The Hookup as a Headphone Amplifier
To evaluate the HPA-1 as a headphone amplifier, I used headphones from Audeze (LCD-X, $1,699), Oppo (PM-1, $1,099), and Audio-Technica (ATH-W1000Z, $699). I used Wireworld RCA cables between a Mytek Brooklyn DAC and the HPA-1 amplifier, stock headphone cables from each pair of headphones, and the HPA-1's stock power cable.
Performance as a Headphone Amplifier
I began with the album Friday Night in San Francisco (Phillips). Luckily this live performance at The Warfield Theatre by guitar virtuosos Al Di Meola, John McLaughlin, and Paco de Lucía was put to tape. Each musician is completely on top of his game. There are few live albums in which the intimacy between performers and crowd is so well developed and conveyed to the listener. Through the HPA-1, I could appreciate this intimacy at a near-religious level. In the song "Short Tales of the Black Forrest," the audience demonstrates its high-level enthusiasm for McLaughlin and Di Meola when breaking into a blues jam, emerging from the Pink Panther theme song.
While the HPA-1 presents each guitar with pinpoint accuracy, clarity, and separation in all of Friday Night in San Francisco songs, this is especially true in "Fantasia Suite," the only track where the musicians play as a trio. The HPA-1 also brought out other intangibles to elevate this one-of-a-kind performance to an elite level: the tapping, pick scraping, and communication between performers are easily heard and make it seem as if you were sitting in the front row on that Friday evening in 1981. In my view, headphone listening is about intimacy, and the HPA-1 is nearly perfect in this regard.
Moving to some late 1970s pop, I put on the second album from The Cars: Candy-O (Elektra, MQA, 24/192). The opening track, "Let's Go," is the album's standout track and still gets played regularly on rock/pop radio stations. Throughout Candy-O, Benjamin Orr's bass sounded deep and never muddy, and David Robinson's drums had the punch and depth associated with the best floorstanding speakers I have heard, especially through the Audeze LCD-X headphones. Guitars had excellent tonality and decay. While the soundstage varied for each pair of headphones--with the Audeze being the widest and most spatial of the three--instrument separation and overall clarity were excellent through all three pairs.
It was during my listening to Candy-O that one of the HPA-1's most noteworthy characteristics began to emerge: no matter which pair of headphones I chose, the HPA-1 could coax maximum performance from them. The HPA-1 showed itself to be a versatile amplifier with any pair of headphones.
Blues legends Eric Clapton and B.B. King collaborated to record Riding with the King (Duck/Reprise, 24/88.2) in 2000, and the result was a double-platinum, Grammy-winning blues album. Through the HPA-1, Clapton and King's acoustic version of Big Bill Broonzy's familiar arrangement of "Key to the Highway" was elegant and highly refined. Acoustic guitars were balanced, and the overall presentation was airy and transparent, with pinpoint instrument placement in and across the soundstage. This included varying degrees of three-dimensionality, depending on which headphone I selected. In King's upbeat and bluesy "Days of Old," the balance between Clapton's solo in the left channel and King's comping and accompaniment in the right channel was so tasty that it expertly drew me in, almost like being in the studio with this duo of blues masters.
I concluded with Soundgarden's Superunknown 20th Anniversary Edition (A&M Records). Superunknown routinely delivers a thick tapestry of sound; on tracks like "Limo Wreck" (guitar harmonics) and "Black Hole Sun" (Leslie speaker), the HPA-1 was always up to the task. Throughout Superunknown, bass was deep, authoritative, and highly punctuated. The bottom end never turned to mush, even with guitars tuned to low-D.
The most fun I had, however, was on "Spoonman," the album's best known and popular track despite its frequently changing time signatures, including the more unusual 7/4 time. In my view, the percussion track gives "Spoonman" its uniqueness. During the bridge, the spoons played by Artis the Spoonman (a California and Seattle street musician) were conveyed crisply and clearly. In addition, the sound of (seemingly) pots and pans, played by drummer Matt Cameron, adds to the song's tapestry of sound. The spatial placement of each instrument was open and un-crowded, giving sense of space over the song's distorted and punchy rhythm track. This was the case in all of the headphones I used.
