Rega Isis CD Player & Osiris Integrated Amplifier (Playback, from TAS 213)

Integrated amplifiers,
Disc players,
Digital-to-analog converters
Rega Isis,
Rega Osiris
Rega Isis CD Player & Osiris Integrated Amplifier (Playback, from TAS 213)

The Isis CD player and Osiris integrated amplifier ($8995 each) are, by a very wide margin, the most ambitious audio components ever produced by the British firm Rega Research, and as such they represent what some might consider a radical departure from the firm’s past offerings. After all, most Rega products have been mid-priced overachievers—not premium-priced components looking to storm the gates of high-end audio. Since past performance is often the best indicator of a company’s future behavior, the Isis and Osiris raise an inevitable question: Does Rega really have what it takes to be a player in high-end audio’s top-tier?

To be perfectly candid, I came upon this review full of skepticism and doubt, not because I haven’t found past Rega products good (many I’ve tried have been very good), but rather because I am aware that in the high end of high-end audio, “good” just isn’t good enough. It also does not help that many mid-tier manufacturers have previously tried and failed to take this quantum step upward. The problem, more often than not, is that aspiring mid-tier players who aim high but fall short largely do so because they end up producing expensive and exceptionally well-built components that still sound pretty much like well-executed pieces of mid-tier equipment. What’s often missing, I think, is the kind of breathtaking, extraordinary, stop-listeners-in-their-tracks sound quality that is the hallmark of all true top-tier components.

Let me begin this review by telling you that, over the months they have been in my reference system, Rega’s Isis and Osiris have proven time and again that they are no mere wannabes. On the contrary, they’ve convinced me they are in every way the genuine articles, and are—believe it or not—legitimate contenders for crème de la crème honors in their price range. The sound quality of Rega’s flagship components require no apologies. While some have questioned whether Rega has abandoned its value-oriented roots or simply over-reached by building the Isis and Osiris, I see the pair as marking a point of redefinition or rebirth for Rega, so that all that has come before from the firm has been merely a prelude. In short, the Isis and Osiris show what those plucky and creative Brits can really do when they pull out all the stops, flex their design muscles, and embrace the concept of British exceptionalism (a term that really does apply here).

In a moment I’ll discuss the qualities that make the sound of the Isis and Osiris exceptional, but first let me explain some of their key construction details.

Inside Rega’s Isis and Osiris

The Isis is the Rega’s seventh-generation CD player design, and it leverages all that the firm has learned in creating its first six generations of players. Modest to a fault, Rega characterizes the Isis as more an evolutionary than revolutionary design, though in practice it sounds dramatically different and better than previous Rega players.

Differences begin with the Isis’ chassis, whose panels are precision CNC-milled from thick slabs of aluminum, then bolted together to form a beefy, vibration-resistant platform for the components within. Like all Rega CD players, the Isis is a top-loader, but one whose drive motor and laser/lens assemblies have been rigorously hand-selected and “blueprinted.” Unlike many top-loaders, the Isis doesn’t use any sort of weighted puck to clamp discs to its motor spindle; instead, the motor is fitted with a precisely machined combination spindle/ball-chuck mechanism that locks CD firmly in place (meaning you’ll hear a soft, reassuring “click” as you snap CD’s into position).

Component-parts-matching for the Isis is extremely selective so that Rega actually chooses three hand-matched sets of laser/lens assemblies for each unit; one set gets installed in the player you buy, while the other two are marked and held in reserve at the factory for use as spares should your player ever require them. The drive mechanism and laser/lens assembly is controlled by a custom CD control chipset and software developed specifically for Rega by a British partner, with two objectives in mind. First, the Isis is set up to “test-read” each CD and then to adjust and optimize its laser/lens positioning algorithms to match the specific characteristics of the disc (meaning that laser positioning is fine-tuned on a disc-by-disc basis).

Rega says this process means the Isis “will often play discs with marks or scratches that other players cannot read.” Second, the CD chip-set includes an unusually large 20MB data buffer, which CD control software leverages to allow extra time for an extremely powerful 32-bit DSP engine to run extensive error-detection/correction algorithms, to help clean up digital audio data before passing it along to the Isis’ DACs. Rega contends that, “previous chipsets always made compromises on error correction,” so that it was “possible of have good jog resistance or better musical performance.” But with the Isis CD control chip-set, Rega claims it is now possible to optimize both at once.

