Pass HPA-1 Headphone Amplifier Run, Don’t Walk (to your nearest Pass dealer!)

By Jeff Dorgay

Listening to Thomas Dolby’s “Ability to Swing,” the Acoustats in my living room have dramatically increased their ability to swing in every way: these vintage ESLs known for their somewhat loose and flabby bass now stand up and deliver Dolby’s snappy synth bass lines with authority.

The low level resolution that this preamplifier brings forth unearths minute details normally only heard on the TONEAudio reference system costing almost a hundred times more; all three dimensions of the sound field painted now expanded to the point of being psychedelic. In 35 years of listening to the Acoustats, they’ve never sounded this exciting. The slow sax fade in on Traffic’s “The Low Spark of High Heeled Boys” becomes conscious so deliciously, so delicately, as the accompanying instruments fold into the mix, it’s creepy the way these vintage ESLs wrap you up in sound.

But this isn’t Pass’ $38,000 Xs preamplifier; it’s their new HPA-1 headphone amplifier. This thing sounds so damn good twenty minutes out of the box, the thought of plugging a pair of headphones in is frightening, fearing my head will either melt or serious flashbacks will be triggered. So for the next few days, it merely does duty as the anchor of a modest 2-channel system, logging some hours on the listening clock. Before you start griping about the unobtainable price, the HPA-1 retails for $3,500 – hardly unobtainable at all.

Sheer genius

Wile E. Coyote lists himself as “super genius” on his business card, but I can’t think of guys more deserving of this title than Nelson Pass and his crew at Pass Labs. I’ve been buying his designs since his days at Threshold circa 1980, and I’ve never heard one I didn’t love. Not like. Love. Personal bias, maybe, but I keep trying everything else, finding plenty of lovely things, but when I come back to a Pass product, it just feels––or should I say sounds––perfect. So in case you haven’t been reading my reviews for years now, I confess my personal bias here, openly.

The HPA-1 is the brainstorm of the newest addition to the Pass team, Jam Somasundram. Speaking with him on the phone is highly enjoyable and he makes it a point to tell me that he “designed the HPA-1 as a linestage first,” giving it the necessary oomph to drive a power amplifier, so that driving headphones would be no problem. A man of major understatement, this thing is fantastic.

Even if you aren’t a headphone enthusiast, but have been shopping for a linestage in the $15,000 range, consider the HPA-1. (Remember, it’s only $3,500…) If you have a minimalist, yet high performance system and can live with two single-ended inputs and a lone single-ended output to your power amplifier, get your hands on an HPA-1 and spend the rest of the money on your system.

Pairing the HPA-1 with everything in the studio and at home from bare-bones vintage amplifiers up to the Pass Xs300 monoblocks used as the anchor to our main system is a treat. Comparing it to a number of other preamplifiers in the $5,000–$10,000 range, the Pass holds its own or outperforms them in terms of quietness, dynamic range and tonality. Once powered up for a few days, and played for about 100 hours, it opens up further, exhibiting a level of refinement you would expect from a $10k preamplifier. Remember, only two inputs, no remote and one set of outputs. But purely from a sonic standpoint, it is stellar.

From a visual standpoint, it looks like an Xs Pre put in a shrink machine. Its diminutive size is less than half of a standard component, making it great for a compact, yet high performance system, or the perfect desktop headphone amplifier.

Oh yeah, it’s a great headphone amplifier

Pass keeps the minimalist thing going here too. With only a single ¼-inch jack on the front panel, they haven’t addressed the balanced thing, or multiple outputs, merely concentrating on the one way of connecting that most headphones offer. Forget about that; this thing sounds awesome.

The Pass press release mentions that it will easily drive planar phones, and this is instantly confirmed with a quick test drive of HiFiMan, Audeze, and Oppo phones. Even the notoriously tough-to-drive AKG phones pose no threat to the HPA-1.

For those who haven’t had the Pass experience, Nelson Pass has said on more than one occasion, he “likes the sound of tubes, without the hassle,” that is, replacing tubes and the occasional catastrophic failure that can accompany high voltage and high heat. The HPA-1 sounds just like the current crop of Xs gear: refined, dynamic and quiet, with a tonal balance a few molecules to the warm side of neutral. Never a bad thing with today’s current crop of headphones, especially the top of the line Sennheiser phones.

After running through a wide gamut of phones to confirm no rocks in the road, most serious listening was done with the Audeze LCD-2s (current version) and the OPPO PM-1s. While this is a very well-balanced amplifier, its strongest suit is the sheer dynamic range it offers. Much like the Xs300 monoblocks we use daily, this extra dynamic range and grip helps whatever headphones you might have, fully controlling their diaphragm, resulting in quite possibly the most wonderful experience you will have with your current phones. Even my late ’70s vintage Koss Pro4aa’s took on new life with the HPA-1 driving them.

If you’ve ever been in a hifi show room, or trade show where the speaker manufacturer uses a massive power amplifier to drive a small pair of speakers with great result, you know what I’m talking about. It also gives whatever phones you are listening to extra oomph in the bass department. Favorite EDM tracks now really feel weighty, especially with the Audeze phones.

As you might expect, the stereo image produced by this amplifier on a premium pair of headphones is big, bold and exciting. A couple of times I caught myself getting up out of the chair, ready to walk away, thinking that I didn’t even have headphones on.

A $3,500 headphone amp with free preamp or vice versa?

Rather than bore you with audiophile cliché after cliché, let’s break it down. The Pass HPA-1 is on the top tier of the world’s finest headphone amplifiers, regardless of cost, end of story. If you can live with the single-ended functionality and a single output, you’ll have a tough time getting better sound anywhere. It is an expensive headphone amplifier, but delivers the goods. If you are only looking for a headphone amplifier, this is the top of the heap.

As the control center of a minimalist hifi system, it offers performance far beyond what you’d expect to get from a $3,500 linestage, and it has a world-class headphone amplifier thrown in for free. Again, if the topology fits your needs, even the most crazed audiophile could live the rest of their days with the HPA-1. It’s that good. Even if you never plug a pair of phones into the front panel and merely use it as a preamplifier, this is one of the best values in high-end audio today. And swing it does.

The Pass HPA-1