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Pass Labs X350.5 Stereo Amplifier Sound Quality Tests


I let the Pass Labs X350.5 warm up for about 1 hour and started out my listening session with some vinyl. 

LP:  Miles Davis: Kind Miles.jpgof Blue (180G)

Despite this being a recording from 1959, it is recognized as a benchmark for vinyl even by today’s standards and is the best selling jazz album of all time.  Accompanying Miles are jazz legends such as Bill Evans on piano and John Coltrane on tenor saxophone.  This album is based on modality and was recorded live in the studio with little to no rehearsal making it almost entirely improvisational.   Track #1 “So What” sets the mode for this album, which is just a feel-good laid back experience that is best accompanied by a good glass of red.  Jimmy Cobb’s cymbal brushes were delicate and airy while the back and forth between Miles on trumpet and Coltrane on sax was exhilarating.  It’s hard to believe such an old recording on vinyl had so much dynamic range, seemingly more so than the majority of CD’s recorded today.   The X350.5 was loving pumping the juice to my Status 8T speakers as I turned the volume up to lifelike SPLs.  Closing my eyes, I really felt like I was in a jazz cellar in NYC listening to this sextuplet grace me with their phenomenal performance.  Track #2 “Freddie Freeloader” is my favorite song on the whole album.  It just oozes coolness and if you’re foot isn’t tapping on this tune, someone needs to check your pulse.  Bill Evan tickles the ivories with a surgeon’s precision.  I got instant goose bumps when Miles’ trumpet kicked in.  I just couldn’t get over how lifelike and vivacious it sounded, especially when Coltrane answered Miles in his solo.  I was truly getting that “better than being there” experience found only from properly setting up and pairing the best electronics and loudspeakers in a great sounding room with exceptional source material.  The X350.5 just loved showing off its sonic chops with this album.

LP:  Richard MarxMarx.jpg

I’ve always liked hearing Richard Marx songs on the radio, but never purchased any of his albums because I felt his stuff was a bit too poppy and overplayed.  When my wife bought the LP version of his self titled album, I figured I’d give it a shot.  I was pretty floored not only by the musical content of this LP, but its sound quality.  Side 2 contained songs rarely (if ever) played on the radio and they were much harder hitting than his more well-known radio pop songs. Track #5 “Have Mercy” starts out with some great drumming and a catchy hard rock guitar theme.  This song just rocks and begs to be played loudly.  Richard’s voice came through very vibrantly and the band just sounded excellent together.  This is power rock at its finest and something hard to find today from mainstream music.  Although it sounded a bit edgy at high listening levels, it was never fatiguing or overly bright.  Instead, I felt like I was thrust into a live performance with the music enveloping all around me, despite the fact that I was listening in two-channel.  Track #6 “Remember Manhattan” was a big WOW for me.  I didn’t know vinyl could produce so much bass and certainly not from an album like this.  But here I was with chest pounding bass providing the framework for this awesome song.  Dynamic, bold, lifelike, the X350.5 showed no limits in how hard it could drive my reference speakers, which dip down to 2 ohms at bass frequencies.  If you’re not a Richard Marx fan, I can assure you will be after hearing the entire second side of this album.  Check it out!

SACD: Grover Washington JR – Prime CutsGrover.jpg

I’m not even sure how I acquired a copy of this rare SACD but it’s a sonic masterpiece and a must have in your collection if you’re serious about sound and a jazz aficionado like myself.  Track #1 “Take Five” has a lot of stuff going on at once, including a deeply rich bass track.  Grover’s saxophone came through with pristine clarity while the percussive effects popped out into a very three dimensional landscape.    Track #6 “Summer Nights” bore a similar resemblance to “Pyramid” from another great album called Close Up by David Sanborn.  I loved the ping pong effect of the percussion instruments between the speakers.  The Pass Labs amp was just pumping clean power to my speakers and rewarding me with an unrivaled sonic landscape.  You could hear the triangles slowly decay instead of just sharply fading away, which would otherwise be lost on lesser-designed gear.  The noise floor was dead silent which really helped showcase the dynamic range of this excellent recording. 

SACD/ Blu-ray:  Jienat - Mira

Last month I wrote about Blu-ray:  Jienat - Mirathe sonic wonders this Blu-ray disc posesses.  Well, an SACD copy is also included with purchase so I cued up the two-channel track to give the Pass Labs amp a real workout.   I caution anyone to use the volume control sparingly when playing this disc on their systems as it has extreme dynamic range that most speakers are incapable of reproducing at  reference volume levels.  The vocals were pinned dead center in Track #1 “Sissel” as if I had my center channel engaged.  The bass was thunderous and the stereo separation seemed to extend well beyond the width of the speakers.  Track #6 “Fredrik Albert” showed off the fabulous transient response of the X350.5.  The immediacy of the percussion and depth of the bass was simply spectacular and it’s not something that can fully be conveyed in writing without actually hearing for yourself.  I don’t know the language spoken in this recording (in fact only about 500 people speak this dielect so chances are you won’t understand it either), but somebody must have a really great “uncle” since some incarnation of that word seems to be a constant theme in this song.  I love it!

