Let’s go ahead and acknowledge the elephant in the room right from the giddy-up: convincing most people that Marantz’s PM-KI Ruby integrated amplifier ($3999, all prices USD) is an affordable audio component might be a tough sell, especially given the number of highly lauded integrated amps available today for $1000 or less. So why are we reviewing the PM-KI Ruby on SoundStage! Access, a site dedicated to “reasonably priced hi-fi & home-theater equipment”?
Well, as I alluded to in an earlier blog post, written as I was unboxing the PM-KI Ruby, if “reasonably priced” is the territory I’m tasked with exploring here, I want to figure out where the boundaries of that mythical kingdom are. In other words, I requested a review sample of the PM-KI Ruby fully cognizant of the fact that it could be off the map in terms of that all-important price-to-performance ratio we’re in search of here. But to paraphrase Hunter S. Thompson, to search for the edge is to risk going over it.
At any rate, enough with the apologetics. Let’s discuss the PM-KI Ruby on its own terms. If you’re familiar with the history of the Marantz brand, you recognize “PM” as the designation used by the company for all its integrated amps. And the “KI” stands for Ken Ishiwata, the legendary audio engineer and Marantz brand ambassador whose personal tastes shaped the sound of the company’s gear for four decades.
The PM-KI Ruby and its companion piece, the SA-KI Ruby Super Audio CD player with DAC, are limited-edition pieces (1000 pieces each, 500 in a gold finish and 500 in black) created to celebrate those four decades of work—before Ishiwata left the company in May 2019, just six short months before his death—and share a lineage with a number of highly lauded KI Signature pieces from the brand’s history, including the PM-KI Pearl and SA-KI Pearl released in 2009 (pearl, of course, being the gemstone signifying the 30th anniversary, just as ruby represents the 40th).
The PM-KI Ruby isn’t the direct descendent of the PM-KI Pearl, mind you. Instead, you could think of it as a trickle-down-but-tweaked version of the company’s flagship PM-10 ($7999). So, in that sense, the PM-KI Ruby does represent something of a bargain. Like the PM-10, the PM-KI Ruby relies on class-D amplification. Whereas the PM-10 employs dual Hypex NCore NC500 modules per channel, the PM-KI Ruby sports one per channel, resulting in rated power output of 100Wpc into 8 ohms or 200Wpc into 4 ohms—half that of the PM-10.
Like the PM-10, the PM-KI Ruby is an all-analog design. All of the digital inputs and decoding have been offloaded to the aforementioned SA-KI Ruby Super Audio CD player with DAC. Unlike the PM-10, the PM-KI Ruby lacks a balanced signal path and features only single-ended inputs and outputs. It does, however, benefit from a discrete two-stage design, with separate power supplies for the preamp and power amplifier.
Despite the relative compactness of its chassis (5″H x 17.3″W x 17.8″D), the PM-KI Ruby weighs approximately as much as a newborn baby yak (~34.6 pounds). All told, it features six stereo analog audio inputs and two stereo analog audio outputs, as well as a headphone amplifier output and two sets of massive high-purity copper, five-way binding posts for speaker-level connections.
Two of the analog audio inputs are set apart from the rest in terms of both form and nomenclature. The CD and Phono inputs both sport thick nickel plating and are spaced significantly wider than other inputs, which simply carry the generic names Line 1, Line 2, Recording 1, and Recording 2.
The phono stage appears to me to be lifted straight out of the PM-10 and employs Marantz’s proprietary Musical Premium Phono EQ circuit, with support for both moving-magnet and moving-coil cartridges. MM input sensitivity is specified as 2.3mV/39k ohms; MC input sensitivity is specified as 250µV/100 ohms.
The back of the unit also features a stereo power amp input, which you could use in a home-theater bypass scenario should you so choose. Interestingly, though, there’s no way to access this input via the included remote control; you have to select it using the rotary input-selection knob on the front of the main unit. Doing so also disables the input-selection buttons on the remote entirely, until you de-select the power amp input via the front panel.
