Luxman P-1u

Originally published on July 11, 2010
 
Note: this review is an exact cross-post from post #1 of this thread on Head-Fi, which contains some user discussion on the review that may be relevant to read: http://www.head-fi.org/t/501781/mini-reviews-luxman-p-1u-and-p-200

Intro

First, thanks to Todd @ TTVJ for allowing me (and the other people in this loaner program) to audition the Luxman P-1u at home for serious evaluative listening. I wanted to participate in this loaner program because I've had a long-running interest in desktop solid-state amps for a few years now, and I also have previous experience with both the Luxman P-1 (at a Head-Fi meet) and P-200 (which I also had in my home for a few days of critical listening last year).

A disclaimer I want to add is that I consider this to be more of a mini-review, given the limited time that this loaner program allowed me to keep the amp for (approximately 2 weeks). Reviews I've written on Head-Fi in the past were done with listening periods over a few weeks, or in some cases, even months. My review methodology has always been to listen and re-listen daily (or as often as possible) so I can re-check my ongoing impressions of a piece of equipment (and usually with just 1 headphone per week). A time period of ~2 weeks did not allow for too much re-listening so this mini-review lacks the thoroughness of previous reviews that I've written.

Reviewer Biases

My view of a headphone system is "source first" followed by headphones and then amp. In other words, a source of highest quality possible (assuming recordings of high quality also) should be paired with the most preferential-sounding headphone(s), to be driven by the most technically-optimal amp. In my view, the most technically-optimal amp is the one that provides sufficient power for all headphones being used without inflecting its own sonic signature, or minimally at least.

All previously owned (or heard, in some cases) equipment is listed in my profile for reference.

Equipment Setup

- Plinius CD-101 (CD player) (power cord: Signal Cable Silver Resolution Reference - directly into wall)
- BPT IC-SL RCA & Analysis Plus Silver Oval RCA/XLR interconnects
- AKG K701 (re-cabled with SAA Equinox), Audio-Technica AD2000 (re-cabled with APS V3), Beyerdynamic T1 (stock cable), Grado HP1000/HP2 (re-cabled with APS V3), Sennheiser HD800 (stock cable), & Sony Qualia 010 (re-cabled with Moon Audio Black Dragon)
- comparison headphone amp: SPL Auditor

Functionality & Operation

The P-1u has a form factor that allows for easy rackmounting, which I personally liked, even though I don't currently own a rack - I like it because this kind of form factor usually allows components to be stacked, which I took advantage of. The amp has quite a few features - dual single-ended headphone jacks, balanced XLR and unbalanced RCA inputs, balanced XLR phase inversion, and loop output (which I neglected to test, but I assume it's loop output).

Operationally there's nothing unusual about the amp - everything on it works as expected. There was only one thing I noticed, and it was that the amp didn't activate immediately upon power-on, similar to the P-200. The LED next to the power button lights up faintly first, and then after a few seconds, the amp fully powers up, which is noted by an audible internal click (presumably from relays) and then the LED becomes brighter at that point.

with: AKG K701

Music used for this headphone:
-* Alison Krauss & Union Station - New Favorite - "Let Me Touch You For Awhile"
-* Andrea Parker - Kiss My Arp - "Melodious Thunk", "Elements of Style"
-* Orbital - The Middle of Nowhere - "Way Out", "Know Where to Run"
- Priscilla Ahn - A Good Day - "Dream"
- Robert Planet & Alison Krauss - Raising Sand - "Trampled Rose"
-* The Crystal Method - Community Service - "Breakin On The Streets (False Prophet Remix)", "Dude In The Moon (Luna Mix)"

As the K701 is a difficult load in general for headphone amps, I used it primarily to determine the P-1u's driving ability, using the music marked with asterisks above, and the P-1u easily passed what I tested for - namely, audible distortion in any part of the frequency spectrum at very high volume. I cranked up the volume to the 2 o'clock position (way past ear-safe level) and checked for audible distortion in either the bass or treble, and there was none, and it still sounded like the P-1u had power to spare too. I could not say the same for the P-200 back when I tested it for this last year.

