Against the AMP-23R, the HPA-1c as headphone amp communicated its core virtues even more convincingly than against the DFP. That didn't come as a surprise given Enleum's inherently quicksilvery, highly detailed, elastic and radiant nature as essentially a profile that sits on the opposite end of the spectrum. With Susvara Unveiled, the Enleum delivered feistier, tighter and more authoritative bass paired with a somewhat leaner midrange, more specific image outlines and a shinier slightly more extended treble. Although these headphones aren't quite as demanding as their predecessor, the HPA-1c's volume knob still had to hit about 80% to achieve satisfying SPL. Once there I was genuinely impressed. The Pass didn't hit quite as hard in the low end as the Enleum but to expect otherwise would be unfair. The Susvara Unveiled may crave less power than the original Susvara yet still soaks it up. While most listeners would have agreed that the Enleum was the better companion, the Pass brilliantly showed off their tonally packed, remarkably detailed, liquid, spatially sorted and complex profile. The pairing invited very long sessions without any fatigue. The HPA-1c neither felt threatened by the AMP-23R's extreme resolution nor by its off-the-charts dynamic potency. Instead it did its own thing to a very high standard.
As inefficient as they are, Susvara Unveiled was ultimately better suited to the more powerful Enleum. It was time to level the field with an easier load, Campfire Audio's Cascade. With their 100dB efficiency, the Pass had its sweet revenge. The Cascade's V-shaped tuning emphasizes both ends of the spectrum: bold slightly bloomy bass and crisp highs with a recessed midrange in-between. With the Enleum they sounded spicier, twitchier, more radiant and ethereal but also stiffer and less saturated. The Pass delivered its trademark warmth, full-bodied tone, delicate detail and inviting atmospheric presentation. Most importantly, with the Campfires both amps proved equally fast and supple, rendering the Enleum's earlier advantages irrelevant. Now the Pass struck me as the more synergistic match and I imagine that most listeners would find this pairing more balanced and better suited to the long haul. Also worth noting is that with the Campfires, the Pass ran quieter in terms of background noise.
To explore this further, I paired it with the 5-driver VE5 IEM which boasts 122dB efficiency. Although using such sensitive in-ears with a desktop amp is neither practical nor common, I wanted to hear how much hiss the VE5s would reveal with the Pass: nada. At least my ears couldn't detect any residual hum, only enveloping blackness. For a desktop amp this was a remarkable feat and true testament to a vanishingly low noise floor. Lastly, the VE5s were designed for outdoor use with battery-powered gear, much of which proved far noisier with these IEM than the Pass. Go figure.
Eight years ago I praised the Pass Labs HPA-1 as one of the finest headphone amplifiers I had encountered at the time; and an exceptional preamp to boot. In fact, had I been looking for the latter utility for my desktop back then, I would have seriously considered it in that role alone. Fast forward to today. My hardware, tastes and reviewer experience have evolved yet the HPA-1c impressed me every bit as much as its predecessor did in 2017. Yes it remains a minimalist single-ended design without remote control but to me that hardly matters given what it delivers in turn. Artfully voiced, built like a tank and sensibly priced for its pedigree, the Pass Labs HPA-1c is a must-audition for anyone seeking an exceptional and thoroughly dependable preamp/headfi companion which reminds us exactly why we fell in love with this wonderfully eccentric audio hobby in the first place.
