Pass Labs HPA-1 Headphone Amp Review

[Purité Audio]

You see, with all these $100 devices that measure phenomenally well, but sound like crap.... this site will slowly get to a point where.... there will be no point to measure anything anymore. Of course, there will be $50 devices in a year that will measure better than the current $100 device... but people will lose interest. What's the point? Who cares... at that price point the subjective vs objective would lose any meaning.

What will remain is going to be the question: despite the phenomenal measurements that Amir is showing here, why does this still sound like crap...

So reasonably priced fine measuring equipment sounds like crap does expensive fine measuring equipment also sound like crap?
Does crappy measuring expensive equipment ( see thread title) sound good?
What about crappy measuring inexpensive equipment?
Keith

 

[Extreme_Boky]

As long as your Audio Precision is happy - who cares.

 

[Drakkar Noir]

As the owner of the amp being discussed here, I was really happy with the amp in general. As to the way Amir received it, my guess UPS will have to answer for this after the guys at Pass Labs take a look at it. Because of the review, by buyer backed out; so will either find a different buyer or simply keep it.

As I've stated before, my only gripes about the amp are the felt feet and possibly the headphone jack. In the sound department, measurements is not my top concern.

 

[Hart]

So much of our hobby is a big name, hubris, and follows up by junk. PT Barnum business plan. They should be ashamed. I can't remember how many reviews I have read for Carver/Sunfire products that were absolutely glowing. They were ironically also big advertisers in said magazines. The amps test terribly, the current tube amps are abysmal. Etc.

 

[fpitas]

You see, with all these $100 devices that measure phenomenally well, but sound like crap.... this site will slowly get to a point where.... there will be no point to measure anything anymore. Of course, there will be $50 devices in a year that will measure better than the current $100 device... but people will lose interest. What's the point? Who cares... at that price point the subjective vs objective would lose any meaning.

What will remain is going to be the question: despite the phenomenal measurements that Amir is showing here, why does this still sound like crap...

Wait...what? Forget the wink emoji?

 

[Geert]

Amir received it, my guess UPS will have to answer for this after the guys at Pass Labs take a look at it.

You mean you're going to send it to Pass Labs for inspection?

 

[Drakkar Noir]

You mean you're going to send it to Pass Labs for inspection?

already sent.

 

[Drakkar Noir]

I am actually happy for @amirm 's success and influence as a reviewer, an equally happy that some of the big players like the one @WayneC represents here are taking notice in this trend. Should not be so difficult for a company like Pass Labs to change a screw, connector or wire here and there to make their products more competitive in the measurements department. We all stand to benefit from this.

I for one know PS Audio and Schiit are currently releasing new and updated products that they claim measure well, no doubt because of reviews on forums like this one.

Sucks that amongst the useful information provided here there are those that are only too happy to pile on the bashing of some imperfect component for no good reason. You know who you are.

 

[GPJ]

already sent.

Hopefully they send it back to Amir for a retest.

 

[HiFiBob]

The HPA-1 isn't junk. It's a well-engineered and solidly built product that doesn't have "ultralow distortion" on the Marketing Requirements Definition spec sheet. I don't think it's accurate to invoke P. T. Barnum. Changing a screw, connector, or wire here and there isn't needed and won't improve measured performance. Pass Labs built the amp this way for specific reasons. Whether you agree with those reasons is a separate question.

I could post the reverse-engineered schematic from diyaudio.com sometime and go through some of the design details and rationale. Probably not since most people won't care. There's a few things about the circuit I disagree with. I know from the diyaudio discussion that Jam feels any changes to "improve" performance would detract from the sound. That's a personal subjective opinion and I can't argue with it.

For instance, the unbuffered front end is heavily loaded by two resistors which set the overall open-loop gain to a low value, giving IIRC about 18dB NFB. That could easily be changed to give more feedback but then it would be a different design. It's not bad engineering, just a conscious decision on Jam's part.

About the only thing I think is really wrong with the amp is the design of the output stage bias spreader circuit. The way it's implemented, the amp takes a long time for the output stage idle current to settle down. This could have been done better, IMHO, and would probably do away with the always-on recommendation. Electrolytic capacitors only have a few thousand hours operational lifespan, so you can easily wear them out in a few years if you never turn the amp off.