So the P-1u could drive the K701 well enough, and how did it sound? Not bad, though since my opinion of the K701 has since degraded over the years that I've had it (I got in April 2006), it means that sonically there was nothing I could fault the K701 for. Most parts of its innate sound were intact as far as I could tell. The P-1u seemed to reduce the K701's soundstage a bit (which is a good thing in my book) and drew out longer mid-range tones too and imbued female vocals with even more presence, compared to the SPL Auditor.

with: Audio-Technica AD2000

Music used for this headphone:
- Massive Attack - Heligoland - "Pray for Rain"
- Megadeth - Countdown to Extinction [MFSL] - "Sweating Bullets"
- Neotropic - Mr. Brubaker's Strawberry Alarm Clock - "Mr. Brubaker's Strawberry Alarm Clock"
- Orbital - Snivilisation - "I Wish I Had Duck Feet", "Are We Here?"
- The Crystal Method - Tweekend - "Murder", "Ten Miles Back"
- The Prodigy - The Fat of the Land - "Smack My B***h Up", "Fuel My Fire"

The AD2000 is the primary headphone I use to listen to electronica and metal, because it does 3 things really well that work for this kind of music: it's really dang fast (as in impulse response), it has excellent bass extension (and the bass quantity & balance is perfect for my tastes), and it's actually relatively flat in the treble. The music I used for this headphone is all music that can be seen as stressing any kind of headphone, but what makes the AD2K stand out is that it easily plays all of that music without breaking a sweat.

With that said, it's because of the AD2K's strengths that it actually takes a bad amp (or at least, a less than stellar one) to sonically subtract from this headphone, and unfortunately I found a couple aspects in which the Luxman P-1u was "less than stellar" compared to the SPL Auditor ("Luxman" and "SPL" from here on out). Probably the one quality I noticed the most was that the Luxman outright slowed down the AD2K's impulse response while the SPL did not. The Luxman reduced the AD2K's speed enough that percussive pops didn't "pop", spring-coil vibrations didn't "vibrate", brush stroke-like impacts weren't completely rendered, fast-note separations weren't completely separated, and there was even a kind of "blur" on fast multi-note passages. The Luxman also inflected a different tonal balance compared to the SPL that negatively affected the AD2K's bass response, in that it didn't provide as much bass weight and depth (in the 50-80Hz area).

Despite these flaws I found with the AD2K, the Luxman was still able to provide a satisfactory sound that provided a higher level of enjoyment, at least in terms of a "fun" sound. It did have excellent bass extension (and even seemed to drive slightly more power into ultra-low bass rumbles) but what made the bass in general stand out was a thick, meaty presence that was also very visceral and vicious, that made The Prodigy's "Fuel My Fire" a blast to listen to. And even if the Luxman wasn't all that fast, it still sounded as if it were enthusiastic because more often than not percussive hits sounded really "hard" - they just weren't "hard & fast" as they should have been.

with: Beyerdynamic T1

Music used for this headphone:
- Beyond Twilight - Section X - "The Path of Darkness"
- Dissection - Storm of the Light's Bane - "Unhallowed", "Thorns of Crimson Death"
- In Flames - The Jester Race - "Moonshield", "Artifacts of the Black Rain"
- Julia Fischer - Bach Concertos - "Concerto for two violins in D minor: Allegro (3rd movement)"
- Katie Melua - Piece by Piece - "Shy Boy", "On The Road Again"
- Megadeth - Countdown to Extinction [MFSL] - "Sweating Bullets"
- Symphony X - Paradise Lost - "Domination", "The Walls of Babylon"

It was with this headphone that I really was able to notice a general difference in frequency balance between the Luxman and SPL - the Luxman seemed to be more mid-range focused, while the SPL seemed to be more treble-focused. There was also a difference in soundstage and presentation that was noticed: the Luxman had a smaller soundstage and a more-forward presentation while the SPL had a bigger soundstage in comparison (more virtual air and space) and also sounded more laid-back. The SPL also had a very "separated" sound (musical elements distinctly placed in the soundstage out and away from each other on clear x-, y-, and z-axes) while the Luxman had less of this diffusion and more of a cohesive, less-separated sound.

I wouldn't say that metal music is necessarily ideal for this headphone, but I used some of it anyway just because I felt like it. And for metal music, the SPL certainly had a strength - it was clear-sounding, fast, & precise, with a very good forward-moving insistence too. Metal sounded more engaging on the Luxman though, because that amp's more-forward presentation sounded more assaulting and it had the fuller, thicker mid-range. The "diffusion" of the SPL also did not seem to work very well for metal either, at least on the T1 (it didn't matter much on the AT AD2K).

