Review: SPL Phonitor X headphone amplifier

SPL’s Phonitor X headphone amp, and pre-amplifier.

I’ve got a somewhat complicated relationship status with headphone listening. It’s something we’re working through, and perhaps I’m being too needy. The thing is I feel that I’m getting shortchanged on the big listening experience I’m used to from my two-channel rig. In an effort to address this emotional attachment to my loudspeakers I dipped my toe into the head-fidelity pool, and committed to a couple of headphone amps for a month to see if I was capable of an open audio relationship.

Did it feel like cheating when I unpacked, and slid on the Sennheiser HD800 for the first time? A bit, but I guess that is part of the thrill of exploring high fidelity.

The Phonitor

Because I received the $2,499 USD ($3,399 CAN) SPL Phonitor X, and a Naim DAC-V1 ($2,100 USD $2,795 CAN) at the same time for review from Element Acoustics, and did a lot of my listening going back-and-forth between the two for comparison, I’m going to make this a two-part headphone, and headphone amplifier review. I’ll start here with the Phonitor X, and will be following up with the DAC-V1 very soon. I also had the MrSpeakers EtherFlow, and the Audeze LCD-3 Fazor in for review along with the 800, so this will also be a comparison of how these three well-known cans rated against each other, and how they responded to each head-amp.

Audeze LCD-3 Fazor $1,945 USD ($2,645 CAN).
Sennheiser HD800 $1,399 USD ($1,899 CAN).
MrSpeakers EtherFlow $1,849 USD ($2,495 CAN).

The Phonitor X can handle five stereo sources with the optional DAC installed (which this unit did), these are balanced XLR, unbalanced RCA, USB, coaxial and optical inputs. It also features SPL’s Voltair 120V-rail technology which the company claims is “…four times as high as in standard audio designs. 120V Rail Technology is our reference technology developed and manufactured to run on an operating voltage of 120 volts, which corresponds to twice that of discrete operational amplifiers and four-times that of semiconductor operational amplifiers.” It also has the ability to have the volume adjusted with any IR remote control thanks to a “learning” feature.

The SPL Phonitor X possesses some very unique technical circuitry options for the discerning listener, and with up to 3.7 watts of output it can even double as a pre-amplifier for power amps or powered monitors. The unique circuit I’m referring to is what SPL calls their Matrix system, and its function is to emulate the time-delayed effect inherent to loudspeaker listening. SPL claims their Matrix circuit  “delivers the most realistic playback on headphones. As almost all music was mixed for speaker playback the Phonitor Matrix lets you experience music on headphones as being played back through speakers.”

Detail of SPL Phonitor X Matrix controls.

Controls for the matrix circuit can be enabled or disabled, and include Crossfeed, and Angle adjustments.  From SPL:


“The Crossfeed switch allows you to adjust the frequency-dependent crossfeed simulation of both channels by adjustments of interaural level difference – as if this characteristic would be heard from monitors when in their own room ambience. One can compare variations in crossfeed values as approximating the influence of different room sizes and characteristics on a given loudspeaker setup. This adjustment can be made in six steps ranging from “minimum” to “maximum.” Crossfeed interacts with the Angle value to simulate the width of a stereo image.”


“The Angle switch provides for frequency-dependent simulation of your stereo image width by adjustments of interaural time difference. This influences the moment in time at which a signal’s wave form arrives at the ear and corresponds to a particular variation in the angle of an actual loudspeaker pair. The time constants of the interaural time differences between the left, and right channels occur within a range of 90 to 635 microseconds. As a starting value  we recommend selecting the 30° position.”

After listening to dozens of albums through the SPL in the course of the last month I found that the settings that worked best for me varied from album to album, and even different masterings of the same album. I chose two albums for each set of headphone/amp reviews: I chose them for how different they were from each other, because they sound great to me, and because I enjoyed listening to them so much.

This headphone amp/DAC is very well constructed, with a level of fit, and finish being what one would expect from a multi-thousand-dollar unit. It feels solid, all knobs, and switches move in a very precise, chunky manner that was very pleasing from a tactile standpoint. It’s controls are well laid out, with my only wish for change being the location of the dip switches (which control output gain, and VU-meter sensitivity) from the bottom of the unit to the side for ease of access. The VU meters are not only practical, but visually appealing, especially in low-light situations, and can be quite hypnotic to watch while listening. The included operating instructions were clear, and precise.

