The Relentless Preamplifier
The new Relentless Preamplifier is the ultimate in preamplifier design. The preamplifier plays a critical role in musical playback; the point in the reproduction stage when the music signal is particularly susceptible to compromise through noise and distortion. The use of three separate chassis in the design of the Relentless Preamplifier—a dedicated audio chassis for each channel separated by a power supply/control section—addresses these challenges and brings other benefits as well.
Power Supply
Positioned between the two audio channels, the power supply makes use of extensive electrical and magnetic shielding to keep radiated interference out of critical preamplifier circuits. Internal line conditioning circuitry filters RF noise on the AC power and compensates for asymmetric power waveforms and DC on the mains. Power for the preamplifier stages comes from two 150 VA toroidal transformers – one dedicated to the analog circuitry and one for the digital and control circuitry. These transformers drive an 8-amp bridge rectifier and 26,400 microfarads of filter capacitance. The two regulators for the analog stages are scaled-down versions of those used in 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 Preamplifier has nearly as much power supply capability as many power amplifiers.
Expanding Horizons
The genesis of each mono preamplifier's input stage emerged from an innovative circuit design experiment, previously unexplored in any D’Agostino preamplifier. This experiment's incorporation into the Momentum Preamplifier and its subsequent success paved the way for the Momentum HD Preamplifier. Building on this momentum, the concept reached its zenith with the initiation of the Relentless Preamplifier project. At the heart of its audio circuitry, the Relentless Preamplifier introduces a novel discrete differential FET input stage, capable of handling an impressive 30-volt input signal. With its input impedance exceeding 1 MOhm, it stands resilient against any source-related electrical disturbances. To combat the potential performance and sound quality degradation due to component heating, a specially designed circuit ensures consistent bias, thus maintaining impeccable performance through prolonged listening sessions. Exclusively featuring balanced XLR inputs, the Relentless Preamplifier architecture is engineered to discard common-mode input noise across an extensive bandwidth. The amplification process is uniquely conducted in the current domain, utilizing proprietary multiple-output current mirrors that exhibit nearly 30-fold improvement in linearity over conventional designs. This precision is further enhanced by the employment of four-layer circuit boards, which significantly mitigate distortion and signal propagation issues, setting a new standard beyond the typical two-layer boards. The design meticulously segregates analog and digital circuit components, including their respective ground planes. Digital controls interface with analog circuits through optical coupling, ensuring pristine signal integrity. Additionally, signal switching is managed by hermetically sealed relays with gold-plated contacts, optimizing signal purity. Eschewing negative feedback entirely, the core philosophy of D’Agostino's circuitry champions a signal path that is both fully complementary and balanced from the input stage right through to the output, culminating in a frequency response that remains flat up to 120 kHz. The outcome is a signal that is not only rich in musical detail and dynamic range but also faithfully delivered through the balanced outputs, embodying the pinnacle of audio excellence.
Separate but Linked
Arguably, the most striking element of the Relentless Preamplifier is the pair of volume controls fronting the two audio chassis. Volume control circuits are often overlooked, if not actively minimized, in preamplifier designs. This is not the case in the Relentless Preamplifier. Each volume control is constructed using 14 separate metal components ensuring the smoothest response and control of the military-grade, high-linearity solid-state switches and discrete precision resistors employed in the volume circuit. The bandwidth and transient response of the Relentless Preamplifier is completely unaffected by the volume setting. As a result, high frequencies sound especially smooth and extended, and music emerges from “jet black” silence.
The volume settings are displayed via the elegant swiss watch inspired volume wands or can be displayed numerically, from 0 to 99.
Two Preamplifiers 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 may be two analog sources or when equipped with the optional digital streaming module, one digital source and one analog source. In a one zone system, either volume control will adjust volume in the main room or Zone 1. If two zone operation is desired, the upper volume control manages the Zone 1 volume and the lower volume control adjusts the Zone 2 volume.
Advanced Remote Control Technology
Bluetooth 5.0 technology extends the usable range of the remote control and eliminates the line-of-sight issues that plague conventional infrared designs.
Integration Features
The Relentless Preamplifier’s primary focus is centered around ultimate stereo playback but it fits nicely in a home theater system. Input Three can be configured for Theater Bypass. In this mode, the Relentless Preamplifier’s volume control is bypassed and volume control for the main loudspeakers is now controlled by the connected surround-sound processor. RS-232 and 12 Volt triggers facilitate integration into advanced home control systems. Additional DC power outputs for future products as well as two programming ports offers easy growth and performance options in the future.
Optional Digital Streaming Module (DSM)
The Relentless Preamplifier is the first D’Agostino preamplifier to offer an optional DSM. This digital enhancement adds connectivity for legacy sources, USB functionality, and premier streaming capability. Field upgradeable, the DSM adds SPDIF coaxial, Optical, USB-A, and RJ-45 and Wi-Fi network inputs. For latency free playback of high-resolution network content, 10/100/1000 Gigabit Ethernet is supported.
Customized apps for iOS devices provide easy control of music collections, streaming content, and unit control. Subscription streaming services Tidal, Qobuz, and Spotify are native within the app. With appropriately encoded music files, MQA decoding is standard. Additionally, Roon Music management is also available as an alternative music management program.
Completely isolated from the analog circuitry, the DSM is housed in the power supply/control chassis. Requiring three separate circuit boards the core element is a pair of DACs configured in differential mode with each one configured to handle the positive and negative signals for each channel. Capable of handling today’s highest resolution sources, PCM signals up to 32 bit/384 KHz and DSD signals up to DSD256 (11.2MHz) are decoded natively. Often overlooked or downplayed, the analog section of a DAC significantly impacts the final sonic performance of digital music. Internal balanced connections carry the final analog signal to the connecting feet and onward to each audio chassis. From here, the analog music signal takes advantage of the entire power and analog circuitry within the three chassis of the Relentless Preamplifier.
Coupling innovative circuitry, distinctive materials, and artisan manufacturing excellence in a sophisticated architecture, the Relentless Preamplifier is the perfect centerpiece for the ultimate music system.