On the one Baroque-classical track, I thought it played more to the SPL's strengths than the Luxman's, as the SPL had the clearer sound, with wider, deeper imaging. It was also more "expressive" on the violins with greater dynamics and more apparent detail on bowing movements (like the speed of a bow stroke, or reversal of direction, for example).

It's possible that the SPL may be better-suited for driving the T1 than the Luxman but I wasn't able to look into this fully. I would've liked to have ABX'd the two amps against each other with the T1 more but ran out of time.

with: Grado HP1000/HP2

Music used for this headphone:
- Julia Fischer - Bach Concertos - "Concerto for two violins in D minor: Largo ma non tanto (2nd movement)"
- Dave Brubeck - Time Out [Legacy Edition] - "Take Five"
- Renee Fleming - Thais - "Meditation"
- Steve Kuhn - Mostly Coltrane - "Song of Praise"

Now that the sound of the Luxman and SPL amps was starting to emerge to my ears, I ran through only a short selection of music to play to the HP1000's strengths - classical-type music and jazz. Both amps did well with the HP2, but I'd give the edge to the Luxman. While instrumental tones sounded more trebly "brilliant" on the SPL (highlighting violins, for example), they were deeper on the Luxman, affording a higher sense of body, fullness, texture, and overall physicality. This worked well for the jazz selections in particular and made them sound more alive and engaging. The tenor sax on Steve Kuhn's "Song of Praise" for example sounded more connected with the musical group on the Luxman than on the SPL and even a bit more "soulful".

I haven't heard too many other amps with the HP2 and can't speak directly to previous amp experiences, and the Luxman sounded fine with it, but I felt that there are probably better amps to seek out for the HP1000 - even in my own experience earlier this year I felt the Woo Audio WA22 might be better-suited as it did not have the Luxman's reduction in the soundstage.

with: Sennheiser HD800

Music used for this headphone:
- Dave Brubeck - Time Out [Legacy Edition] - "Take Five"
- Julia Fischer - Bach Concertos - "Concerto for two violins in D minor: Allegro (3rd movement)"
- Porcupine Tree - In Absentia - "Blackest Eyes"
- Trifonic - Emergence - "Emergence", "Transgenic"
- miscellaneous metal

There was really no contest with this headphone - the Luxman was clearly the better amp for the HD800 than the SPL. IMO one of the HD800's worst qualities is its overly large soundstage that does not adapt to the size on the recording and the Luxman's forced reduction was actually a good thing in this case, because for me the expanded soundstage with the SPL downright detracted from the listening experience. The soundstage with the Luxman was a step in the right drection for a better sense of realism - but it wasn't completely realistic, it just got closer.

The HD800's overall treble-tilted frequency response benefitted a lot from the Luxman, as the musical selections sounded wispy and wimpy on the SPL, as if lacking gut and flesh (forget about body). While the SPL did help out in the aspect of treble articulation (another of the HD800's flaws IMO), it did very few favors for the HD800 - take a treble-tilted headphone and pair it with a treble-tilted amp, and you get a lot of treble. Now I personally like treble (a LOT in fact), but this particular combo did not appeal to my ears and made the treble sound bad.

The Luxman/HD800 combo, on the other hand, was a great example of synergy. Soundstage was actually precise, as it was easier to locate sounds and discern definite points in the virtual space. There was a good illusion of a center point too. The SPL, in contrast, made it feel like instruments were everywhere and nowhere at the same time. The Luxman also brought out the mid-range and mid-bass for a balance that sounded good on the HD800 - still not enough that I thought it was the perfect balance necessarily, but good enough to fix the HD800's main weak spots. It made the HD800 actually sound physical and tactile, and drums were even nicely impactful and powerful (specifically the ones on Dave Brubeck's "Take Five"). There was also a good full-range thrash and meaty sound to the overdriven guitars on Porcupine Tree's "Blackest Eyes." Even for the random metal tracks that I spun, the Luxman made the HD800 sound pretty good with the added mid-range/mid-bass and smaller soundstage - but this didn't really make the HD800 ideal for metal, as I think that metal is one genre that the HD800 almost completely fails in, and the Luxman didn't rectify any of its issues for that kind of music for me.

