Pass Labs HPA-1

I'll take a stab. I've owned a HPA-1 for over 3 years and it's been my daily driver the whole time. I mostly listen to planars but do own a pair of HD600's; I've mostly been listening lately to the HE-1000se and Meze Liric II. I don't like the Focal sound... I find it hard like rebar. So that's kinda where I'm coming from taste-wise. I also prefer MOSFETs to BJTs, I like that they have more bite.

It is not the most resolving amp out there, but it's more resolving than most. People who say they want the most resolving whatever are often surprised how shitty most recordings are, and want back into the Matrix lol. It has an even tonality, though it might sound slightly light (it's class A with little overall feedback) until you listen to something bass heavy - it's got cajones. For me at least, the imaging extends outside my head but I'm sure there's better out there.

I wouldn't call it forgiving, if something sounds like shit the HPA-1 won't fix that. I would call it non-fatiguing and enjoyable to listen to. It's kinda the opposite of a THX-AAA based amp, which I find to be a real slog to listen to. If you read what John Atkinson and Gary Katz had to say over at Stereophile/Innerfidelity, they pretty much cover it from two very different angles. No need for me to write 3k words saying pretty much what they said.

I'm obviously a bit biased since I've felt no need to upgrade my headphone amp; but other than only having a 1/4" jack and RCA in/outputs I find nothing lacking. It gets out of the way of the music so you can just enjoy it, which is what I want in my gear. If you're curious (and patient), they come up used regularly so you can snag one and give it a thorough listen for very little risk.

Hope that was at least a little helpful.

 

@Supamark, incredibly helpful. Thank you for sharing your long-term impressions. I love that you've found it non-fatiguing and enjoyable to listen to. Over the years I've noticed a general trend among some on SBAF to prefer amps that seem to have lots of dynamics and transient edge. Ragnarok 1.5 comes to mind in that respect. I found it torture to use with the Utopia and HD600, but decent with the HD650. Similarly, when I had a Torpedo 3, I initially had the older build with the Edcor transformers, no CCS, and default caps (not the Mundorfs). I really enjoyed that amp with both the Utopia and HD600 (moreso with these), but after the upgrades I got rid of it because it sounded too aggressive for me. I expected to find the 3FN too aggressive as well, but surprisingly have not. I just think it could use a slightly better DAC match than my current Yggdrasil Analog 2.

By triangulating impressions and my own experience with the 3FN, it seems the HPA-1 would offer less resolution, more noise, and less air at the tippy top of the audible frequency range, but I may just need to compare myself to find out how that shakes out in practice. Especially with more of the intangibles like tonal density, weight, timbre, etc. The 3FN is the best I've heard in that regard. A consistent theme I saw across the ASR and Stereophile reviews of the HPA-1 is that the amp isn't the quietest due to some power supply noise. I wonder if the Utopia would pick up any of that noise or hum given its sensitivity. I had a similar issue using that headphone with the Eddie Current Black Widow 2 some years back, but have absolutely zero of that with the DSHA-3FN. The cost of the HPA-1 is also absurd, even 8-9 years after release, though it seems that deals can likely be had from time to time.

Have you spent much time comparing different DACs with it to tweak the sound of the chain with the HPA-1 to your liking? I note you mention a Brooklyn DAC in your profile, which appears to use an ESS Sabre 9018 chip.

 

First, let me say it's Bob Katz, not Gary (unrelated afaik) who did the Innerfidelity review. Bob is a Grammy winning mastering engineer, Gary produced Steely Dan. Both pretty cool accomplishments in music. I get them mixed up often. Also, thank you and you're welcome.

I haven't used a lot of DACs with the amp, but I already had DAC preferences before I bought it. I use the Mytek for two reasons; first it has filter selections (I prefer min phase, slow rolloff), and second it has word clock input which is handy in pro situations and it sounds fine. The HPA-1 is resolving enough to tell the filters apart without much brainwork. I have also used the Gungnir Multibit A2 with the HPA-1, and it sounded as bad to me as it usually does lol - I really detest linear phase brickwall filters (especially Schiit's), not a fan of min phase brickwalls either. I've used it with my Holo Audio May (KTE) via the tape outputs on my Pass XP-22 preamp (I like the Pass house sound, so keep that in mind vis-a-vis my opinions) and it sounded great to me. Holo's filter is a different kind of awful lol, hence the hqplayer rabbit hole.

The noise floor is fine, it doesn't use global negative feedback so it's a bit noisier than avg but the tradeoff (to me) is way better transient response and resolution. Fun fact, the best mic's only have like an 80 to 85 dB s/n... so the s/n of pretty much every recording ever is worse. I had a THX-AAA based amp in for a review (it made me quit reviewing lol) and its' s/n was so legit low I could hear the driver cone distortion of the HD600; like tiny little saw teeth. It uses a metric fuckton of feedback, and sounds awful (but punchy!).

The HPA-1 has plenty of "air" unless you mean like a Focal speaker, which sound whispy to me. You could almost say it's an ultra refined Schiit Asgard 2 on high gain, which is also class A no feedback. Far less noisy, far more detail and refinement, with a much blacker background. And way mo' power. I will say where it's lacking a little bit is in drive; like "Trip Like I Do" from Crystal Method's Vegas doesn't pulse quite as forcefully as it should.

You could listen to Lyle Lovett's "Joshua Judges Ruth" - the HPA-1 sounds a lot like that album. It was produced and engineered by George Massenberg, using a lot of gear he designed (he and a few other guys invented the parametric EQ, so he knows things). The versions on Qobuz/Tidal sound pretty much like the CD. His gear has a sound, it's not unlike the Pass house sound, and it's all over that album. It's also just a really good album. If you don't like that album's sound, you probably won't like the HPA-1.

I am not familiar with the headphone amps you listed (there's a bazillion of 'em out there), nor the DACs though I suspect the Gungnir Multibit doesn't sound too different than the Yggdrasil since that Schiit filter is what it is. Some of that aggression may be your Yggdrasil and its' filter, but lots of people love 'em so ¯\_(ツ)_/¯. You may have also, with the Torpedo 3, liked the sound of the transformer by your description. They all (transformers) roll off and smooth the high end to varying degrees and give some low mid boost. If that's the case the HPA-1 may not be what you're looking for.

The only comment I have on the pricing is that it's cheaper than a lot of TOTL headphones, and is refective of the cost to make, service, and sell it through a middleman (dealer). If you're unfamiliar with Pass gear, it's the least expensive way to get a good taste of their house sound. I think they go for about $2,500 used.

 

Update upon new (to me) DAC in my headphone chain.

I just upgraded from a used Brooklyn DAC+ to a used Mytek Manhatten II, and the difference in force and drive is remarkable. The chip goes from an ESS 9028 to a 9038, but I think the big difference is a big ol' linear power supply instead of a switcher - it weighs 4x as much! Probably a better output too. The HPA-1 will play with a great deal of force if it's in the signal. A very interesting and educational experience to me. We'll see if the love affair lasts, but so far I'm really diggin' the Manhatten II + HPA-1.