The Isis also uses a proprietary, high-precision phase-locked loop master clock and feeds data to a pair of Burr Brown PCM1794 DACs “running in a parallel dual-mono mode,” which in turn drive “a high performance discrete Class A current-to-voltage amplifier”—an amplification stage that Rega says is critical to the Isis’ overall sound. Circuitry for this current-to-voltage stage draws upon the circuit topology of Rega’s Ios phonostage—an extremely low-noise/low-distortion circuit geared for use with low-output moving-coil phono cartridges. The current-to-voltage stage then drives “an enhanced discrete Class A output amplifier,” which offers a circuit that is “fully balanced from the digital-to-analog converters to the balanced XLR outputs.” The Isis also provides single-ended analog outputs, along with TosLink and coaxial S/PDIF digital outputs.

Rega has left no stone unturned in its quest for higher performance with the Isis, paying close attention even to seemingly minor details such as the physical composition of the unit’s printed circuit boards, or striving to reduce noise between digital and analog sections of the player through the use of “RF ground-plane techniques.” Similarly, the Isis provides not one but three dedicated power supplies: one for the player’s digital audio section, another for its analog section, and a third for its CD control chipset and front panel display. Moreover, both the digital and analog power supplies have their own dedicated 50VA mains transformers (so that the supplies are galvanically isolated from one another), with each supply featuring 10 separate power supply regulators. Finally, in support of computer audio enthusiasts, the Isis provides a “double-clocked USB interface” that is—you guessed it—fed by a dedicated power supply that is galvanically isolated “from the main circuitry of the Isis player.”

Finally, recognizing that execution details count for a lot in the upper tier, the Isis comes packed in a sturdy wooden transit crate, and is supplied with an extremely high-quality power cable, plus a set of Rega-branded, Klotz-manufactured, Neutrik connector-equipped Couple interconnect cables. Also in keeping with its upscale mission profile, the Isis includes one of the most beautifully made and intuitively organized remote controls I have ever seen (the outer case of the remote is milled from two blocks of aluminum).

The Osiris, in turn, is a deceptively compact-looking beast of an integrated amp, weighing in at a beefy 56.4 pounds. Like the Isis, the Osiris features a heavily built chassis whose panels have been CNC-milled from aluminum billet, with the left and right chassis panels each protecting banks of heat sinks that run along the side of the amp from front to rear.

Rega describes the Osiris as a “super-high-performance dual-mono amplifier” that has been designed “around a ‘minimalist’ high-gain power amplifier and ‘passive preamplifier’ circuit topology”—a topology in which there is only “a passive volume control and a single stage of power amplification between the input and speaker (ensuring the signal path remains as short and clean as possible).” The passive volume control is an ultra-high-quality motorized Alps Blue Velvet potentiometer that is dead quiet and silky smooth in operation. The high-gain power amplifier, in turn, uses “a fully symmetrical circuit throughout and low-distortion, high-linearity-and-bandwidth, common-base voltage-amplifier driver stage,” said to enable the Osiris “to drive any speaker system with the minimum of distortion.” The Osiris employs “eight Sanken 200-watt output transistors … in a ‘triple’ high-current output stage enabling the Osiris to drive even the most awkward of speaker systems with ease.”

The signal path of the Osiris uses extremely high-quality capacitors (e.g., Nichicon audio-grade capacitors and Mundorf Mcap polypropylene capacitors) and other premium components, while the amp’s “open and closed loop feedback levels and gain bandwidth product components are optimized to give a tight and controlled sound stage, especially at the low-frequency end of the audio range.”