Even in the two-channel recording of Track #4 “DanceHall”, you’re enveloped in the middle of the room with singers all around you. The percussion was full of life and vibrancy that you rarely ever hear in any recording.  Most playback systems are incapable of reproducing the dynamic range of this album, but the X350.5 did a fabulous job delivering the power necessary for the Status 8T speaker system to accomplish this goal with utter ease.  Towards the end of the recording, the electric bass kicked in which literally blew me away as I was belted with sustained tactile bass that was not only heard but rattled the core of my bones.  This was the first time I saw the current meter jump up and sustain past the half-way mark on the X350.5. The blue led was actually flickering as the amp just sucked current from my 20A wall outlet and fed it virtually unadulterated to my speakers.  While I was unable to instantly compare how the X350.5 sounded to the Classe CT-2300 I also had in for review, I did make some notes.  I found the Classe amp put forth a more laid back presentation while the Pass Labs amp seemed a bit more forward tonally.  Both amps sounded great and were able to drive my speakers with aplomb. But, sonically I couldn’t necessarily declare an absolute winner as much as note there were perceived differences. Depending on source material, I found myself preferring one over the other by a small margin.  I felt the Pass Labs X350.5 was a bit more transparent at revealing subtle nuances while the Classe CT-2300 provided a sometimes smoother and more natural presentation.  For this track however, I was still craving both company’s flagship amplifiers to feed my speakers even more clean power.  My wife says I’m nuts but isn’t that what being an Audioholic is all about?


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Recent Forum Posts:

Rich Davis posts on October 12, 2013 16:33
There a LOT of VERY expensive amps on the market. In terms of how loud they go? Any good amp will probably drive most speakers past what is considered normal listening levels. I don't know if you've done any dB checks, but most of the time I only have my system at around 85 to MAYBE 95 dB on a continual basis. Anything louder than that is not typically good for your ears to have a system operating much louder than that. Most systems playing at that volume level are not using maximum output. Some speakers can handle large amounts or need large amounts of power to drive. Electrostatic, MBL, and other speakers might require or like large amounts of power, but in most cases, you'll probably not use much more than 20 or 50 watts, especially if you do things like bi-amping.

Don't judge a system by how loud it goes, since most of these places won't even turn up the system to maximum levels, because you can't sit within 60 feet of the speakers when they drive them to maximum spl. I have a pair of Meridian DSP5500s for mains, a DSP5000 center channel, with some other DevTech rears and a Talon sub and I can't sit in the same room after I turn up the volume knob past a certain point. Listening to a system in the 100+dB range is just not something good for your ears. When you go to a concert, break out your smartphone and a dB meter app and see what the dB is at your listening position.

Go to these sites and check out some of the most insane systems available. HigherFi - Worlds Best HiFi High-End Speakers and Audio or HIGH-END PALACE - The place for the world's best music systems!

And $50K for a pair of monoblocks isn't the high end, it's not more mid high end in terms of price. one can spend upwards of $500K for the Pivetta Opera or $200K for the Goldmund Telos 5000's, etc. so $50K for a pair of Pass is pretty cheap. :-)
Rich Davis posts on October 12, 2013 16:23
Pass makes nice stuff

Personally, when it comes to power amps, there are so many good amps out there and it's all a matter of matching up with the pre amp, cables, and speakers to achieve the desired end result.
Irvrobinson posts on October 26, 2012 23:21
surveyor, post: 917475
In the fact that it's more powerful than either the Mark Levinson or the ATI amps says it all- it truly a beast!

Actually, both the Levinson and the X350.5 are both merely in the middle of the respective manufacturers' product lines. If you want to get really silly with amplifiers both companies will fully accommodate you. Pass makes an X1000.5, and Levinson makes the completely ridiculous No53 monoblocks for $50K per pair. The Pass Labs monster is a comparative bargain at only about $35K per pair.
surveyor posts on October 26, 2012 22:00
gene, post: 917055
Yep an amp spends most of its time operating at low power so it's good to see how quite and clean it is there.

No doubt the ATI amp is a good one but it's not as powerful as the Pass Labs.

Using square waves to test an amp has little value these days when you can power sweep from 10-20kHz and beyond with modern test equipment.

The Pass Lab's amp displayed extreme linearity at all power levels for the entire audio band.

In the fact that it's more powerfull than either the Mark Levinson or the ATI amps says it all- it truly a beast!
craig7 posts on October 26, 2012 21:37
wow you guys reviewed a product ive actually seen in person before
and yeah… it is a pretty beast amp. ive never heard any system louder than it… it was incredible
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