The Relentless preamplifier.

The new Relentless preamp is the latest in preamp design. The preamplifier plays a critical role in music reproduction; it is the point in the playback stage where the musical signal is especially susceptible to noise and distortion. The use of three separate chassis in the Relentless preamplifier design - a dedicated audio chassis for each channel, separated by a power/control section - addresses these challenges and brings other benefits as well.

Power supply.

Located between the two audio channels, the power supply uses extensive electrical and magnetic shielding to keep radiated interference out of critical preamplifier circuitry. Internal line conditioning circuitry filters out RF noise in the AC power and compensates for asymmetrical waveforms of the power and DC in the network. The preamplification stages are powered by two 150 VA toroidal transformers, one dedicated to the analog circuits and the other to the digital and control circuits. These transformers drive an 8-amp bridge rectifier with 26,400 microfarads of filtering capacity. The two regulators on the analog stages are scaled-down versions of those used on the Relentless Mono amplifier. The separate digital regulator is a monolithic platform with thermal and current limiting protection in the unlikely event of a fault. The Relentless preamp has almost as much drive capacity as many power amps.

room to breathe

The input stage of each mono preamplifier is the result of a circuit design experiment that had not been used in any previous D'Agostino preamplifier. As part of the development, a version was tested on the existing Momentum preamplifier. The overwhelmingly positive results led directly to the release of the Momentum HD preamplifier. From there, the ultimate expression of this idea was developed, and the Relentless Preamplifier was underway.

The audio circuit topology begins with a new discrete differential FET input stage that features a voltage input signal capability of an impressive 30 volts. With an input impedance of over 1 MOhm, the Relentless preamplifier front end is immune to source-related electrical problems. In normal operation, heating components can cause performance and sound degradation. Developed specifically for the Relentless Preamplifier, a unique circuit maintains a stable bias so that temperature-related anomalies are compensated for, thus preserving performance during extended listening.

Featuring only balanced XLR inputs, the Relentless preamplifier topology rejects common-mode input noise over an unusually wide bandwidth. All signal gain is done in the current domain using patented multi-output current mirrors with linearity nearly 30 times higher than other designs. Made with four-layer circuit boards for superior signal quality. The use of four-layer boards drastically reduces distortion and propagation levels compared to the more common two-layer boards.

Analog and digital circuit elements are isolated, including ground planes, from one another. When required, digital control signals are optically coupled to analog circuitry. Signal switching relays are hermetically sealed and use gold plated contacts for maximum signal integrity.

Using no negative feedback anywhere, the basics of D'Agostino circuitry include a fully complementary and balanced signal path from input to output, achieving a flat frequency response down to 120kHz. The overall result is a musically dense and dynamically rich signal presented to the balanced outputs.

Separate but united.

Arguably the most striking element of the Relentless preamp is the pair of volume controls that sit in front of the two audio chassis. Volume control circuitry is often overlooked, if not actively minimized, in preamplifier designs. This is not the case with the Relentless Preamplifier. Each volume control is constructed of 14 separate metal components ensuring the smoothest response and control from the high-linearity, military-grade solid-state switches and precision discrete resistors employed in the volume circuitry. The bandwidth and transient response of the Relentless preamplifier are completely unaffected by the volume setting. As a result, high frequencies sound especially smooth and extended,

Volume settings are displayed via elegant Swiss watch-inspired volume rods or can be displayed numerically, from 0 to 99.

Two preamps in one.

The Relentless Preamplifier is a two source/two zone preamplifier. This means that the Relentless Preamplifier can simultaneously control the switching and volume of two sources in two separate rooms or zones. Listening sources can be two analog sources or, when equipped with the optional digital transmission module, one digital source and one analog source. In a one-zone system, either volume control will adjust the volume in the main room or zone 1. If two-zone operation is desired, the top volume control manages the Zone 1 volume and the bottom control controls the Zone 1 volume. lower volume adjusts the volume of Zone 2.

The status of the preamp in hand.

The Relentless preamplifier remote control, made of aluminum and copper, has a comfortable design that is operated via a touch panel. Control buttons are kept to a minimum and most operations are performed via a touch panel. Bluetooth 5.0 technology extends the useful range of the remote and eliminates line-of-sight issues that plague conventional infrared designs. New to the Relentless preamplifier is the 2-way remote control functionality. All adjustments made on the front panel of the Relentless preamp are reflected on the remote's display, including input, volume and balance selections.

Integration features.

The main focus of the Relentless preamplifier is on ultimate stereo reproduction, but it is perfectly suited to a home theater system. Input three can be configured for cinema bypass. In this mode, the volume control of the Relentless preamp is bypassed and the volume control of the main speakers becomes controlled by the connected surround processor. RS-232 and 12-volt triggers make it easy to integrate into advanced home control systems. Additional DC power outlets for future products, as well as two programming ports, facilitate future growth and performance options.

Optional Digital Transmission Module (DSM).

The Relentless preamp is the first D'Agostino preamp to offer an optional DSM. This digital upgrade adds connectivity for legacy sources, USB functionality, and world-class streaming capability. Field upgradeable, the DSM adds coaxial, optical, USB-A and RJ-45 SPDIF network inputs and Wi-Fi. For latency-free playback of high-resolution network content, it supports 10/100/1000 Gigabit Ethernet.

Custom apps for iOS devices make it easy to control music collections, streaming content, and drive control. Tidal, Qobuz, and Spotify subscription streaming services are native within the app. With music files properly encoded, MQA decoding is standard. In addition, Roon music management is also available as an alternative music management program.

Completely isolated from analog circuitry, the DSM is housed in the power/control chassis. Requiring three separate circuit boards, the core element is a pair of DACs configured in differential mode with each configured to handle the positive and negative signals of each channel. Capable of handling today's highest resolution sources, PCM signals up to 32bit/384KHz and DSD signals up to DSD256 (11.2MHz) are natively decoded. Often overlooked or downplayed, the analog section of a DAC significantly influences the final sonic performance of digital music. Balanced internal connections carry the final analog signal to the jack stands and to each audio chassis. From now on,

Combining innovative circuitry, distinctive materials, and craftsmanship excellence in a sophisticated architecture, the Relentless preamp is the perfect centerpiece for the ultimate music system.

Specifications:

Frequency response 0.1 Hz to 120 kHz, +/- 0.0 dB.

Signal to noise ratio -105 dB, unweighted / -100 dB, weighted.

Gain + 8/+14dB selectable.

Silver or black finish with custom finishes available upon request.

Total Harmonic Distortion <.006%, 20Hz to 20kHz.

Inputs 5 pr - Balanced via XLR connectors.

Outputs 2 pr Balanced via XLR connector for Zone 1, 1 pr Balanced via XLR.

Dimensions 17 x 1.75 x 17 in / 43.2 x 34.9 x 43.2 cm.

Weight 132lbs / 60kg.

Manual Relentless_Preamp_Manual.pdf (9.82 MB).

Dimensions (preamp) 17 x 3.9 x 17 in / 43.2 x 9.9 x 43.2 cm.

Dimensions (Power Supply/Base) 17 x 3.9 x 17 in / 43.2 x 9.9 x 43.2 cm.

Analog inputs 5 balanced XLR stereo pairs.

Digital inputs (with DAC module installed) 1 USB type A, 1 optical, 1 SPDIF, 1 coaxial, Ethernet RJ45, 1 WiFI.

RS-232 control.