As with the Isis, Rega has taken great pains with the Osiris’ dual power supplies, each of which features a 400A toroidal transformer, fast-recovery rectifier diodes, and “40,000µF of Rega K-Power smoothing capacitors per channel.” The resulting power supplies are said to provide “more than enough current to drive the hardest of loads.” Input and low-level driver stages of the amplifier are “fed from a regulated symmetrical-tracking power supply with a low-noise voltage reference, which provides a fully stabilized low-noise voltage, ensuring the highest sonic purity.” Also with an eye toward further maximizing purity, the Osiris is configured so that “all the dedicated audio power supplies feed only the audio circuits,” (italics are mine), whereas the amp’s “input switch relays, front-panel display and micro-controller, and protection circuits have their own dedicated power supplies.”

The Osiris provides one fully balanced analog audio input, which, interestingly, uses a transformer in place of a traditional “electronically balanced input circuit,” with the transformer built to the same low-noise/low-distortion standards as the one used in the firm’s Ios moving-coil phonostage.

Like the Isis, the Osiris comes packed in a wooden crate, is supplied with a high-quality power cord, and comes with a beautiful, heavily built remote. One thoughtful detail touch is that the Osiris remote not only can control the amp, but also provides the essential controls necessary to run the Isis.

In Egyptian mythology, Osiris was not only regarded as the god of the underworld, but also—more importantly—as the god who grants life and rebirth. How appropriate, then, that Rega chose this name for what has proven to be one of the most expressive and dynamically lifelike amps I’ve ever heard, regardless of price. The perceived excellence of the Osiris hinges on three key characteristics: expressive dynamics, three-dimensional soundstaging, and superb delineation of low-level details. Let’s talk about each of these in turn.

First, the Osiris handles both macro- and micro-shifts in dynamic emphasis more effectively than any integrated amp (and most separates) I’ve heard—including some offering more than three times the raw power output of the Osiris. But perhaps this is because there is nothing “raw” about the manner in which the Osiris delivers power to answer the needs of the music. For starters, it does a stunning job of handling finely graduated shades of dynamic contrasts both within and between musical phrases. In practice, this means the listener might at one moment enjoy how suave and nuanced the Osiris sounds when playing quietly, only to be stunned the next moment by the amp’s turn-on-a-dime ability to explode into fast-breaking, large-scale musical swells. It isn’t that the Osiris sounds powerful or can play loudly without compression (although it does both); it is the almost shocking combination of subtlety and speed with which it delivers energy on demand that sets it apart.

For compelling examples of these qualities in action, try listening to the middle movement (Scherzo: Kräftig, nicht zu schnell) of Mahler’s Symphony No. 5 (Michael Tilson-Thomas/San Francisco Symphony, hybrid SACD) through the Osiris. The movement is a study in contrasts, emphasizing through its various twists and turns both lilting and gently modulated string, woodwind, and percussion passages, yet also abruptly shifting gears to present violent, volcanic brass and low percussion section eruptions. What makes the Osiris so impressive is that it is perfectly at ease with both sets of musical demands, gracefully revealing almost subliminal string section modulations in one moment, then fiercely uncoiling to hammer home bass drum “thwacks” or blistering brass-section fortissimos in the next.

Unlike some of the passive preamp/active power amp combos I’ve heard, the Osiris never quashes low-level dynamic information, but rather seems to hold an abundant supply of gain in reserve. As a result, Osiris differentiates itself from many competitors through its uncanny ability to faithfully track the exact shape of a given instrument’s dynamic envelope—enabling listeners to hear precisely how and when energy is released as notes are launched, allowed to sustain, and then to decay into silence. Because of its sheer dynamic realism, the Osiris tends to sound markedly more expressive and alive than many competing amps do—in a sense making competitors sound as if a compressor has subtly throttled their outputs. What the Osiris forcefully demonstrates is that sonic “detail” is not purely a matter of focus, resolution, and textural acuity (though the Osiris delivers those important qualities too), but also depends upon dynamic realism.

If, for example, you put on recordings of blues artists Albert Collins or Stevie Ray Vaughan playing their signature electric guitars (Collins on a Fender Telecaster and Vaughan on his famous Stratocaster), the Osiris will clearly show that the instruments differ significantly in the ways they attack and sustain notes. When Collins plays a lead line played on the bridge pickup of his Tele, the notes have a certain fierce, penetrating, fast-rising, and almost percussive quality that cuts through the mix in an unmistakable way. In constrast, Vaughan’s Strat is not quite so fierce-sounding at the onset of a note, but it typically exhibits a more full-bodied “singing” tonality, with notes that sustain a bit longer and decay more gradually. The Osiris makes distinctions like these easy—and then essential—for listeners to grasp.

