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Dan D'Agostino Master Audio Systems Relentless Preamplifier

Fundamentally Better

By Michael Fremer

The Dan D'Agostino Master Audio Systems Relentless Preamplifier is a distinctive audio component, characterized by its multi-chassis design and advanced engineering. The reviewer initially inquired about the umbilical connections between the chassis, only to learn that the three units link directly via integrated multi-pin plugs and jacks on the chassis top and bottom plates, with these connections not carrying audio signals.

The reviewer's prior experience with the Relentless preamp at Innovative Audio in New York City, paired with Wilson Audio Specialties Chronosonic XVX speakers and driven by smaller D'Agostino Relentless 800 amps, left a strong impression. This setup, which included sources from dCS and TechDAS/SAT, provided an "unforgettable sonic experience" with sound that was "fundamentally better," more transparent, and featured a more distinct and insistent soundstage with effortlessly placed images.

Following this positive encounter, Michael Fremer received an invitation from Bill McKiegan of D'Agostino Master Audio Systems to review the Relentless preamp at home. This review process was initiated through a personal connection rather than a standard procurement route.

The Three-Box Monster

The Relentless Preamplifier is presented as a "three-box monster," comprising two sturdy chassis, each dedicated to a signal-carrying channel, sandwiching a third chassis that houses the control system and power supply. This configuration contributes to its substantial presence and weight.

Aesthetics: The design features two large, backlit "one-hand" clock-like volume controls set into the chassis fascia. These controls are described as "bold and dramatic eye candy," though the reviewer notes that the product's visual appeal might not be universally appreciated. A waiting list reportedly exists for the unit, indicating demand beyond its aesthetic qualities.

Overbuilt Power Supply: To prevent radiated interference from reaching sensitive signal paths, the power supply employs extensive electrical and magnetic shielding. The internal line-conditioning circuitry filters RF noise from the incoming AC power and compensates for asymmetrical power waveforms and DC infiltration. The power supply utilizes two large 150VA toroidal transformers—one for analog and one for digital/control circuitry—driving an 8-amp bridge rectifier and 26,400 microfarads of filter capacitance. It features separate digital and analog regulators, with the latter being pared-down versions from the Relentless monoblock amplifier. D'Agostino claims the power supply has nearly as much capability as many power amplifiers and that the robust construction and filtering eliminate the need for external power conditioning or special footers.

FET Sounds / Signal Handling: Signal handling begins with a "highly evolved" discrete, differential FET input stage, capable of managing a 30-volt input signal. This design is rooted in a "novel" circuit experiment that also influenced the Momentum phonostage and preamp input stages. With an input impedance exceeding 1 megaohm, it is said to be unaffected by source-related electrical disturbances. A special circuit maintains consistent bias to prevent sound quality degradation due to heat buildup. The unit employs "proprietary multiple-output current mirrors" for "current-domain amplification," which reportedly offers a nearly 30-fold improvement in linearity over conventional designs.

Internal Construction: The internal layout features distortion-reducing four-layer circuit boards. The design meticulously segregates analog and digital circuit components, including their ground planes. Analog circuit signal integrity is maintained through digital control optical coupling. Hermetically sealed relays with gold-plated contacts contribute to signal purity. The zero negative feedback design boasts a claimed flat frequency response up to 120kHz.

Volume Control: The Relentless' volume control is constructed from 14 separate metal components, providing a smooth and precise physical response. It controls military-grade, high-linearity solid-state switches and discrete precision resistors. Both bandwidth and transient response are stated to remain unaffected by the volume setting, with music emerging from "jet-black" silence.

Basic Facilities: The power-supply chassis fascia is equipped with two sets of five illuminated buttons, separated by a circular numerical volume setting display. Buttons are provided for standby/power on, mute, polarity, and Zone 1/Zone 2 independent operation. The display's right side features five additional buttons. The meters change color or blink based on the setting. D'Agostino prioritized design simplicity for the front panel.