The Downside as a Headphone Amplifier
The HPA-1 has practically no sonic downside. It equals or outperforms almost all other headphone amplifiers I've heard. At $3,500, however, Pass Labs could include a level meter and remote. With every passing year, I think more about my overall health, and that includes my hearing--so I would especially appreciate having some confirmation of decibel level when sound emanates so closely to my ears. The omission of a remote control is simply a bummer. I enjoy relaxing on the couch and getting into a real listening groove, especially with headphones as comfortable as either the Oppo PM-1s or Audeze LCD-Xs. Having to get off the couch to adjust the volume as I switch between albums or songs on my iPad was a groove killer.
Comparison and Competition
As a preamplifier: I really could not come up with a solid-state preamplifier in the exact price range of the Pass Labs HPA-1 that would be competitive in its performance. Therefore, I'll compare it with two much more expensive line-stages with which I'm very familiar. The Ayre Acoustics K-5XE, which retails for $4,350, has excellent transparency, good dynamics, and relatively far soundstaging abilities. However, it sounds like a typical solid-state device when it comes to timbres/tonality. It sounds somewhat "dry" and washed out in comparison with the HPA-1. The SimAudio Evolution 740P, which retails for $9,000, offers reference-level transparency, easy-to-hear micro-details, and excellent overall dynamics, but I found it to be analytical-sounding and somewhat sterile in its overall presentation. It does not offer the full image density or the overall liquidity, tonality, and colors of live music that I heard with the HPA-1.
As a headphone amplifier: The über-high-end headphone amplifier market is a completely esoteric category where prices are high and unit sales are likely small. Despite this fact, the Pass Labs HPA-1 does have some noteworthy competitors. The King by Audeze retails for $3,995 and is a hybrid tube/Mosfet design. Woo Audo offers an extensive number of headphone amplifiers at prices that range from "comfortable for most mortals" up to $15,000. The WA5-LE is a tube-based design for $3,699. The SimAudio MOON Neo 430HA is a solid-state model that sells for $3,500. Finally, I would be remiss not to mention the HeadAmp Blue Hawaii for $5,000, the AURALiC Taurus MkII for $1,899, and the Cavalli Audio Liquid Lightening 2 for $4,499. There is no doubt that choices in the high-end headphone amplifier market, much like high-end headphones, are growing quickly.
The Pass Labs HPA-1 is the first headphone amplifier/preamplifier that this iconic company has ever produced. As a preamplifier, it outperforms solid-state preamplifiers that cost $5,000 to $10,000 more in its purity of timbres/tonality, its overall liquidity, its image palpability, the air it puts around individual images, and its tremendous soundstage depth and width. Does it exactly equal what great tube-based preamplifiers offer, as I stated at the beginning of this review? Not quite, but it's very close indeed--to the point that I would want it in my system if I were going to use a solid-state line-stage. Like all Pass Labs gear, it is exceptionally well built, it's very handsome in its appearance, and most importantly it performs like a champ across the board. If you can overlook the lack of a remote control and an XLR option, you'll find that it kills in its performance and can compete with any line-stage on the market today, offering a bit of tube magic without the hassle and expense of buying and replacing tubes in the future.
As a headphone amplifier, the HPA-1 is unquestionably a five-star performer. It is hard to imagine a far better performer at any price. The HPA-1 is worthy of being mated with the finest cans available on the market today, such as the Focal Utopia ($3,999), the Audeze LCD-4 (3,995), or the STAX SR-009 ($3,799). But as our listening tests confirmed, the HPA-1 is such a high-quality performer that it coaxes maximum performance from whatever headphones with which you pair it. This is a testament to the HPA-1's overall exceptional performance and versatility. It will draw you in closer to your music and provide a sense of intimacy that is nothing short of addictive and will keep you listening for hours on end.
• Visit the Pass Labs website for more product information.
• Check out our Stereo Preamp and Headphones category pages to read similar reviews.
• Pass Labs INT60 Integrated Amplifier at HomeTheaterReview.com.