Dan D'Agostino Stereo Amplifiers

Progression S350 Stereo Amplifier
Power and Performance

Leveraging Dan D’Agostino innovative Super Rail circuitry, the Progression S350 Stereo Amplifier exploits this unique technology delivering remarkable control and fidelity to any connected loudspeaker.

Every amplifier employs a voltage rail, actually two, a positive one and its companion negative partner. Voltage rails support the delivery of power to the speaker. The music signal swings between these two rails but due to natural loss, the musical signal never reaches the output rails’ full capability. Their Super Rail overcomes this limitation. Borrowing the idea of a turbo in a car engine, the Super Rail employs higher voltage rails in the sections prior to the output stage. This voltage "boost" allows the musical signal to exploit the full capability of the output voltage rails. Extending the musical signal swing closer to the output rails maximises the performance of the output circuitry design itself. The result is improved dynamics, lower distortion, and a fierce grip of the speaker.

Substantial Foundation

Abundant power is required for realistic sound quality and is a cornerstone of Dan D’Agostino Master Audio Systems’ amplifier design. The Progression Stereo continues this practice. A graceful anodised Aluminium chassis houses a 2,000 VA power supply transformer coupled to nearly 100,000 microfarads of power supply storage capacitance. Paired to this foundation is a fully complementary driver stage, and output circuitry outfitted with 48 power transistors - 24 each for the left and right channels generating an imposing output. Initially used in the Relentless Mono, the output power device provides the foundation for an upgraded output stage. This transistor extends high frequency response, increases power handling 50%, and features tighter tolerance gain matching between complementary NPN/PNP pairs. 

A wider safe operating area and superior gain linearity provides greater thermal stability throughout the amplifiers’ power delivery. Coupling the new output device to the high efficiency heat sink design affords an increase in operating bias. Higher operating bias lowers crossover distortion improving instrument timbre and tonal reproduction. The Progression Stereo delivers 350 Watts into 8 Ohms and delivers 700 Watts into 4 Ohms, and properly doubles its output again into 2 Ohms, with a 1,400 Watt power output. The essence of live music, dynamic contrasts, are faithfully reproduced with leading edge transients spectacularly depicted.

Elegantly Powerful

Drawn directly from the Relentless Mono Amplifier, each heatsink is milled from a single, 48.5-pound (22-kilogram) aluminium billet slab. This highly efficient elliptical form dramatically improves the cooling ability of the design and assures that the Progression S350 Stereo Amplifier runs safely and reliably even when delivering its full-rated power. Standard finishes include silver and black with custom painted finishes available on request.

Combining innovative circuitry and significant power, the Progression S350 Stereo amplifier provides loudspeakers the control element they need to achieve their full design expression.

Momentum S250 MxV Stereo Amplifier
Scaling New Heights

The Momentum S250 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 recognise that MxV or Mass times Velocity is the equation for Momentum.

Advances 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 re-invisioned 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 S250 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. Energising 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 S250 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 S250 MxV are among the fastest available. Using 26 on the Momentum S250 MxV amplifiers they run at a blistering 69 MHz, permitting the Momentum S250 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 S250 MxV amplifiers. As with all D'Agostino models, the Momentum S250 MxV amplifiers feature discrete, direct-coupled balanced circuitry, the most accurate circuit platform possible.

Big Power

Defying its compact size, the Momentum S250 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 100,000μF capacitor bank resulting in 250/500/1,000W of power output into 8/4/2Ω speaker loads for the Momentum S250 MxV The Momentum S250 MxV amplifiers are capable of driving any loudspeaker to its fullest potential.

Each Unit is Crafted with Scrupulous Attention to Detail.

The new Momentum S250 stereo amplifier receives a power upgrade, now delivering 250 Watts/channel into 8 Ohms. This is up from the original 200 Watt/channel specification. A 20% increase in transformer size, up to 1,800VA, provides the engine for this output power increase. Connected to this larger power source is a new output stage design that includes a number of major enhancements.

The driver section underwent a major revision and now features a fully complementary signal path with individual transistors employed for the positive and negative halves of the musical signal. Current drive is nearly doubled which feeds a new output stage with an open loop gain increased by the same factor of two. The sound is more spacious, delicate, and dynamic.

The Ability to Strive for More

The Momentum S250 employs the same chassis as the original with a small aesthetic design change to the copper feature on the faceplate sides. Additionally, the meter now displays a scale appropriate for the greater power output. If desired, a Momentum S250 Stereo Amplifier can be upgraded to a Momentum M400 Mono Amplifier when a system is ready to elevate to another performance level.

The distinctive power meter from the monoblock makes an encore appearance in the stereo amplifier, with a separate indicator needle for each channel. Like the mono amplifier, the stereo amplifier is hand-built and individually tested in D'Agostino's Arizona facility.

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 S250 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 S250 MxV stereo-block 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 S250 MxV employs the same chassis as previous Momentum amplifiers. All generations of Momentum stereo amplifiers can be upgraded to the Momentum S250 MxV performance level. All electrical enhancements are included in the upgrade while the original metalwork is retained. Original Momentum amplifiers receive a new 250 Watt meter plate reflecting the power output increase included in the upgrade. Momentum S250 units already have this power increase and meter.

S350 Stereo Amplifier

S250 MxV Stereo Amplifier