There are a few other compromises which I think have to do with the parts that were available in the Pass Labs stock room. Overall, I think it's a pretty elegant circuit.

 

[HiFiBob]

By the way, I didn't come here to cheerlead for the HPA-1. I think it's a nice-sounding amp, but to my tin ears not the magical experience you'd expect given all the hype and breathless subjective reviews. I just happen to have sentimental feelings about discrete transistors that have nothing to do with sound quality. The HPA-1 does sound a little different from other amps. There may be people with more refined hearing than me who legitimately appreciate that difference, or maybe they just have their own sentimental attachments to the thing. It's not my place to question their preferences.

I would say it's equally misleading to market an amp as "better" because it has 101dB SINAD versus 97dB. That's just nonsense. I keep wondering what the point is of ranking components in order of inaudible spec differences.

But I really don't want to argue. Fighting is so tedious.

 

[Drakkar Noir]

The HPA-1 isn't junk. It's a well-engineered and solidly built product that doesn't have "ultralow distortion" on the Marketing Requirements Definition spec sheet. I don't think it's accurate to invoke P. T. Barnum. Changing a screw, connector, or wire here and there isn't needed and won't improve measured performance. Pass Labs built the amp this way for specific reasons. Whether you agree with those reasons is a separate question.

I could post the reverse-engineered schematic from diyaudio.com sometime and go through some of the design details and rationale. Probably not since most people won't care. There's a few things about the circuit I disagree with. I know from the diyaudio discussion that Jam feels any changes to "improve" performance would detract from the sound. That's a personal subjective opinion and I can't argue with it.

For instance, the unbuffered front end is heavily loaded by two resistors which set the overall open-loop gain to a low value, giving IIRC about 18dB NFB. That could easily be changed to give more feedback but then it would be a different design. It's not bad engineering, just a conscious decision on Jam's part.

About the only thing I think is really wrong with the amp is the design of the output stage bias spreader circuit. The way it's implemented, the amp takes a long time for the output stage idle current to settle down. This could have been done better, IMHO, and would probably do away with the always-on recommendation. Electrolytic capacitors only have a few thousand hours operational lifespan, so you can easily wear them out in a few years if you never turn the amp off.

There are a few other compromises which I think have to do with the parts that were available in the Pass Labs stock room. Overall, I think it's a pretty elegant circuit.

My comment about improving measured performance is more about it being not so difficult to obtain, IF you wish to go that route. I mean, some of the more recent brands are achieving this constantly and with what I assume are limited funds. I'm sure Pass Labs is able to afford the best measuring equipment.

As I've stated before, to me this makes very little difference. I listen to mostly rock music and my favorite headphones with the Pass are the very euphonic Audeze LCD-3 and Grado RS1, so yeah. These headphones make Pearl Jam sound even more like Pearl Jam. Doesn't matter to me if I can't listen to Eddie Vedder's nose hairs move with this setup. That's what it all comes down to, isn't it? better performance would mean better detail retrieval. To me the Pass is good enough, great even.

If there is any sloppiness in the build or mishandling during shipping to Amir, Pass will hopefully fix this.

 

[oleg87]

For my money, measurebating over astronomical SINAD ratios far beyond human hearing is far more irrational than chasing whatever "euphonic" colorations get subjectivists going.

Unless you're looking for something that doubles as a low-cost lab instrument, transparent, low-cost headphone amps of moderate power levels are a solved problem. No value Pass or any company that can't fab high-performance op-amps can add there.... feature set, that's a different discussion.

 

[DonR]

For my money, measurebating over astronomical SINAD ratios far beyond human hearing is far more irrational than chasing whatever "euphonic" colorations get subjectivists going.

Unless you're looking for something that doubles as a low-cost lab instrument, transparent, low-cost headphone amps of moderate power levels are a solved problem. No value Pass or any company that can't fab high-performance op-amps can add there.... feature set, that's a different discussion.

Ditto for DACs. Once the audibility threshold is passed, the price becomes a sticking point for me particularly if there is no other objective or subjective embellishments.

