Stereophile Spin Doctor on the Moonriver 505

When Michael Trei sat down to write Spin Doctor #18 for Stereophile, he had two unusually flexible pieces of analog gear on the rack: DS Audio's new E3 optical cartridge and equalizer (US$2,750 the pair), and Moonriver Audio's first phono preamplifier — the Model 505. Founded in Malmö, Sweden, in 2015 by George Polychronidis, Moonriver shipped its first product, the 404 integrated, in 2019. The 505 took another five years to perfect.

Four arms, every parameter

The 505 is hybrid — not in the tubes-and-transistors sense, but a deliberate blend of integrated-circuit gain stages and discrete output topology, all solid-state. Up to four tonearms can be wired in simultaneously, with gain, loading, capacitance, and EQ settings stored independently per input via an onboard microcontroller. Switch between turntables and the 505 instantly recalls every parameter without a menu in sight.

“A Swiss Army knife of a phono stage. With four inputs and an impressive array of adjustments, it can handle just about any combination of arms and cartridges.”

— Michael Trei — Stereophile

How it sounds

Trei reports a presentation that is simultaneously smooth and incisive — sibilance is well-controlled, bass has clear texture and weight, and the noise floor sits low enough to let the optical E3's signature transient speed come through unfiltered. Vocals are dug into rather than glossed over; piano material reveals "the attack of each chord perfectly." The 505's hybrid architecture pays off in the way most listeners hope hybrids will: a body and ease that read as discrete, with the noise-floor advantage of well-chosen op-amps.

Optical pairing

Optical cartridges live or die by the equalizer that follows them, but the 505 is no equalizer — it's a phono stage with the loading flexibility to handle anything else you might own. In the Spin Doctor system, the 505 took the E3's analog output and let it do what it does best: tantalisingly close to DS Audio's flagship Master Series performance at a fraction of the price. Trei's verdict on the E3 alone is glowing; on the 505, it is unequivocal.

Verdict

"Looks elegant, is built to last, and sounds wonderful." That's Trei's three-line summary, and after a long stretch with the 505 in our showroom we don't have a thing to add. If you own more than one turntable — or one turntable and more arms than sense — the 505 is the phono stage to put under it.