz, -1 dB 20Hz to 20 kHz, ±0.1 dB

Signal-to-Noise Ratio

115 dB, unweighted


Silver Black Custom Finishes Available Upon Request

Input Impedance

1 MΩ

Output Impedance



400 watts @ 8Ω 800 watts @ 4Ω 1,600 watts @ 2Ω


400 watts @ 8Ω 0.09% @ 1 kHz


1 balanced XLR


12.5 x 21.5 x 5.25 inches / 31.75 x 54.61 x 13.34 cm.


95 lbs.

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