 

[Xulonn]

As I've stated before, to me this makes very little difference. I listen to mostly rock music and my favorite headphones with the Pass are the very euphonic Audeze LCD-3 and Grado RS1, so yeah. These headphones make Pearl Jam sound even more like Pearl Jam.

Wow! So you are saying that these headphones and the Pass amplifier produce a sound signature that accurately duplicates rock concert venue PA systems?

That's quite an accomplishment!

/s

 

[Drakkar Noir]

NO. I'm saying I find rock n roll very pleasing and exiting with this setup. Very simple.

 

[amirm]

For my money, measurebating over astronomical SINAD ratios far beyond human hearing is far more irrational than chasing whatever "euphonic" colorations get subjectivists going.

There is a time to make that argument, and there is a time not to. SINAD at high values indicates noise floor. With headphone amps and sensitive IEMs, noise level matters hugely. Another thing that is king is amount of power. Without that, you are going to distort and in anything but "euphonic" way. Given this massive box and heavy weight, there is no reason to not have more power than this box outputs. These are the things that damn the product, not the pure distortion story.

Here is again the power story:

My *minimum* bar for power at 300 ohm is 100 milliwatts. Desktop products go way past this routinely including this little $109 box from Schiit:

That is 3X more power. This is hardcore, reliable, objective data that directly translates into subjective listening.

So please park the talking points at the door. This box is simply without a market in high-end or even middle of the headphone market. Folks routinely buy insensitive headphones these days and need a clean, noise-free, powerful source to drive them.

 

[amirm]

I appreciate that Nelson Pass employs American workers and provides them health insurance and benefits. You can build your own HPA-1 clone. Good luck making it the same quality for under a thousand dollars, and that doesn't account for the costs of labor, marketing, customer support, and keeping the factory lights on.

So that is how it works? My $3,000 spent on something other than this box like college education for kids, a vacation, etc. would not support American labor but this box does? And what about the fact that there are at least three American companies with products that cost a fraction of this with better performance? Money spent with Schiit and JDS Labs doesn't count? But spending thousands on this box does? Good grief.

 

[amirm]

I've read all the reviews of the HPA-1. They're all very positive, except Amir's.

How many negative reviews do those people post? Close if not zero, isn't that right? Pass could take a brick, glue RCA connectors on it and these guys would rave about it! This is the power of branding and non-critical evaluation of audio masquerading as "review." This review is reason enough to stop reading those reviews, not second guessing mine.

Remember, I have tested more headphone amps than all of those people combined. The count is easily in hundreds. I actually own probably 50 to 100 one right now! I not only measure each one, I listen to each one using proven, critical methodology that brings out weaknesses of them. I don't just listen to some random new album with each review. This is why all up, I only give thumbs up to only 1/3 of all devices I test:

I suggest waking up and not going by non-critical tests conducted by these "reviewers" and yourself for that matter. I push products to the limit to find their weaknesses. That you or others think everything sounds great is neither here, nor there. You don't have the measurements I have, and comparative data to demonstrate your opinion is valid.

 

[amirm]

It legit makes me sad to see people hating on this amp, and I'm not even a Pass fanboi. I do get tired reading about cookie-cutter Chinese gear all the time. Pass Labs' design philosophy is different. It's a big world, full of injustice. There are plenty of more important things to lose sleep over. IMHO and YMMV.

The "philosophy" is to give you a big shiny box with way too little performance -- both objectively and subjectively. If this was a glass vase, sure, you would just look at it. But it is not. While many including myself value looks as well, high-fidelity and limitless performance has to come at these prices. I should not be able to plug in a headphone, crank up the volume and have it distort. What on earth am I paying for if it is not for avoidance of that? My amplifiers driving my speakers are insanely expensive. But they output 1000 watts into 4 ohm. That is the limitless power I need to drive my speakers. So when someone asks me why I bought them, I can point to a reason. That reason doesn't exist here.

To be sure, I am not here to judge whether any product should or should not be in the market. You all do. I present data and provide metrics that show the limits of the product and tell its true story. And that story says you are paying for metal and not performance here. And in audio, performance better be priority #1 or you are in the wrong hobby.