*After several initial listening sessions of the Phonitor X I received the PerfectWave P10 Power Plant from PS Audio for review, and upon installing it into my system I perceived an immediate uptick in clarity, and timing of the sonic presentation, and a noticeable drop in the noise floor. All my review listening notes on the Phonitor X were written after hooking it up to the P10. Look for an upcoming review detailing the P10’s capabilities.

Hooking up the SPL amp was very straightforward, and took only a few minutes. The following are my listening notes which I wrote over a two-day period.

The rig: Mr.Speakers EtherFlow with Tidal lossless 16/44 file. Volume level at 11 o’clock. USB out from MacBook Air with WireWorld Platinum Starlight USB cable.

EtherFlow detail.

At_The_Black_Hawk_3This is a straight-ahead hard bop LP – the third of four sets – recorded on the evenings of September 22~24, 1959, at The Black Hawk jazz club in San Francisco’s Tenderloin district. It’s an exquisite live recording with a staggering amount of air, and detail captured from the venue. To me these sets are a masterpiece of live recording, and I place it firmly alongside the Bill Evans Trio Sunday at the Village VanguardThe sound stage is extremely lifelike in it’s presentation, with a very large aural landscape rendered by the SPL amp through the MrSpeakers, with a very low noise floor allowing all the detail of this live recording to come through:patrons glasses, and cutlery tinkling at tables, snatches of conversation from the audience, a cash register, general background activity – it all translates through – but never does the placement of these goings-on in the mix interfere with what Manne and his Men are up to on the stage. The performers’ placement in 3D space never wavers, or floats around. It is presented as rock solid. This is a 16/44 file but never once while listening through the Phonitor X did I get the sense that anything was lacking in detail or resolution – more the opposite. The reproduction of Richie Kamuca on tenor sax, and Joe Gordon blowing trumpet absolutely floored me with the rich, burnished hue of brassy timbre lent to both instruments in this set. The depth, and body of Manne’s drumming was preternatural in it’s physicality, and had visceral impact when called upon throughout the LP, in particular on Black Hawk Blues. The metal-tinged blossom of decay off the cymbals on every tap of Manne’s sticks was rendered with enough space around it for a fade-away jump shot. Ditto Manne’s skin work on the snare, and Toms – both had a lot of meat on the bone. Monty Budwig’s finger, and fret work on the bass possessed real organic grit throughout with palpable oomph, and snap off the strings, particularly at the lower octaves.

The rig: Audeze LCD-3 with Tidal lossless 16/44 files. Volume level at 11 o’clock. USB out from MacBook Air with WireWorld Platinum Starlight USB cable.

LCD-3 detail.

A touch more crispness on leading-edge trumpet notes from Gordon’s horn, and a slightly more forward placement to his position on the sound stage tipped the Audeze’s 3D-hat early on this album. Presentation was definitely more forward in the recording compared to the EtherFlow of both Gordon, and Kamuca on sax, with Victor Feldman’s work on the piano placed solidly back, and to my left in the mix. Manne was deep-v’eed down the centre with outreach into the right, and left at a realistic arm’s length. Budwig’s bass kept itself in the lower left on “Whisper Not”, and the SPL/Audeze combo gave up plenty of texture off his strings, with every bit of finger fret play, and skin slap/slide clearly articulated. Audience feedback, and clapping flowed out very naturally both to the rear right, and left with a scattering of applause always revealing itself directly behind my head. This comes courtesy of the Phonitor X Matrix circuitry which I adjusted several times while listening. Matrix provided startling clarity, and ultra-realistic placement of the performers, and audience members. On several occasions (with all three headphones) it caused me to jump around in my lounger thinking the dog had knocked something over in the kitchen, or bumped into something in the living room off to my left or behind me – when it was merely a server taking drinks away, or someone walking past from a position close to a mic in the club, and bumping into a chair or table – which proved in my mind that SPL is definitely on to something with this technology. Once again, the incredibly low noise floor of the SPL allowed micro-details to come to the fore of the recording, and remove another layer in the suspension of disbelief. Timbre, and tone possessed a real human touch, and characterized this combo as one of musicality, and realism with perhaps a touch more bass/percussion depth and texture from the LCD-3 than the EtherFlow.

