Did Krell high-end audio components ever look this good? Dan D’Agostino has always demonstrated a rather keen sense of industrial design and very intense focus on engineering. It’s hard not to be seduced by the look and feel of his components — but make no mistake — he really knows how to build great sounding equipment that lasts forever.
Dan D’Agostino Master Audio Systems has unveiled the Momentum C4 Preamplifier, a significant advancement on its award-winning Momentum Preamplifier. The latest version expands on the well-received framework of the Momentum Preamplifier platform, as well as incorporating technical, features, and sonic attributes inspired by the flagship Relentless Preamplifier.
The designation “C4” corresponds to the new Complementary Four circuit topology that makes up the unique input stage circuitry employed in the front end of the preamplifier.
In the design of the Momentum C4 Preamplifier, 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 C4 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.
Audio Circuitry Highlights
This circuitry represents an evolution from the utilization of JFET transistors in D’Agostino preamplifiers, which debuted in the Momentum HD Preamplifier and was further perfected in the Momentum C4 Preamplifier. The innovative Momentum C4 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 C4 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 of input signal the Momentum C4 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 C4 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.
“The Momentum C4 Preamplifier represents a significant leap forward for our Momentum platform. Drawing insights from our pioneering work on the Relentless Preamplifier, the Momentum C4 topology achieves a level of transparency that is unparalleled in preamplification but for its bigger brother,” stated Dan D’Agostino, Co-Founder and Chief Engineer.
In many preamplifier designs, volume control circuits are either overlooked or intentionally downplayed. However, this is not the case with the Momentum C4 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 C4 Preamplifier remain unaffected by the volume setting. Volume levels are elegantly displayed through the Swiss watch-inspired volume wands or can be shown numerically, ranging from 0 to 99.
The seldom-seen tone control circuitry within the Momentum C4 Preamplifier remains entirely transparent in its operation, ensuring zero impact on the signal path when inactive. Concealed behind a discrete door on the front panel, a headphone jack featuring independent amplifier circuitry is also provided for added versatility.
Power Supply Highlights
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 increases power output within the same footprint. Internal circuitry addresses RF noise from the AC powerline, 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.
Advanced Control
Housed in precision-machined aluminum and Delrin, the Momentum C4 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 C4 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.
Optional Digital Streaming Module (DSM)
The Momentum C4 Preamplifier marks a milestone as the first D’Agostino Momentum preamplifier to offer an optional Digital Streaming Module. This digital enhancement expands connectivity options for digital legacy sources and introduces premier streaming capabilities. Easily upgradeable in the field, the DSM incorporates SPDIF coaxial, Optical, USB-B, RJ-45, and Wi-Fi network inputs. To ensure seamless playback of high-resolution network content without latency, it supports 10/100/1000 Gigabit Ethernet.
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 the highest resolution sources available today, the Momentum C4 decodes PCM signals up to 32 bit/384 KHz and DSD signals up to DSD256 (11.2MHz) natively. Recognizing the crucial role of the analog section in digital music performance, internal balanced connections ensure optimal signal transfer to the C4 circuitry stage, leveraging the full potential of the preamplifier’s power and analog circuitry across its two chassis.
Price & Availability
Every Momentum C4 Preamplifier is hand-built and individually tested in D’Agostino’s Arizona factory by their technicians and craftsmen. The Momentum C4 is $50,000 for the base model. The optional Digital Streaming Module is $10,000 and will begin shipping in July, 2024 in silver or black finishes.
For more information: dandagostino.com
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