with: Sony Qualia 010

Music used for this headphone:
- Alison Krauss - Forget About It - "Ghost In This House", "It Don't Matter Now"
- Alison Krauss & Union Station - Lonely Runs Both Ways - "Unionhouse Branch", "Doesn't Have To Be This Way"
- Alison Krauss & Union Station - New Favorite - "The Boy Who Wouldn't Hoe Corn"
- Global Communication - 76:14 - "4:02", "9:39"
- Laika - Sounds of the Satellites - "Almost Sleeping"

There wasn't much left to evaluate the Luxman for by this point, but I continued anyway for the final speed and treble tests. And in the aspect of treble, it was expected that the SPL would beat the Luxman, and it did. It had more quantity and was substantially cleaner and clearer, properly rendering fast plucks, creaks, vibrations, etc. In some instances, the Luxman even felt hazy. But to its credit, the Luxman balanced against the SPL's shortcomings in texture and mid-bass weight, and its soundstage reduction worked well on the Qualia too. The Qualia did reveal one thing none of the other headphones really caught though, and that was a sense of "silence" to the background on the Luxman. The sonic background of the SPL never really felt "dead" or "black," while it did on the Luxman - and it definitely seemed like the Luxman was the "quieter" amp too. As in, it had a better ability to convey quiet-volume passages in music, while the SPL seemed to struggle with this and sounded louder and didn't contrast soft versus louder very well.

Testing

There were a few non-music tests that I was compelled to do to wrap up my auditioning of the Luxman, and these included checking it for any noise whatsoever (no music playing & no input), checking the fine-tuning ability of the fixed gain, and comparing the balanced XLR to the unbalanced RCA input.

Noise: I used my always dependable highly-sensitive Audio-Technica AD2000 for this test and cranked up the volume to max with no music playing and nothing on the input. The amp was completely silent at minimum volume and as I turned up the knob, but at maximum there was an extremely slight high-frequency feedback of some type. It was very minimal though, I had to strain to hear it - but it was definitely there as I repeated this test several times and heard it every time. I also checked the SPL and it did not have the silence of the Luxman - it had what sounded like power transformer feedback, very slight, but was audible at any volume level (even zero).

Gain: For this test I spun some music and used again the AD2000, slowly turning up the volume knob from zero and listening to the adjustment of volume. Both amps had a nice low gain that allowed for proper fine-tuning on the AD2000 to achieve just about any desired volume with proper channel balance too at lower volumes. The SPL allowed for slightly more precision though in comparison.

XLR vs RCA input: For this test I used both of my pairs of Analysis Plus Silver Oval RCA and XLR interconnects along with the HD800, which I know improves in balanced mode (not that the Luxman has balanced output, but if I was going to hear a difference, the HD800 would reveal it). The only difference I could hear (after properly calibrating the volume between XLR and RCA of course) was a more dimensional soundstage on the XLR input that provided more air and space between instruments, and made them sound farther away. The Plinius CD-101 does not have true dual-differential output on its XLRs though, so I suspect there would probably be more sonic difference with true-balanced sources.

Summary

Throughout my listening of the Luxman P-1u, it proved to be a capable-enough amp for my headphones but it was far from ideal for a few of them, and given its price of $3K, I don't think I would buy one either. It wasn't really what I was expecting coming after the Luxman P-200 last year and if I had to pick one of them, it'd probably be the P-200.

I know that there will be people looking for a recommendation for or against this amp but I can't give one. Perception of sound is too subjective for that kind of thing and this was only my experience. Others will probably have different experiences. It's overall a fine amp, it just didn't particularly work for me sonically.

If you bought an headphone amp like you might buy a regular speaker amp, the P-1u is exactly what you'd get. Typically for Luxman, the build quality is excellent and beautiful to behold.  While I didn't test the P-1u, nor its predecessor, the P-1, with anything exotic, every pair of headphones I've plugged in to it didn't give me pause at all to think about the capabilities of the amp in the slightest.
 
Comparing it to the Audio-gd Phoenix, the Luxman is revealed to be very slightly on the sweet side of neutral, with more authoritative bass, but with marginally less smoothness and detail. It also doesn't have the massively wide soundstage that the Phoenix balanced did with my HD-800s, but this is less of a surprise. More of a surprise was the cheap Alps RK27 volume attenuator, which doesn't seem fitting for such a high-end amp. It is not purely "straight wire with gain" but, again typically for Luxman, the amp you get when you don't want to have to ponder all the complexities, but have it "just work" and sound good regardless. To boot, you can plug it in to either a single-ended or balanced source, so compatibility is not an issue.  
 