The rig: Sennheiser 800 with Tidal lossless 16/44 files. Volume level at 11 o’clock. USB out from MacBook Air with WireWorld Platinum Starlight USB cable.

HD800 detail.

The 800 played to its strengths more immediately through the SPL than other amps I’ve heard them through. Whether it was the Phonitor X’s Matrix circuit stereo-image tuning ability, or just the beefy rail voltage, the 800 produced the most dynamic and, balanced presentation of this recording of the three headphones. While they still suffered slightly from edginess on the highest notes from horns, and a bit of ringing on piano, their linear, open response allowed the recording space to really open up all around the presented sound stage. The illusion of room boundaries was pushed out much further than either the EtherFlow, or LCD-3 were capable of with this album. Budwig’s bass lacked ultimate depth (but not texture), and Manne’s percussive insistence was not as fleshy in its impact, but the presentation of the audience in around the band was absolutely convincing, so the tradeoff in the realism of the recorded space made up for those minor shortfalls in my estimation.  Performers were possessed of life-sized scale in their presentation – never an easy feat even on two-channel rigs, rare in my experience for headphones – and were imbued with real physical presence in the mix. While performers notes overlapped throughout the musical thread of each track, they did so without any congestion or smearing. Tone, and timbre – hallmarks of any amplifier’s ability to portray instruments, and voices with conviction – were exquisitely executed with the Sennheiser reproducing every subtle nuance of playback, and human syncopation of each artist on the stage. Speed of attack on leading edges of Feldman’s piano work, and the subtle spatial cues from the decay off Manne’s cymbals, high-hat, and floor Tom continued to reinforce the illusion of the Black Hawk’s low-ceilinged, curtained-draped space.

The rig: Sennheiser 800 with Tidal lossless 16/44 files. Volume level at 11 o’clock. USB out from MacBook Air with WireWorld Platinum Starlight USB cable.

Sennheiser HD800 ear pad detail.

Christian-Loffler-MareChristian Löffler’s 2016 LP Mare is a deep-house electronic dreamscape filled with throbbing, hypnotic percussion/bass lines. It features many complex layers of interleaving instrumentation, vocals, and sound effects that create an out-of-body listening experience once you give yourself over to it. The opening track Myiami opens with a deep soundscape of tinkling glass/chimes effects spaced all around one’s head like a star field through the 800 with tight, fast, percussion placed well back in the mix, but expanding forward with decay, and presence on every hit. Build up of instrumentation, and all the subtle inflections of the layering Löffler employs in song construction is beautifully nuanced. The illusion of depth, texture, and sonic flavour most convincing in its realism. The next cut –Haul – starts with an insistent beat which immediately activated my body’s response of head bobbing, and created a real sense of unease, and sadness as the minor third plays out over Mona Steinwidder’s haunting vocals. The large sound stage presented by the 800 once again seems to be one of the real strengths of the Sennheiser. It has the ability to put you in a recorded space that pushes the boundaries of traditional headphone expectations for spatial reproduction. Complex electronic instrumentation, and effects are placed evenly in 3D-space with a weight to the location more behind the ear’s centreline focal-plane which constantly made the music feel like it was creeping ever forward and through your skull. Speed, and transparency are key to the 800 sound IMHO, and the tradeoffs that seem inherent to their stock sound are a rolled-off bass, a forward treble, and a linearity to the presentation that balances the treble/mids/bass very evenhandedly. But what you get back is the sensation of timing accuracy, and a larger envelope for the music to breathe in. I think that the SPL’s Matrix circuit brings out the best in the Senns, but that a warmer, more forgiving cable could flesh out the bass, and attenuate the forward treble.

The rig: Audeze LCD-3 with Tidal lossless 16/44 files. Volume level at 11 o’clock. USB out from MacBook Air with WireWorld Platinum Starlight USB cable.

LCD-3 connection detail.