The Osiris proved, too, to be a brilliant soundstager, and though perhaps not quite as good in this respect as the very expensive ASR Emitter II amp I once heard at Harry Pearson’s home, it was still exceptionally good in its own right. When substituting the Osiris in my system, the effect was that of hearing soundstages stretch and expand dramatically in depth and especially width, and with this increase in stage size came a more realistic sense of the performers’ positions upon the stage. By this I do not mean to suggest that imaging specificity became unnaturally “hyper-focused” (a high-end phenomenon that, while admittedly fascinating and appealing in its way, really doesn’t sound much like live music does). Instead, I mean that on good recordings the Osiris conveyed a sense of actual performers interacting within real spaces, so that I could not only tell where performers were on stage, but could also hear their instruments’ playing off of nearby reflective surfaces, and so on. Similarly, the Osiris makes child’s play of exposing the differences between real acoustic reverberations and reflections vs. electronic effects applied in the studio in an effort to simulate reverberations.

In practice, I found the Osiris let most speakers (actually all of the speakers I’ve tried with the amp thus far) produce more focused images and more holographic soundstages than I experienced when powering the speakers by competing amps. With lesser amps, I found, “soundstaging” seemed to take the form of building up layered stacks or “sheets” of sonic information—almost as if you were to place a series of colored transparencies on top of one another. While this approach does provide multiple “layers” of information and conveys fore-and-aft depth to some degree, the problem is that each layer of information, taken in isolation, seems more or less flat. But in contrast, the Osiris (and the Isis, too) presents soundstage depth and width information in (to borrow Harry Pearson’s famous phrase) a much more continuous way, so that you sense the scale of individual instruments and the general shape, size, and acoustic properties of the recording spaces in which they play.

All of this may be a roundabout way of observing that the Osiris and Isis both do a phenomenally good job of reproducing low-level sonic details, in the process giving the listener a much more vivid and believable sense of the music’s textural, timbral, transient, and especially spatial content. And as we’ll see in a moment, natural-sounding detail is a shared strength of both the Osiris amp and Isis CD player.

Isis: Goddess of Nature and Magic

Turning again to Egyptian mythology, we see that Isis was not only the wife of Osiris, but also regarded as the goddess of nature and magic—two qualities that help define the singular appeal of Rega’s Isis CD player. And just as there was synergy between the mythological Isis and Osiris, there is real magic in the pairing of the Isis player with its companion Osiris amp.

Let’s begin my noting that while both the Isis and Osiris reproduce low-level sonic information in an effortless way, they definitely do not wear resolving power on their sleeves like high-end audio “badges of honor.” Instead, both components render event the subtlest and most fine-grained musical details in a refreshingly smooth and natural-sounding way. Sadly, some audio journalists have mistaken the Isis’ and Osiris’ eminently natural presentation for a certain lack of focus or definition, which is simply not the case. Depending upon the material you choose to play, these Rega components can and often do deliver a tightly focused sound with razor-sharp definition, conveying tons of low-level information in the process. But the key, here, is that they do so without losing track of the musical whole.

Delineation Without Deconstruction

The problem with audio components that makes definition or detail ends in themselves is that they not only delineate elements of music (which can be a good thing), but also tend to deconstruct the music—leaving the listener with a disjointed collection of musical pieces and parts (almost like an unfortunate frog dissected on a laboratory table). What we want, or at least what I want, however, are components that can beautifully delineate musical lines and themes (inviting listeners to follow individual musical threads, just as they might do at a live concert), yet that clearly conveys a sense of the musical whole, leaving it gloriously intact. And that, my audio compadres, is precisely what the Isis and Osiris do best.

To hear these capabilities play out in real-world listening contexts, try putting on a track that features a multiplicity of instrumental voices, and whose recording quality accurately captures a rich mix of textural, transient, and spatial details. For me, one such piece is the title track from the jazz album Floratone [EMI], which feature the eclectic guitarist Bill Frisell, the adventurous percussionist Matt Chamberlain, and a cast of like-minded cohorts, including Viktor Krauss on bass, Ron Miles on cornet, and Eyvind Kang on viola.