The only downside is the asking price, which at $3000 from TTVJ (around $1000 more than the Japanese retail price) is extremely serious amp money, more than the cost of quite a few balanced amps. This, however, might be moot if one never wants nor needs to re-cable a stock pair of headphones. 
 
If you have they money to spend on such a high-end rig, but can't be bothered messing around trying to work out what will work best with your headphones, then this is the amp to go for.

 
LUXMAN P-1u REVIEW:
 
I just finished spending 2 weeks with the Luxman P-1u headphone amplifier from Todd @ TTVJ and this amp was a pleasure to listen to.  I just shipped it back two days ago, but if I didn't already have an Eddie Current ZDT amp then I would have been sorely tempted to try to buy the Luxman which ranks among the best dynamic headphone amps that I have tried.  Thanks for the opportunity Todd!
 
GEAR:  I used a Samsung DVD > Synergistic Research active shielded coax cable > PS Audio Perfectwave DAC > anti-cables XLR and RCA IC > Luxman P-1u > HD800 with Locus-Design Hyperion cable.  I also used my Macbook Pro as source via optical out > Emotiva and sysconcept.ca optical cable.  And I used an Apple 802.11n only Airport Express at 5Ghz to connect to my iTunes library on my iMac (which seems to have no stutters or drop outs).  I used the Luxman power cord that came with it, plugged into a simple APC computer UPS which does a good job keeping everything quiet.  I'm sad to say that I didn't use my vinyl rig as source because I had to return my Nighthawk in order to pay for a dental implant. My cheap GEMsound phono preamp is not up to the task and doesn't perform well with my Benz Micro ACE Red L moving coil cartridge.  It was too much trouble to reinstall my Ortofan Blue MM cart for my current preamp since I plan to either get another nighthawk or a TTVJ phono preamp later. In the photos you'll see that the TT made a good stand for setting up the P-1u.
 

 
MUSIC (24/96 only where noted, otherwise 16/44 lossless):  
 
* Diana Krall - Live in Paris
* Peter Asplund - As Knights Concur
* John H. Clarke - Acoustic Guitar (bought off CDBaby.com) 
* Nils Lofgren - Acoustic Live
* Tord Gustavsen Trio - "Restored, Returned" 
* Esbjorn Svensen Trio - From Gagarin's Point of View 
* Mattias Svensson Bill Mays Joe La Barbera - Head up High
* Sara K. - "Hobo" 24/96
* Jack Johnson - In Between Dreams, On and On, and Sleep Through the Static
* Jimmy Cobb Quartet - Jazz in the Key of Blues 24/96
* Shelby Lynn - Just a Little Lovin
* Nancy Bryan - Neon Angel 24/96
* Joel Styzens - Relax Your Ears (bought off CDBaby.com)
* Wendy Sutter - Songs & Poems For Solo Cello
* Bob James Trio - Straight Up 24/96
* Eva Cassidy - Live at Blues Alley, Time after Time
* Ottmar Liebert & Luna Negra - Up Close 24/96
* HDTracks.com - Open Your Ears 24/96
* Bill Evans - Waltz for Debby
* Carla Lother - 100 Lovers 24/96
* Infected Mushroom - B.P. Empire
* Pink Floyd - Animals
* Led Zepelin - Mothership
* Bella Sonus - Enamoured
 
HEADPHONES:  In addition to the re-cabled HE800 above, I tried a wide variety of headphones and IEM with it, including my difficult to drive AKG 600 ohm K240M, K1000 and Smeggy SFI pucks, the easier to drive HD600 with APS V3 cable, HiFiMan HE-5 LE and original HE-5, and my very easy to drive LA7000 and HF-2, along with my very sensitive and low impedance JH13Pro custom IEM with TWag cable.  I did not bother to re-install the stock HD800 cable, since it adds some upper mid/treble colorations of the headphone and would make the HD800 an inferior tool for assessing the performance of the P-1u.  The HD800, HE-5/5LE, LA7000 and JH13Pro were the best phones for assessing the performance of the P-1u, while the others had some weakness or coloration that rendered them less useful.  Nevertheless, the P-1u was able to drive all these headphones well, and there is not another amp in the house that these phones work better with (with the exception of the K1000).
 
