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Overview
The 404 Reference integrated amplifier
Following the runaway success of The Moonriver Model 404 (Standard), we decided to move a step further by improving on the already excellent design platform of the Standard 404 model. The Moonriver Model 404 Reference achieves even better performance over the Standard Model, while retaining a sensible price point.
Just like the Standard Model 404, the 404 Reference amplifier will extract hidden elements, and render textures from within any audio format; but with the capability to drive any speaker on the market – despite its moderate power. Only the source, speakers and room will set the performance limit. Its culture will suit all music, as the Model 404 is by design, set to define the faintest nuances of which tonal integrity is composed.
The power supply section has been improved to the maximum. The 404 standard uses a total of 57000uf capacitance. The 404 Reference lifts the capacitance to a spectacular 107000uf of which 21000 of them are reserved for the preamp only. This enormous increment expands the driving behaviour; the dynamic character; digs out more detail; low level information; a deeper and more articulate soundtstage; space between instruments is vast, while the bass has greater authority and is more confident than ever before.
The texture of each individual instrument is exposed exponentially in comparison with the Standard version. A fully discrete preamp section serves to provide acute dynamic awareness, while a high output stage that is custom-optimised for bandwidth and distortion, gives neutral character and transient fidelity. A sophisticated selection of components fuses the design against tonal traits, therefore preserving naturalness throughout the shortest feasible signal path.
Furthermore, an integrated phono stage, USB DAC, (two) preamp outputs and a tape monitor loop expand functionality to form an ideally flexible integrated amplifier.
Modular Architecture
Moonriver 404 Reference amplifier is modular like its brother; it can accommodate an MM or MM/MC phono stage and a USB asynchronous DAC. Fitting these modules is simple, and can take place at any time, on or after purchase. The USB DAC may also be upgraded with a newer version to meet future needs and technologies.
Balance Control
You may find this feature to be vanishingly scarce in audiophile products as a result of today’s ‘minimalist’ design mentality and the various myths accompanying it. However, balance control addresses a common problem: speakers that are positioned in asymmetry, in a non-balanced room environment. It therefore provides the simplest tweak towards achieving a proper soundstage.
Living rooms and house furniture are meant to serve everyday life and may not be positioned in an ideal listening spot, evenly distanced from each speaker to form an equilateral triangle. It is also not uncommon for one speaker to have to be placed nearer room boundaries than the other, having various frequencies boosted in a more or less predictable pattern. More often than not, balance control is incredibly useful as it drastically helps overcome volume level unevenness and in some cases, even reclaiming the stereo effect and the resulting focused sound stage.
It is to be expected, the way the balance control is implemented on the Moonriver 404 Reference amplifier – in parallel, will not degrade or affect the signal in any way that is determinable.
Discovering the layout
Model 404 Reference, like the standard model, incorporates no less than 5 separate power supplies, each featuring overload protection. The power amplifier specifically runs on a dual mono configuration, beginning from separate windings on the toroidal transformer.
WBT nextgenTM speaker terminals ensure the massive flow of current from the amplifier’s output stage, is able to drive even “difficult to drive” speakers.
Signal switches are implemented via relays, while volume attenuation is trusted on the legendary blue ALPS pot.
A soft start circuit based on a 30A relay ensures that even the on/off switch is thought out to work with virtually no burden or wear for decades.
The 404 Reference chassis reduces unwanted resonant vibrations even further with absorbent materials, and better integral mechanical support.
Components are carefully selected for both suitability and reliability. We make no use of surface-mount in analog circuits, despite the fact that through-hole production costs more, and requires advanced space management & layout strategies.
Each element utilised has to be of proven stability and sustained higher performance – proficient implementation provided, before making it into our analog paths.
As for the sound, we are not to say whether Model 404 Reference is virtually transparent or inherently forgiving. Voicing it to appreciate the playlist and respect the user at all times has been the sum of all of our effort; a sincere effort to achieve effortlessness.
Optional Phono Stage
Model 404 Reference comes with two options in the phono stage department; one is MM only and the other is MM/MC selectable. Both follow the exact quality principles that Model 404 Reference is built on. Quality components and massive power supplies are also employed here, to efficiently accommodate very low noise, high performance op-amps.
The gain in the MM/MC phono can be adjusted, simply by changing the dip switches position. The MC input load can be set also, by replacing the original 100 Ohm input resistor with a higher or lower value. No soldering is required.
Optional SPDIF DAC
The add-on dac module is based on the 9000 series ESS Sabre dac chip. The SPDIF supports PCM streams up to 192kHz/24bit due to the limitation of the SPDIF (coaxial) specifications. There are 3 separated power supplies with very low noise regulators, 2 for the ESS dac board and 1 for the analog circuit. The capacitor bank is massive and it uses 42000uF (in case of 404 Reference) from the power amplifier’s power supply.
Specially care has been given to the voicing of the analog output stage to match the dynamic and natural character of Moonriver sound. The result is an impressive sounding digital-to-analog converter which respects the timing, the space and the color of the music and unfolds the dynamic contrast – the definition of every musical event.
Optional USB DAC
What was desired for our USB DAC module was not to make an addition rather than an omission; instead we had to be confident of substantially raising the true value and functionality of Model 404.
The add-on USB dac module is also based on the 9000 series ESS Sabre dac chip with native DSD support. The USB dac supports PCM up to 384kHz/24bi and DSD up to 128. The USB input section is separated with discrete, very low drift clocks, XMOS input based chip with custom firmware. There are 5 separated power supplies with very low noise regulators, 2 for the USB board, 2 for the ESS dac board and 1 for the analog circuit. Specially care has been given to the voicing of the analog output stage to match the dynamic and natural character of Moonriver sound. The capacitor bank is massive and it uses 42000uF (in case of 404 Reference) from the power amplifier’s power supply.
A new USB DAC for the Moonriver 404 Standard and Reference will be announced shortly.
Specifications
Accessories
We currently do not have any accessories available for Moonriver Audio Reference 404 Integrated Amplifier.