A more forgiving treble than the 800, but no less accurate or insistent in its ability to focus the ear on electronic micro details in the upper registers, the LCD-3 had a slightly more closed-in soundstage, with a more “cupped-ears” feel to the moody keyboard work on display throughout the album. Bass is more fleshed out, with a sense of weight that the 800 didn’t fully grasp, but again the trade-off here is a smaller sense of the recorded space, especially with air, and decay on Mona Steinwidder’s insinuating-sadness vocal work. The insistent percussive push is still strongly translated by the Audeze, with the Phonitor’s meaty mid-bass reproduction spilling over from the lower octaves, albeit in a manner that enhances the spacey experience of the deep house Löffler is laying down in these tracks. This is a far warmer overall presentation than the 800, but with that uptick in sonic temperature comes a perceived sense of ever-so-slight smearing, and fuzziness in the top end compared to the Sennheiser. But the balance is paid back with that bass/midrange depth, and tonal colour. So here again, despite the same amp/cabling/source/volume level a very different presentation, and again, a presentation about tradeoffs. The fact that the SPL is able to rend so much individuality from these three disparate cans – and ultimately make each uniquely musical, and tremendously enjoyable – says a lot about the amp’s design, and ultimate purpose. Rather than making everything sound similar, it excels at differentiating every song through every headphone: the sign of a supremely well-designed product in my experience.

The rig: MrSpeakers EtherFlow with Tidal lossless 16/44 files. Volume level at 11 o’clock. USB out from MacBook Air with WireWorld Platinum Starlight USB cable.

EtherFlow headband detail.

The EtherFlow/SPL pairing offered excellent electronic bass-line rendition/definition on leading edges in particular: fully formed, with real depth, size, and weight to the beat. The EtherFlow strikes a balance between the 800 and the Audeze on this album, with all the weight, and meat on the bone of the LCD-3, but with a more open, ethereal top end akin to the 800, with a larger sound stage than the Audeze. Steinwidder’s voice keeps it’s haunting sadness but with more wet texture to her enunciation without sacrificing the addictive sibilance of her performance. Electronic instrumentation is well spaced in the mix without any smearing, or clustering together of sounds. There’s a smoothness to the speed of percussion, and keyboards on the EtherFlow but they still maintain an underlying grain pattern that differentiates each layer without any circuit-hash clogging up all the electronic minutiae Löffler packs into every track. Well-balanced tonal colour keeps the sound human, engaging, and musical without mechanical pacing creeping into any sameness from track-to-track. A malady that can afflict some electronica in my experience. The SPL’s timing, and pitch betray a slight lean towards accuracy over ultimate musicality in its voicing, but it never comes with a price that sounds too high for that particular tradeoff.  The EtherFlow pulls off a sonic coup with Mare by being able to handle all the moving pieces of this album without sacrificing its palpable, emotional engagement for the sake of ultimate bass, danceability or relentless electronic saturation.


While kicking back on my sofa, and queuing up music on the big rig is still my preferred choice of high-fidelity relationship, the SPL Phonitor X was able to consistently inspire me to seek its company, and the singular music-listening experience it provided. It’s a great communicator of emotion, tempo, and musicality regardless of the headphone I paired it with. It’s sound definitely opened up, and smoothed out with use. At about the hundred-hour mark of playing music through it everything seemed to settle down, and I didn’t notice any further breaking-in peculiarities to playback. It is capable of transporting the listener to the recorded moment with transparency, and sonically speaking it was not fatiguing in the least, even after hours-long listening sessions. The same couldn’t be said for all three headphones used in this review. While each one brought a unique, and significant skill set to bear during my time with them, and all three ‘phones possess not only audiophile-quality playback qualities I covet such as 3D-imaging, instrument, and voice separation, lifelike timbre, and tone, and the all-important emotional connection to the music, none could be comfortably worn for more than 30-40 minutes at a time without a short break. Over-ear comfort/fit was outstanding on all three, but I’m talking specifically about the headband. The most comfortable was the HD800, followed by the EtherFlow, and the LCD-3. The weight of each definitely played a factor in how long I could listen for, and I think that overall, comfort is the biggest factor that stops me from committing outright to headphones.

It would be very difficult to choose which headphone I liked the best sonically at this point, because each traded the top spot from album to album, or genre to genre. Different recordings playing to varying strengths in each design. When I finish Part Two of this extended review using the HD800, EtherFlow, and LCD-3 with the Naim DAC V-1, I’ll be in a better position to voice an opinion on which headphone I’d be ready to settle down with. Until then, thanks for reading this very long review, I hope you enjoyed it, and it answered some questions you may have had if you were, like me, buy-curious about a high-end headphone amp, and headphones.