COMPARISONS:  I compared the Luxman side by side to my Eddie Current ZDT, maxed Woo WA6 with pseudo dual power supply and Sophia Princess 274b rectifier, ALO Amphora, and Nuforce HDP.  After trying four different 12AX7/5751 tubes in the ZDT over the past year, I settled on the Sylvania gold pin 5751 as having the most natural and extended treble while sounding more refined than the stock Mullard re-issue 12AX7.  For A/B comparisons I could plug the PWD XLR out into the Luxman and then use the PWD RCA out to feed the other amp, and then listen to two amps with the same source at the same time.  This allowed for quick switching between amps using one headphone, after volume matching with my Radio Shack SPL meter.  I have also tried the PWD's RCA output into the Luxman and compared that to the XLR input, with little differences in sound quality between the two. Finally, I also tried the Luxman's RCA loop-out into the ZDT and compared it to the RCA loop-out on my Woo WES, and found them to both be quite good in sound quality with little difference from directly out of the PWD.  
 
As per requests, I also compared the Luxman with several dynamic phones to my WES with Stax O2 Mk1; where the HE-5 LE were the closest to Stax in terms of sound signature and soundstage but the HD800 closest in terms of detail and speed.  However, the Stax rig gave me all that in one headphone (minus the HD800 soundstage), but with the addition of a bit more bass in return for slightly less but more than adequate max volume.
 
FEATURES:  The Luxman P-1u may at first seem to offer few features or bells and whistles, as it doesn't seem to be loaded up with knobs and buttons, but that is not the case.  Like my ZDT it has multiple inputs, but while the ZDT has 3 RCA inputs, the P-1u can accept one RCA and one XLR input which you can switch between.  Even though the P-1u doesn't offer a balanced output like the ZDT, having the XLR input is better for when your source only has XLR out (Neko DA100 DAC or some phono preamps for example).  The ZDT uses output transformers to convert the signal into a balanced output, but if I want to feed a balanced signal into the ZDT I have to use an external input transformer, which introduces an extra set of interconnects and transformer into the mix.  
 
Both the P-1u and ZDT allow connecting two sets of headphones at the same time, without any reduction in sound quality.  However, the P-1u has two 1/4" jacks while the ZDT has one 1/4" and one 4-pin XLR jack.  Plugging in two pairs of low impedance phones into either amp did not seem to affect the performance, unlike my Sq Wave XL which used to struggle if one of the two phones was not a high impedance phone.  
 
The ZDT offers an 8-watt speaker output, while the P-1u offers an RCA loop-out instead.  The ZDT 8-watt speaker out is quiet enough to be used to drive another amplifier (according to Craig at EC), but I feel it would be dangerous to try that in real life.  So the P-1u is more useful for someone with two amps where their source only has one output, and its loop-out could be used to feed a speaker amp since it doesn't drive speakers like the ZDT.  The P-1u is more convenient to set up because the PSU is built into the main amp's case, and you don't have to find a place to hide an external PSU box where the umbilical can reach the amplifier like you do with the ZDT.
 
Finally, I wanted to comment on the quality and function of the volume pot.  The P-1u has an extremely precise volume pot for low volume listening using very sensitive low impedance IEM. I could turn the volume down to near inaudible levels and not develop a right or left channel imbalance like with some amps using a lower quality attenuator.  My ZDT and WA6 volume pots come very close to the P-1u in this regard, and the Amphora with it's stepped Gold Point is also balanced at the lowest setting, while the HDP has a noticeable channel imbalance when turning the pot below below 9 o'clock, above where listening levels are sometimes louder than desired for listening to music while falling asleep.
 
IMPRESSIONS:  I unpacked the P-1u and was immediately struck by how solid and hefty it was.  It seems built like a Mac truck, with a classy feel to the case and knobs.  I liked the combination of grey matt case with silver front panel, giving it more contrast.  At first I wasn't sure about the gold accent plate with the Luxman name/logo on it, but it grew on me very quickly.  Normally I don't go for gold accents, but it didn't turn me off in this case (you'll notice the K240M have a gold accent among silver/black theme).
 

 
When I first fired up the Luxman it sounded great right out of the box.  I can't say how much of a difference warm-up makes, but I did make it a habit to do any serious listening after it had been running for at least an hour.  I did the same with my other tube amps as well.  Never during any of the time I used it did the P-1u case become warm.  This is in stark contrast to my ZDT which becomes hot enough to cook an egg!  I can't use the ZDT in my bedroom during the summer because it heats up the room too much, so I use it in my basement where it's always cool year round.  
 