Also interestingly, although Marantz’s messaging indicates that the PM-KI Ruby can be connected to an external power amplifier via stereo preamp outputs, no such outputs exist. Which also means that you can’t connect a subwoofer directly to the amp via a line-level connection.
Setup and configuration options
If all of the above seemed to paint the PM-KI Ruby as somewhat simple and limited in terms of setup, my apologies. By way of a handful of other ins and outs and what-have-yous, the integrated amp can actually be configured several different ways—up to and including a full surround-sound setup. Two ports on the back of the chassis labeled F.C.B.S. (Floating Control Bus System) allow up to four PM-KI Ruby units to be ganged together as master and slave(s).
The simplest such configuration would be pairing two integrated amps together for a biamplified system. Going this route would also involve flipping the Stereo/Bi-Amp switch on the rear panel from the former to the latter setting.
But that’s just scratching the surface. Gang three of the units together and split the outputs from a multichannel SACD player, for example (L&R to one unit, surround L&R to another and center to a third, with the LFE output going straight from the player to a subwoofer), and you’ve got a complete 5.1 setup that’s roughly as practical as nipples on a Buick, but it’s nonetheless a possibility.
With only one KI-Ruby test unit to play with, my review system was a bit more typical, so I didn’t have to worry about flipping rear-panel switches, assigning F.C.B.S. ID numbers, or anything of the sort. I did, however, have one problem to solve before I settled down for some truly in-depth listening: what DAC would I be using with the PM-KI Ruby? The answer for most people buying this integrated amp would be the one built into the companion SA-KI Ruby. But I’m not reviewing that player.
I started off by connecting a little DAC I’ve fallen in love with here lately, the Topping E30, which I’m currently employing and enjoying the hell out of in a dedicated headphone setup. The E30 is USB powered, though, and it took mere seconds of listening to realize that the PM-KI Ruby is far too revealing an amp to partner with this particular DAC. The only way I could get the noise floor of the E30 anywhere near that of the PM-KI Ruby was to use a rechargeable USB battery pack, and that’s simply not practical for long listening sessions.
Next up, I tested the preamp output of my Sony UDA-1 USB DAC-amplifier. Again, it took only a bit of casual listening—before I even had my speakers properly positioned—to hear a bit of digital edginess to vocals that I’d never noticed in the UDA-1’s output. And needless to say, that doesn’t jibe with the PM-KI Ruby’s all-analog design.
So, on a whim, I pulled my old Oppo BDP-105 universal disc player out of storage, where it has sat since I upgraded both of my A/V systems to UHD. This proved a much better match for the PM-KI Ruby—and also gave me access to not only a great CD player but also a wonderful USB DAC—so I set about tweaking the rest of the system before kicking back for some in-depth evaluations.
Picking the right speakers to use with the Marantz was something of a process of elimination. Given that I didn’t have any unused subwoofers kicking around the house with speaker-level connections, I needed a full-range(ish) tower. I also didn’t want to use a hybrid powered speaker for obvious reasons. That narrowed down the list significantly, but in the end, I picked my trusted old pair of Paradigm Studio 100 v.5 towers, since I’m most familiar with their performance. For speaker-level connections, I relied on a pair of Elac Sensible speaker cables, pre-terminated with banana plugs, and for line-level connections I used Straight Wire Encore II analog audio interconnects.
Thankfully, none of the PM-KI Ruby’s settings needed to be tweaked before the system was ready to rock. And I say “thankfully,” because even the simplest of setup options can be a little convoluted to access. Within the setup menus, the only options are for switching the Phono EQ between the MM and MC settings, enabling or disabling Auto Standby, and adjusting the mute level attenuation (-20dB, -40dB, or -∞).