–Rafe Arnott

SPL Phonitor X specifications

XLR Input

  • Neutrik XLR, balanced, Pin 2 = (+)
  • Impedance: ca. 20 kohms
  • CMR: -82 dBu (at 1 kHz)
  • Max. Input Level: +32.5 dBu

RCA Input

  • RCA, unbalanced (single-ended)
  • Impedance: ca. 10 kohms
  • Max. Input Level: +32.5 dBu

Digital Inputs (optional)

  • Coaxial SPDIF (RCA)
  • Optisch TOSLINK (F06)
  • USB (B)
  • Sample Rates (kHz): 44.1, 48 , 88.2, 96, 176.4, 192

Balanced Headphone Output

  • Neutrik 4-pin XLR connector
  • Pin wiring: 1= L (+), 2= L (-), 3= R (+), 4= R (-)
  • Impedance: 0.36 ohms
  • Damping Factor: 180 @ 40 ohms
  • Frequency Range: 10 Hz to 300 kHz ( -3 dB)
  • Crosstalk at 1kHz: -90 dB
  • THD & N: 0.00091 % (at 0 dBu, 1kHz, 100 kohms load)
  • Noise (A-weighted): -98 dBu
  • Dynamic Range: 130.5 dB

Unbalanced Headphone Output

  • 6.35 mm TRS connector
  • Pin wiring: Tip = Left, Ring = Right, Sleeve = GND
  • Impedance: 0.18 ohm
  • Attenuation Factor: 180 @ 40 ohms
  • Frequency Range: 10 Hz to 300 kHz ( -3 dB)
  • Crosstalk at 1kHz: -90 dB
  • THD & N: 0.00091% (at 0 dBu, 1 kHz, 100 kohms load)
  • Noise (A-weighted): -103 dB
  • Dynamic Range: 135.5 dB

Max. Output Power (at +30 dBu @ 1 kHz)

  • 2 x 1 W at 600 Ohm impedance
  • 2 x 2 W at 300 Ohm impedance
  • 2x 3.7 W at 120 Ohm impedance
  • 2x 2.9 W at 47 Ohm impedance
  • 2x 2.7 W at 32 Ohm impedance

Speaker/Line Outputs

  • Neutrik XLR, balanced, Pin 2 = (+)
  • RCA, unbalanced (single-ended)
  • Frequency Range: 4 Hz to 300 kHz (-3 dB)
  • Crosstalk at 1 kHz: -106 dB
  • THD & N: 0.00085 % (at 0 dBu, 1 kHz, 100 kohms load)
  • Noise (A-weighted): -103.8 dB
  • Dynamic Range: 136.3 dB

Internal Operating Voltages

  • Analog: +/- 60 V
  • Digital: + 5 V and + 3,3 V (optional)

Power Supply

  • Mains voltage (switchable): 230 V AC / 50 Hz or 115 V AC / 60 Hz
  • Fuses: 230 V: T 500 mA; 115 V: T 1 A
  • Power consumption: max 40 VA
  • Stand-by power consumption: 0.7 W

Dimensions (incl. feet)

  • 278 mm W x 100 mm H x 335mm D
  • 10.95 in W x 3.94 in H x 11.19 in D


  • 4.3 kg; 9.5 lbs (unit only)
  • 5.4 kg; 11.9 lbs (shipping)

About Rafe Arnott 389 Articles
Editor of InnerFidelity and AudioStream


  1. Great review, I enjoy your writing style and look forward to your reviews. Are you going to try the SPL as a Pre-Amp?
    Thanks for the review and photos.

  2. Okay, I read this a couple of days ago and then watched the “Phonitor Matrix explained” video on SPL’s website, which demos how the tech works through your own headphones. And since then I’m ruined. I mean, I was never a big headphones guy, and I used to put up with the differences between headphones and my standard no-phones setup because I can’t really set up a sweet 2-channel system without annoying other folks trying work, too. Or when my wife is sleeping and I don’t want to be a jerk. But now? Now my headphones just piss me off. And they piss me off because now I know the extreme stereo effect cans typically produce compared to monitors, the kind of effect that can feel like nobody is in front of me, just right next to each ear, all that can totally be corrected.

    Kudos to the engineers at SPL, seriously. I’m totally blown away and I haven’t even heard the thing in the flesh yet.

  3. Thanks for turning me on to the Shelly Manne live record! I’m a fan of Manne, but had yet to hear this fantastic recording..listening to Vol3 via Tidal/Roon now. Doesn’t look like these are available on vinyl.

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