I listened to the P-1u for the first time with the HD800 and Hyperion cable, and my first thought was how similar it sounded to my ZDT and how it replicated the tube amp's sound via solid state.  Over halfway through Nancy Bryan's "neon Angel" in 24/96 hi-res I realized that I had gotten lost in the music and wasn't taking any notes or trying to collect impressions for the review.  That was a good sign, and it happened repeatedly over the next two weeks. The P-1u doesn't seem to have any sound or flavor of it's own, and does not have any qualities to the sound signature that make it an amp that would need to be limited to only certain headphones.  Like my Perfectwave DAC, I found the P-1u to have a very natural, open and transparent sound, which simply made the gear disappear, leaving just the music and whatever sound the headphones would impart. If I had to attribute a character to the sound, I would say it is warm sounding without any hint of darkness to go along with it.
 
BASS:  String bass was snappy, quick and punchy with a nice clean leading edge to the string pluck and no boomy shadow hanging over the music.  It was well defined and crisp, without any signs of "one-note" bass.  The bass impact and "oomph" was noticeably above that of my Nuforce HDP and still a little above my WA6 and Amphora, running pretty much on par with my ZDT's bass in quantity as well as quality.  Bass extension was very good, and the very deep bass line at the beginning of the first song in Bella Sonus "Enamoured" was quite present and not faded out or reduced.  
 
With loud rock or electronic music the bass did not break up and clip until very high levels that I would never listen to normally.  The bass gave a solid foundation to the presence and weight of the instruments, which the WA6 and Amphora strived to achieve but only the P-1u and ZDT could fully attain.  I noticed this with just about all my headphones except my K1000.  While the P-1u could actually attain useable volume levels with K1000, the ZDT still provided slightly more bass impact and volume with those difficult to drive headphones.  I should note that the ZDT itself is still not optimal for driving the K1000, and has never been able to match the Cavalli EHHA or the next step up to my SAC KH1000 amp in driving the K1000 (last October I did an A/B comparison of those 3 amps with K1000).
 
MIDRANGE:  I found the mids to be warm and inviting, vibrant and detailed, and not recessed at all, even with the HE-5 which are not as full sounding as the HE-5 LE.  Texture and tone of natural instruments was rich and clear, where with strings you could hear the vibration of the body of the instrument and not biased towards strings and bow like with the HDP.  Guitars sounded like they were really there, which caught me off guard a couple of times as I looked up to see if my daughter had wandered into the basement with her guitar.  Vocals were handled very well, and I could not ask for better, regardless of female or male vocals.  Like with my ZDT, when listening to a piano I had a better sense of the instrument being there in the room and taking up physical space when listening with the P-1u than with the other amps, although the WA6 and Amphora were better than the HDP in this regard as well.  The mids of the WA6 and Amphora were more forward than the ZDT or P-1u by a small but noticeable degree.
 
TREBLE:  This is the one area where the P-1u pulled slightly ahead of the ZDT in terms of sound.  I found the P-1u treble to sound slightly sweeter and more extended than the ZDT (or WES for that matter), with a more natural ring to cymbals.  I do feel that my Woo WA6 has a similar treble to the Luxman, but the rest of the WA6 sound doesn't hold up as well vs the P-1u. The ZDT and WES both have a similar treble character to each other and seem like they have more energy near 10 Khz than the Luxman, while the P-1u seems like it has more energy past the 10 Khz mark.  This was slightly supported by test tones from Bink Audio Test CD, but my hearing starts to roll off beginning at 12 Khz and is gone after 16 Khz.  Regardless, through the ZDT or WES the sound of the cymbals being hit by the drum stick seemed to be slightly more prominent at the lower treble frequencies than with the P-1u, while the cymbal strikes through the P-1u sounded a little more natural with higher frequency harmonics to my ears.  This was a subtle difference and some people might not hear it right away until it was pointed out, as the P-1u and ZDT sounded quite similar in all other areas.
 