Even level balance and tone controls are a bit more complicated than they need to be, though, requiring you to press the Mode/Trim button on the remote and scroll through options using the Enter button, which is made all the more difficult by the fact that the circular D-pad on the remote isn’t the left/right/up/down/enter control we’ve all been programmed to assume it is, but rather the transport control for the SA-KI Ruby. Directional buttons and Enter are located above, near the very top, which makes them somewhat difficult to reach. Again, though, I accessed these controls only out of curiosity, not necessity, since I left all of the PM-KI Ruby’s settings on default. I merely mention it in case you’re a tone-tweaker or you might need to access any of the other settings.
Sitting down for some serious listening
After a few days of background listening and casual interaction, just to acclimate myself to the PM-KI Ruby’s remote control, I kicked off my critical evaluation of the amp with a playthrough of Joanna Newsom’s epic Ys on CD (Drag City DC303). While four of the album’s five lengthy cuts feature gorgeous orchestration by Van Dyke Parks—who also co-produced—the one song in particular that forced me to sit up and reckon with the amp’s capabilities is also the only one devoid of accompaniment other than Newsom’s own harp playing: “Sawdust & Diamonds.”
What struck me most was the way in which the PM-KI Ruby delivers the subtlest nuances of the recording—intimate details like Newsom’s teeth dragging across her lips and tongue at the end of fricative consonants, and the harmonic overtones accompanying her quasi-pubescent vocal cracks, like at 1:52 when she sings, “And the articulation / In our elbows and knees / Makes us buckle and we couple in endless increase / As the audience admires.”
I don’t mean to paint a picture of the PM-KI Ruby as an overly analytical amp. Far from it. Revealing, certainly. Detailed, no doubt. But along with that detail come sweetness and warmth that give the amp its unmistakable character and voice. It’s as if you took neutrality as a starting point and, rather than sculpting, did a bit of wet-sanding and polishing.
Which means that, while you can hear details in the recording that get a bit buried via lesser amps, you get none of the harshness or edginess that can often accompany Newsom’s uncontrolled explosions of adorable vocal awkwardness. But neither do you get a noticeably colored presentation of the music.
More than anything else, though, what I love about this song through this amp is the immediacy. The intimacy. It’s as if several feet of the space separating me from my speakers were deleted, as if the recording were holographically projected out into the room.
I reveled in that same sense of immediacy and intimacy with “Jimi Thing” from the Dave Matthews Band’s Under the Table and Dreaming (24-bit/44.1kHz FLAC, RCA Records/Qobuz). But more so than that, what really pulled my whiskers were the depth, width, and utter precision of the soundstage. The song kicks off with an acoustic guitar duet from Matthews and Tim Reynolds that sounds wall-to-wall and ten feet tall via the Marantz, and as with the Joanna Newsom cut, little details came through that may have otherwise gone unnoticed: the texture of the wound phosphor bronze strings, the sounds of fingerprints scraping across them, the occasional (very minor) fret noise. Far from distractions, little details like these make the music feel real, alive, organic, in the room with you.
As the rhythm section and vocals kicked in at around the 18-second mark, the PM-KI Ruby finally had the opportunity to flex its muscles in terms of dynamic punch and bass authority, both of which it excels at. As with the midrange and treble, there’s a uniqueness to the amp’s delivery of the lowest octaves, but it’s exceedingly subtle. In other words, while there’s no blatant tonal coloration here, there’s a welcome pinch of enhanced warmth and fullness to the bass that adds some liveliness to music like this without making it sound in any way unnatural.
It was during my second playthrough of this song that tragedy struck, though. My phone rang. And I’m sure that seems like no big deal to many of you, but I’m an anxious introvert, and talking on the phone under the best of conditions fills me with dread. But when I’m trying to listen to music? It’s near panic-inducing.
At any rate, I mention it only because this phone call turned out to be a happy accident. Rather than muting the amp, I simply walked over and turned down the volume. And when I was free from my telephonic torture session, I noticed something peculiar: the PM-KI Ruby still sounded good with the volume turned down low enough to accommodate a conversation. Like, really damned good.
