The 505 Hybrid Phono Stage

Full Review - The EAR.NET : Moonriver Audio 505 Hybrid MM/MC Phono Stage

The Moonriver Audio 505 phono stage meets all the needs of any demanding audiophile who loves vinyl records, both now and in the future. Designed with audiophiles, record collectors and vinyl freaks in mind, it boasts 4 inputs for all your turntables, tone-arms and cartridges. It also supports every possible adjustment on the fly with dedicated knobs and switches to ideally match your MC or MM cartridge.

The unique, adjustment feature of the Moonriver 505 hybrid phono stage allows on the fly listening tests with various adjustments without the need to switch off, remove the cover, switch on again and wait to warm it up.

The hybrid design combines the use of ICs and discrete solid-state circuits to form an ideal, high performance and ultra low noise circuit. While the IC op amps offer very low noise levels, a discrete circuit offers lifelike drive and dynamics which is impossible to get from IC op-amps.

As for the sonic signature of all Moonriver Audio products, we strive to balance the fine line between musicality & resolution. The soul of the music is in the midrange, this is where most of the emotion, the passion, the joie de vivre is contained.

On a technical level, its within the frequency band of 200 4,000Hz. Without a solid foundation underneath the midrange, the music sounds thin & brittle and often un-involving. If the brain perceives that the sound is artificial, then its difficult to be swept away by the message contained within the music.

Similarly, accurate timbre reproduction is essential. A New York Steinway does have noticeable sonic differences from a Hamburg Steinway, while a Guarneri violin sounds distinct from a Stradivarius. To capture all those nuances, the loudspeakers & electronics need to act in unison, neither obscuring, nor exaggerating detail.

The sound and the level of performance of the Moonriver 505 phono stage is hard to describe and it must be heard to be believed.

Design & User Interface

Moonriver had a very clear vision when conceiving the Model 505 hybrid phono stage: Classic design with a modern touch; high quality materials such as oversized aluminium knobs, solid walnut cheeks, sturdy chassis and an ergonomic user interface. There are no for show aesthetics here, no display with complicated serial menus and hidden functions, nor a single multi-function knob for minimalistic purposes. The heart of the Model 505 is pure and minimal, but the interface is user-oriented and easy to operate by anyone in seconds, with no need to resort to the user manual.

Features

Giving direct access to all necessary adjustments, the 505 includes 4 knobs and 5 switches for all the adjustments: 4 inputs, 12 gain settings (6 for MM and 6 for MC), 5 MM capacitance settings, 5 MC load settings, including a custom option, 3 MM load settings and EQ choice for RIAA, Decca or Columbia 78 rpm records. The 505 phono stage will handle the signal from your precious MC cartridge with unmatched performance and it will make your everyday MM cartridge sound like never before.

Power Supply

The Moonriver 505 hybrid phono stage contains 6 separated power supplies, including a massive 70000uf total capacitance and it is designed in dual mono operation. Each stage has its own power supply, including a linear discrete regulator circuit and a discrete noise rejection circuit.

Active Gain Stage

Using ultra low noise active gain stages, the Moonriver 505 delivers a maximum gain of 72dB (x4000 times) in the MC setting. The MM and MC settings use different input stages with different op amps specifically chosen for each case. All setting functions are performed with air sealed, extremely low impedance relays. Finally, a discrete, high current output circuit delivers lifelike dynamics on the output.

Microcontroller Operation with Save Memory Function

A microcontroller controls all functions and ensures an entirely silent operation. Every setting change is stored automatically for each of the 4 inputs. Every time you change the input, the last chosen settings are recalled automatically. For example, you can connect 4 MC cartridges or 4 MM cartridges or 2MC and 2 MM, or 3 MM and one MC, every combination is possible with different settings for every input.

De-emphasis EQ

The de-emphasis circuit is passive, the best possible approach for extreme flat frequency response without interference with the other stages. The EQ circuits involve 2 equalisation curves, a RIAA and a DECCA or COLUMBIA curve for 78rpm records. Both EQ circuits are formed using a minimalistic approach with very few, extremely low tolerance, audiophile quality components.

Layout highlights

The layout of the PCB is designed with 3 principles in mind: Isolation in-between noise sources and sensitive audio signal as the transformer and gain stages, a minimalistic approach with less components as possible in the signal and the shortest signal path possible. Moonriver 505 is using double shielding, one for the transformer and one for the active gain circuits. This approach eliminates the need for an external transformer and the disadvantages of it.

Components

The layout is mainly based on discrete, through hole components except the input for MM and MC stages with their impedance and capacitance adjustments which are using surface mount components to keep the signal path as short as possible. The components are carefully chosen in order to deliver the most possible open and transparent sound from input to output and to reveal the texture and the micro and macro dynamic content of each record. The Moonriver 505 hybrid phono stage reveals previously unheard details and qualities in your vinyl records, including micro-contrast and low level information that you may have not experienced otherwise.

Specifications 

Physical characteristics

Technical specifications

Inputs/Outputs