“Floratone” opens with a dark, brooding bass drum rhythm figure against which the taut pop of a snare drum and other percussion instruments inject a piquant counterpoint. Through the Isis and Osiris, you’ll hear almost breathtakingly palpable skin sounds from the drumheads, the snap and sizzle of the snare, and delicate, almost fleeting “click” and shimmer of hi-hats at play. But what is just as important is the way the combined sounds of the percussion instruments expand to fill the room, defining a large, reverberant soundstage upon which the rest of the song will unfold.

Within seconds, the percussion instruments are joined by the profound earthy sound of Krauss’ sharply descending syncopated bass lines, and an intense, angular statement from Frisell’s guitar. As each instrument joins the ensemble, you become aware of two things. First, the voices the instruments sound whole, complete, and utterly able to stand on their own, independent from one another (just as real instruments in an ensemble sound when they are heard from up close). Second, you perceive implied relationships between the performers and their instruments, partly through the conventional mechanisms of melody, rhythm, and counterpoint, but also through spatial cues that help anchor the instruments within the soundstage. So, you not only hear the instruments themselves, but also the air between and behind them, which conveys both a sense of place and of interaction and communication among the ensemble members. Nowhere is this more apparent than when the soft, melancholy voice of Miles’ cornet enters, and you hear the other instrumentalists bending out of the way in order to create sonic space for the horn. Interestingly, even when the producers combine electronic effects and reverb with natural acoustic sound, you can hear them deliberately place those synthetic sounds within the broader framework of the acoustic soundstage. The result is a song that is beautiful in its variety and complexity, and almost hypnotic in its ability to pull the listener into the three-dimensional world of the performance space—as if to more clearly grasp the messages embodied in the music.

Let’s be blunt; you don’t get listening experiences like these from just any old audio components—not even from some very good and expensive ones. But what makes the Rega pieces so special—so natural and magical at the same time—is that they continually supply streams of contextual information that helps make the music more intelligible, richer in meaning.

I’ve already said I found the Osiris more expressive than other integrated amps I’ve tried, but the Isis is no slouch either. As an experiment, I did a side-by-side comparison between the Isis and my long-term reference—an oldie-but-goodie vacuum-tube-equipped Musical Fidelity kW SACD player. From this comparison I learned several things. First, I found the big kW offered a little more tube-induced harmonic bloom up high, and also just a touch more wallop down in the bottom octave. But I also found the Rega offered greater resolving power and a far more holistic and three-dimensional presentation overall. Through the Isis, instruments as well as the air and spaces between them took on a palpable and almost sculptural solidity; in short, with the Rega in play there was undeniably more “there” there. One practical note to observe, however, is that in order to hear the Isis at its best you absolutely must use its balanced XLR outputs; the single-ended outputs sound good, but they lose some of the player’s inherently magical qualities.

While I don’t think the Isis offers the almost supernatural smoothness and fluidity of, say, Meridian’s 808.3 CD player or the (in my experience) incomparable resolving power of the dCS stack, I do think it may offer the next best alternative to those two über-expensive world-class players, and at a substantially lower (though by no means cheap) price. Finally, I should mention that I used the Isis’ USB input to play digital audio files from my computer, and found it to be, hands-down, the most compelling USB DAC I’ve yet heard (though with the caveat that the Isis makes no provisions for handling higher-than-CD-resolution files).

A Few Caveats

Isis: Ideally, I wish the Isis provided coaxial S/PDIF and TosLink digital audio inputs in addition to its USB input, and I also wish its DAC supported high-res file formats. Together, these improvements would make the player more “future-proof” and relevant for computer audiophiles. Tube aficionados may want to know that there is a tube-powered version of the player, called the Valve Isis ($9995), though I personally prefer what I perceive as the purer, more focused sound of the solid-state version. Finally, I should mention that listeners should expect a perceptible delay between pushing “Play” and actually hearing the music start, since it takes a while to fill the Isis’ large audio data buffer.