SOUNDSTAGE and DETAIL:  The P-1u soundstage size is wonderful, and on par with the ZDT which sounded as big as the Woo WA22 with a balanced source last summer.  The lack of a balanced output does not seem to hold back the P-1u at all.  Both amps are clearly more spacious, with a deeper soundstage than the WA6 and Amphora which sounded more forward and narrower, although those two still surpassed the Nuforce HDP.  All of these amps have great detail; but air, ambience and space when listening to the P-1u and ZDT stood out above the other amps, as a demonstration of their improved micro-detail, decay and dynamic range.  Imaging was equally as good, and everything had it's place in the soundstage and headstage, without blending or blurring of instruments.  In contrast, with the WA6/Amphora instruments were squeezed closer together, and with the HDP the soundstage was even narrower and compressed in comparison to the others.
 
POWER and DYNAMICS:  The Luxman P-1u is a very powerful headphone amp with the typical headphones, and the gain is set just right for both IEM and full size headphones.  With the PWD DAC RCA output as source I would normally listen to the JH13Pro with the volume at 9 o'clock, at 10 o'clock with HD600/800, and at 11 o'clock with HE-5/5 LE.  With almost all of my headphones I could play the music louder than I would ever want to on the P-1u without clipping or distortion (like with the ZDT), while with the WA6 I could play the HE-5/5 LE at max volume and still fall 4-6 dB below that of the P-1u or ZDT.  The 600 ohm AKG K240M did not present a problem load for the P-1u.  Although I might normally listen with the volume knob closer to 1-2 o'clock, I could turn the volume even higher than I'd like and the amp didn't run out of steam.  It appears that the P-1u has good voltage swing as well as good current handling ability.
 
When listening to live recordings and trying to imagine that I was there at the actual performance, both the P-1u and ZDT offered excellent headroom for dynamic passages, even when the volume was set for higher than normal levels during the quiet parts of the performance.  However, the K1000 needed the P-1u volume to be closer to 3 o'clock, and I could turn the volume to maximum a 5 o'clock with those and it would still not be uncomfortable to listen.  With the K1000 the ZDT seemed to offer an extra 1-2 dB in volume and slightly better bass impact and control, even though the ZDT is also not optimal with the K1000.  Neither amp could give me a satisfactory illusion of "being there" with the K1000 like my SAC KH1000 amp can, and that is not even the best K1000 amp out there.
 

 
SUMMARY:  The Luxman P-1u is a no compromise solid state dynamic headphone amp that is among the best I have ever heard, in my home or at meets.  I don't believe in stereotypes when it comes to headphone amps, such as when it comes to describing SS vs tube sound.  But for others who do, I'll tell you that the P-1u doesn't sound "solid state" at all, if by solid state one thinks of stiff or brittle, harsh, digital, lifeless or cold. But it does have all the speed, linearity, detail and power one would expect from SS.  And it has the warmth and refined euphonic sound that one would expect from a high end tube amp like my ZDT.
 
With my HD800 the P-1u is very slightly better than my ZDT. The sound signature, detail and soundstage on both amps are almost identical, but the treble in the P-1u is a little bit more natural/sweeter and extended sounding.  I have mentioned elsewhere that my Woo WES could use a little more treble extension in comparison to the KGBH SE that I heard at RMAF; so it was interesting to note that the ZDT and WES have a very similar quality of treble, while the P-1u treble reminds more of what I'd heard with the BHSE.  
 
The improvement from the P-1u is not enough to have me entertain selling the ZDT to buy one; but if I didn't already have the ZDT and was looking for a high-end amplifier I'd be more likely to pick the Luxman over the ZDT for many of the reasons I mentioned above, and not just because of the sound (runs cooler, more flexible inputs, loop-out, etc).  If I had a pair of Fostex horn speakers like Blutarsky, or still needed to drive a Stax transformer for my Stax O2, then I might stick to my original choice with the ZDT.
 
ADDENDUM:  I want to add that I know it's not really a fair comparison to put a $449 DAC/Amp combo like the HDP up against a $3000 dedicated amp, but it was helpful in providing a contrast that enhanced the differences and more easily showed what the P-1u does better than the average SS amp.  And while I like the HDP as a backup or bedroom SS amp, it would never fill the role of the Luxman or ZDT in my main rig.  While the HDP wasn't completely embarrassed by the amps costing 2x as much, the Luxman is superior to it in most areas - especially in soundstage or spaciousness, transparency, neutrality and refinement (plus low volume channel balance).  The biggest area where the P-1u excelled over the maxed WA6 and Amphora was in soundstage size and depth, where these single ended amps normally kept up with my balanced Sq Wave XL in that area.  Additionally, the P-1u also held an advantage in treble extension over the Amphora (ignoring the power differences).