Sure, bass and treble were both diminished to differing degrees. Fletcher-Munson curves are gonna do what Fletcher-Munson curves do. But the amp still delivered shockingly satisfying dynamics and detail at less-than-background listening levels, and the soundstage and imaging were still seriously impressive.
With the volume re-adjusted to proper listening levels, I cued up an old favorite that I’ve never heard at any audio show or dealer demo for some reason: “Some Broken Hearts Never Mend” by Don Williams from his underappreciated 1977 album Visions (16/44.1 FLAC, MCA Nashville/Qobuz). Before you chuckle, give it a listen. Garth Fundis’s mixing and engineering on the album are simply fantastic, and although it doesn’t take an amp of the caliber of the PM-KI Ruby to appreciate his work, it certainly doesn’t hurt. While a little contrived, the soundstage here sounds sumptuous, and the interplay between the palm-muted and barre-fretted guitars cuts through the mix via the Marantz in a way that a lot of amps can’t quite pull off.
The unmistakable timbres of Williams’s beautiful bass-baritone voice were also delivered with all of the aforementioned warmth, richness, and natural tonality. But the real star of the track is the pedal steel that dominates the bridge starting at around the 49-second mark. Through the Marantz it sounded positively ethereal, hovering in a tangible three-dimensional landscape of loping, frolicking rhythm.
Speaking of that rhythm, more so than just about any other track I auditioned, this one really revealed the PM-KI Ruby’s fantastic transient response. There’s simply a precision to the attack of the click-clocking percussion and the fingerpicked guitars that’s a cut above what you’ll hear from many an otherwise-fantastic amplifier.
Another track that I regularly pull out to gauge transient response is “Rickover’s Dream” from the SACD release of Michael Hedges’s Aerial Boundaries (Audio Fidelity AFZ 218). While the pitch-black background of the PM-KI Ruby did reveal that the noise floor of this recording is a little higher than I remembered, that did nothing to diminish the delicate beauty of the tapped harmonics that kick off the composition. Looking through my listening notes, I’m seeing the word “precision” repeated over and over and over again here, along with a turn of phrase that I’m not particularly proud of, but it tells a story worth telling: “Decay so natural it sounds as if the reverberation is sliding down the back wall like raindrops on a window.”
I think what most people would take away from the experience is the amp’s sometimes-startling dynamic capacity, though. There are times when Hedges assaults his guitar strings with such violent gusto that I usually keep the volume knob a little lower than usual, just to avoid clipping. And there have been times when I’ve blown speaker drivers with this song, despite thinking that the amp I was auditioning at the time had plenty of headroom. But the PM-KI Ruby honestly gobbles up these violent outbursts and begs for more without a hint of compression or saturation.
Generally speaking, I don’t put a whole lot of stock in headphone outputs built into integrated amps, but since Marantz specifically calls out the dedicated headphone section of the PM-KI Ruby and its discrete HDAM modules, I decided to plug in a few cans and give it a listen. Initially, I had two reservations about the headphone amp, but in the end only one of them ended up being a legitimate concern: the amp lacks a volume memory function, so whatever loudness level your knob is set to when you plug in your headphones is where it’s set for personal listening.
With my big, open-backed cans, like the Audeze LCD-2s, this didn’t prove to be much of a problem. Appropriate loudness for my Paradigm towers turned out to be exactly the right amount of juice for the headphones. With more sensitive earphones, like my custom Westone ES50 IEMs, I learned the hard way to give the volume knob a twist to the left before plugging in.
The second initial concern turned out to be nowhere near as valid. Typically, I look for headphone amps that have selectable gain, since too little gain can make my Audezes sound a bit flat and lifeless, and too much gain can make my Westones sound a bit too noisy. Even without such a setting, though, the PM-KI Ruby’s headphone output drove all of my cans and earphones with equal authority, impact, warmth, and detail, with a background just as black as I heard from my Paradigm speakers. I’ll spare you the laundry list, but digging through my collection of headphones of all shapes, sizes, and sensitivities, I couldn’t find a single pair that didn’t sound their best when plugged into the Marantz.