Osiris: One small ergonomic concern is that the amp’s high-quality speaker binding posts are deeply recessed and shrouded by thick, protruding chassis panels. In practice this means there’s not much maneuvering room when using beefy, spade-lug-equipped speaker cables (which, I find, amps of this caliber require). Second, note that while the Osiris provides a power amp input (which can be used as a home-theater bypass), it does not provide a variable-level preamp output (possibly because its passive-front-end/single-stage-amp topology does not readily allow this).

How Good Are The Isis and Osiris, Really?

As I mentioned earlier, I approached this review with skepticism and doubt, I suppose because—down deep—I feared Rega might build merely “good” components for a market segment where sonic greatness is required. But now that I’ve lived with the Isis and Osiris for months and experienced their capabilities firsthand, I see them in a completely different light. Where once I wondered whether the Rega pieces could keep up with established, pedigreed leaders in their class, I now find myself asking whether competitors can in fact keep up with the Isis and Osiris. They really are that good.

For my part, I’ve purchased the review samples, partly because they’re a delight to listen to, but also because they are powerful reviewing tools that shed plenty of light on ancillary components with which they are used. But frankly, you should not be unduly influenced by my purchase decision, since we all must make our own choices in this game. Instead, my only hope is that this review will inspire you to go out and give the Isis and Osiris a careful and open-minded listen, and then to draw your own conclusions. Whether you decide to embrace the Isis and Osiris or not, I’m confident you’ll find their performance eye-opening, to say the very least.


Rega Isis CD player
Disc types: Red Book CD, MP3, or WMA
Digital inputs: USB at data rates to 16-bit/48kHz
Digital outputs: TosLink and coaxial S/PDIF
Analog outputs: Two stereo (one single-ended pair via RCA jacks, one fully balanced pair via XLR jacks).
Frequency response: 17Hz–20kHz +/-0.1dB, THD + Noise: < 0.0013%
Dimensions: 17.1" x 4.4" x 13.4"
Weight: 41.9 lbs.
Price: $8995

Rega Osiris solid-state integrated amplifier
Power output: 162Wpc into 8 ohms, 250Wpc into 4 ohms
Analog inputs/outputs: Four single-end stereo inputs (via RCA jacks), one stereo record input (via RCA jacks), one stereo record output (via RCA jacks), one fully balanced stereo input (via XLR jacks), one stereo direct amp input (home-theater bypass via RCA jacks)
Frequency response: 20Hz–26kHz, +0/-0.5dB; 10Hz (-1.7dB point), 75kHz (-3dB point)
THD + Noise: < 0.05% (bandwidth 22Hz–30kHz)
Dimensions: 17.1" x 4.8" x 13.8"
Weight: 56.4 lbs.
Price: $8995

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(972) 234-0182

Analog: Nottingham Analogue Systems Ace-Space 294 tonearm/Space 294 turntable; Fosgate Signature phonostage; Shelter 901 MkII, 9000, and Harmony MC moving coil phono cartridges.
Digital: Musical Fidelity kW SACD player.
Amplification: Musical Fidelity kW500 integrated amplifier; NuForce P-9 preamplifier and Reference 9 v.3 Special Edition monoblock amplifiers.
Headphones, etc.: HiFiMAN EF-5 and Burson HA-160 headphone amplifiers; Audeze LCD-2, HiFiMAN HE-5LE and HE-6 planar magnetic headphones; Shure SRH-840 dynamic headphones; JH Audio JH 16 PRO, Westone ES-5, and Ultimate Ears In-Ear Reference Monitor custom-fit in-ear monitors; and Monster Turbine Pro Copper Edition and Westone True Fit 4 universal-fit in-ear headphones.
Cables: Chord Select balanced interconnects; Furutech Lineflux digital/interconnect cables and Speakerflux speaker cables; NuForce Focused-Field digital/interconnect and speaker cables; Furutech Powerflux power cables.
Power Conditioners & Acoustic Treatments: PS Audio Soloist in-wall power conditioner, Furutech Daytona 303 power conditioner; Auralex Studiofoam and RPG B.A.D. (binary amplitude diffsorber) acoustic treatment panels.

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