Dan D'Agostino Momentum C2 Pre-Amplifier

In the design of the Momentum C2, a dedicated audio chassis and separate power supply are utilized to achieve optimal mechanical and electrical isolation. These two chassis are interconnected using specialized electro-mechanical connectors integrated within each unit. Thirty-pin interlocking connectors, gold plated and capable of handling 20 amps, replace conventional wiring typically utilized in similar applications, effectively reducing the risk of potential anomalies. This distinctive configuration guarantees complete isolation of the audio signal, both physically and electrically, from the power supply components. Furthermore, this physical segregation creates additional space for the optimization of both power and audio circuitry.

New for the Momentum C2 Preamplifier is enhanced digital capability. An LED display provides operational status and when equipped with the optional digital streaming module (DSM) metadata from digital music sources. A new two-way remote control featuring Bluetooth technology also provides this information in the palm of your hand. 

Unrivalled Audio Circuitry

This circuitry represents an evolution from the utilization of JFET transistors in D’Agostino preamplifiers, which debuted in the Momentum HD Preamplifier and has been further perfected in the Momentum C2 Preamplifier. The innovative Momentum C2 topology employs a distinct configuration of four JFET transistors arranged in a complementary, push-pull design, significantly enhancing input impedance. This enhancement serves as a foundation for the entire preamplifier topology, effectively isolating it from the prevalent extraneous noise in audio systems. With an input impedance surpassing 1 megaohm, the JFETs themselves stand as the least noisy devices available. When integrated into the new C2 circuit arrangement, they effectively reduce the overall noise floor in this crucial stage.

The audio circuit topology starts with a completely unique, new discrete dual-complementary differential JFET input stage featuring a voltage input signal capability of an extraordinary 30 volts. The Momentum C2 Preamplifier’s front end is immune to source-related electrical issues.  In normal operation, component heating can lead to performance and sonic degradation. Developed specifically for the Momentum C2 Preamplifier, a unique circuit maintains a stable bias so that temperature-related anomalies are offset, thus preserving performance during extended listening. 

Utilizing no negative feedback anywhere, core D’Agostino circuit concepts include a signal path that is fully complementary, direct coupled, and balanced from input to output, achieving a frequency response flat to 120 kHz.

All signal gain is realized in the current domain using proprietary multiple-output current mirrors with nearly 30 times the linearity of other designs. Executed with four-layer circuit boards for superior signal quality, the use of four-layer boards dramatically reduces distortion and propagation losses as compared to the more commonplace, two-layer boards.

Analog and digital circuit elements are isolated, including ground planes, from each other. Where necessary, digital control signals are optically coupled to analog circuits. The signal-switching relays are hermetically sealed and use gold-plated contacts for maximum signal integrity. 

In many preamplifier designs, volume control circuits are either overlooked or intentionally downplayed. However, this is not the case with the Momentum C2 Preamplifier. Each volume control is meticulously crafted using 14 distinct components, ensuring the smoothest response and precise control over the military-grade, high-linearity solid-state switches and discrete precision resistors incorporated in the volume circuit. Consequently, the bandwidth and transient response of the Momentum C2 Preamplifier remain unaffected by the volume setting. Volume levels are elegantly displayed through the Swiss-watch-inspired volume wand, or can be shown numerically, ranging from 0 to 99.

The seldom-seen tone control circuitry within the Momentum C2 Preamplifier remains entirely transparent in its operation, ensuring zero impact on the signal path when inactive. Concealed behind a discreet door on the front panel, a headphone jack featuring independent amplifier circuitry is also provided for added versatility.

Unmatched Power Supply

Housed in a separate chassis to maximize isolation, power delivery duties are shared by individual transformers dedicated to the analog and digital circuitry. Utilizing a unique winding technology, initially employed in the Momentum M400 amplifier, this design delivers increased power output within the same footprint. Internal circuitry addresses RF noise from the AC power line, compensating for asymmetric power waveforms and DC on the mains. 

Capitalizing on the augmented power supply capability, the output stages operate at a 36% higher voltage, offering enhanced dynamics at both micro and macro levels. Also, present in the power supply chassis is an LCD display showing unit status, functions, and when equipped with the optional digital streaming module, metadata from equipped digital music sources.

Digital Streaming Module (DSM)

The Momentum C2 Preamplifier offers an optional DSM that adds connectivity for legacy sources, USB functionality, and premier streaming capability. Field upgradeable, the DSM adds SPDIF coaxial, optical, USB-B, RJ45, and Wi-Fi network inputs. For latency-free playback of high-resolution network content, 10/100/1000 Gigabit Ethernet is supported.

Tailored iOS apps facilitate effortless control of music collections, streaming content, and unit functions. Native integration with subscription streaming services like Tidal, Qobuz, and Spotify is supported within the app, with additional compatibility for Tidal Connect. Furthermore, with appropriately encoded files, standard MQA decoding is enabled. For users preferring alternative music management, Roon Ready certification will also be available.

Capable of handling today’s highest resolution sources, the DSM natively decodes PCM signals up to 32 bit/384 kHz and DSD signals up to DSD256 (11.2 MHz). 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 directly to the input circuitry. From here, the analog music signal takes advantage of the entire power and analog circuitry within the Momentum C2 Preamplifier.

Advanced Control

Housed in precision-machined aluminum and Delrin, the Momentum C2 Preamplifier’s remote control is a Bluetooth-enabled device, rechargeable via USB, boasting an ergonomic design and featuring an LCD screen. Offering bi-directional functionality, the remote mirrors the information on the Momentum C2 Preamplifier’s front panel onto its own display screen, including input, volume, and balance settings. Additionally, with the optional DSM installed, song metadata is also shown on the display.