Comparing the Marantz PM-KI Ruby to its competitors
If you’re intrigued by the PM-KI Ruby but a little scared off by its price, you might also want to take a look at Marantz’s newer Model 30, which sells for significantly less at $2599. While the Model 30 was tuned by a different Marantz sound master, Yoshinori Ogata, it relies, as best I can tell, on the same amp modules, and features a near-identical set of inputs and outputs. There are a few key differences, though. Firstly, the Model 30 sports a fresh new look for Marantz, and its front panel is much more knob-adorned. Indeed, it features front-panel controls for MC/MM selection, tone, and balance, and although it lacks the PM-KI Ruby’s F.C.B.S. functionality, it does have preamp outputs, which will be handy if you want to connect a subwoofer.
Moving away from the Sound United family but sticking with the same budget range, I found that many of the things I loved about the PM-KI Ruby could also be said about the Naim Nait XS 3 ($3490). It’s similarly equipped in terms of inputs, although its phono stage doesn’t support MC cartridges. In terms of sound, the Nait XS 3 is—like the Marantz—full of personality. It’s a different personality, though. The Naim piece, to the best of my memory, couldn’t muster quite as much testosterone as the Marantz, nor was its soundstage as expansive. But it did sound ever-so-slightly livelier.
What about more budget-oriented integrated amps, though? My go-to recommendation for burgeoning hi-fi enthusiasts looking to max out that all-important bang-vs.-buck ratio is Denon’s PMA-150H ($1099), which—to be fair—is sort of playing an altogether different sport from the PM-KI Ruby. The PMA-150H is a fully packed digital tour de force with a built-in DAC and USB, coaxial, and optical digital inputs, as well as wireless streaming capabilities. In terms of analog inputs, it’s limited to two, and neither connects to a phono stage. Its amplifier section is also limited to 35Wpc into 8 ohms, although it does sport a subwoofer output. And its headphone output features a three-level impedance control. Despite its relative lack of power, the PMA-150H never struggled to drive my Paradigm Studio 100 v.5 towers to more-than-satisfying listening levels, although needless to say I couldn’t push them as hard as I did with the Marantz integrated amp. And it lacked some of its big brother’s bass authority and muscularity, as well as its ridiculously low noise floor and capacity for the nth degree of detail. But it’s still an incredible little integrated amp for the money.
TL;DR: Should you buy the PM-KI Ruby?
Whether or not Marantz’s PM-KI Ruby is the right integrated amp for you depends in large part on your needs. To be frank, it’s mostly aimed at hi-fi junkies who have a soft spot in their hearts for the legendary Ken Ishiwata. But if you’re an all-analog audiophile, or if you’re willing to spend another $3999 for the SA-KI Ruby to add digital decoding capabilities, there’s no denying that this gem of an amp earns its price tag.
The PM-KI Ruby does have some operational quirks, and its lack of preamp outputs is a disappointment. Plus, it does dip into diminishing returns territory in terms of its performance. That said, I’ve auditioned integrated amps costing twice as much or more that couldn’t legitimately be said to best the PM-KI Ruby in terms of detail, dynamics, refinement, soundstaging, and imaging. So even if you’re budget-conscious, its price isn’t unreasonable or extravagant. More like aspirational. Just note that, with a limited run of 1000 units, which have been on the market for over a year now, finding one to audition for yourself may be a challenge.
. . . Dennis Burger
- Speakers: Paradigm Studio 100 v.5
- Speaker cables: Elac Sensible speaker cables
- Interconnects: Straight Wire Encore II analog interconnects
- Source: Oppo BDP-105 Blu-ray player
- Power protection: SurgeX XR115 power conditioner
Marantz PM-KI Ruby Integrated Amplifier
Price: $3999 USD.
Warranty: Five years parts and labor.
Sound United, LLC
5541 Fermi Ct
Carlsbad, CA 92008
Phone: (844) 298-5032