Remote Control: A circular Bluetooth 5.0 bi-directional touchpad remote is included, eliminating the need for IR line-of-sight. It duplicates all front-panel operations except for Theater Bypass mode and offers additional controls. The tactile feel of the remote's volume control knob is compared to an old-school analog FM tuner station selector.

Rear Panel Connectivity: The signal chassis rear panels feature five XLR inputs and three XLR output pairs: one for Zone 1 and one for Zone 2. RCA/XLR adapters can be used for unbalanced sources. The power-supply rear chassis includes an IEC AC jack/main power switch, a Bluetooth antenna jack, a pair of 12V trigger outputs, an RS-232 control connector, and openings for DSM (Digital Streaming Module) and preamplifier programming access, including a large hatch for the optional Digital Streaming Module.

Setup and Use

The setup process is described as exceptionally easy, matched only by the tactile pleasure of rotating the large, smoothly turning knurled copper peripheral volume adjustment rings. In single-zone operation, the two volume meters are synchronized.

Dual-zone operation allows for playing the same source in two locations or different sources in each zone. In this mode, the volume meters become unsynced, with the upper meter controlling Zone 1 and the lower controlling Zone 2. The reviewer notes that a fixed-gain recording output was not present as delivered but was told it could be easily modified via code.

Listening Impressions and Comparison

The reviewer compares the Relentless to their reference battery-powered darTzeel NHB-18NS ($65,000), noting the darTzeel's strengths in "musicality" and freedom from artifacts like grain and "etch," but also its relatively high noise floor.

The first serious listening session involved the direct-to-disc recording of Bruckner's 7th Symphony with Bernard Haitink conducting the Berlin Philharmonic (BPHR 200271-2LP). The recording utilized a specific microphone array (Josephson C700S stereo-mic and C722 mics) and Siemens V72/V76 preamps and mixer.

The reviewer states unequivocally that the Relentless preamp "fundamentally and totally improved in every conceivable way" the sound of this record and the understanding of the performance. It presented the orchestra and the Berlin Philharmonic space more convincingly than any previous experience with the recording. The reviewer emphasizes that descriptions of "better bass" or "improved bottom end" are insufficient, as "everything was so fundamentally better." The first movement's opening is noted for its unusually long, sustained tone.

Specifications & Pricing

Specification Details
Frequency response 0.1Hz–120kHz
Signal-to-Noise Ratio -105dB (unweighted) / -100dB (weighted)
Gain +6/+10dB selectable
Finish Silver or black; custom finishes available
THD <0.006%, 20Hz–20kHz
Inputs Five pair balanced via XLR connectors
Outputs Two pair balanced via XLR (Zone 1), one pair balanced via XLR (Zone 2)
Dimensions (preamp) 17" x 3.9" x 17"
Dimensions (power supply/base) 17" x 3.9" x 17"
Weight 132 lbs. total
Price $151,000 ($170,950 with Digital Streaming Module)

Manufacturer Information

D'AGOSTINO MASTER AUDIO SYSTEMS, LLC
5855 E. Surrey Drive
Cave Creek, AZ 85331
(480) 575-3069
dandagostino.com

Associated Equipment (for this review)

The reviewer also notes that D'Agostino is potentially developing a next-generation phono preamp, based on the inclusion of power-supply DC outputs for future products.

The reviewer concludes that D'Agostino prioritizes simplicity in operational features, avoiding excessive "tchotchkes" like input naming. The remote offers balance and +8/+14dB output gain options. A "dark mode" can extinguish all front-panel and remote-control illumination until the volume is adjusted.

The setup ease is highlighted, along with the tactile pleasure of the volume control. Dual-zone operation is explained, and the reviewer mentions that the unit's design philosophy suggests that users who can afford such equipment likely prefer straightforward operation over complex interfaces. The touchscreen remote's operation requires some initial orientation.

In comparison to the darTzeel NHB-18NS, the Relentless is described as fundamentally better in every conceivable way, offering improved musicality and freedom from artifacts. The reviewer emphasizes that the performance uplift goes beyond typical descriptions of bass or frequency response, representing a complete enhancement of the listening experience.

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