Pass Labs HPA-1 Headphone Amp Review

[LTig]

The measurements are actually quite similar when viewed at 1V out (JA measures at 1V out, Amir at 2V)
Except frequency response and PS noise that is...
For some reason JA measured 60kHz -0.5dB in 100kΩ load, where Amir measured 40kHz @ -0.5dB in 600Ω load (which also isn't bad)

JA found out that the frequency response depends on the setting of the volume knob.

 

[Palladium]

This is further proof that High End Audio needs to re-calibrate their sights and ways... This is the usual poor showing from them... remember the Total Crap ... err.. Dac? $15,000 for less than Apple dongle ($9.95) performance.

That's pretty funny in a context where people are giving JBL a hard time for idle hissing on a $200 pair of 305s.

 

[restorer-john]

JA found out that the frequency response depends on the setting of the volume knob.

For those of us who actually test gear to determine how and why it sounds the way it does, the position (rotation) of traditional volume controls is a huge part of the FR picture.

Sadly, the current ASR cohort (apart from a few outliers) understand what we are talking about. So we don't bother trying to explain it.

 

[Metronomy]

Not enough for what? You can buy a HP amp with excellent performance for low hundreds of €/$/£, and little more even if you include excellent DAC performance.

Not on my part as it has been translated but intended in my nation, Italy.

In fact, in my opinion it is perhaps the bloodiest purchase among the headphone amps

 

[solderdude]

JA found out that the frequency response depends on the setting of the volume knob.

It usually is simply because the circuit behind the volume control has a capacitance so a low-pass filter is created that is frequency dependent.
This thus depends on: volume control position (-6dB is worst case), resistance value of the volume control (the lower the better), input capacitance of the circuit connected to the wiper.
Judging from the PC no extra capacitors on the input so it would only be the input FET GS capacitance and the flat-cable.
Given the fact that gain is only 2.5 x and Amir testing with 2V in and adjusting the volume to be 2V out the volume control would have been near the maximum value so smallest frequency range so in this particular case the volume control would have been close the technically 'worst' condition.

 

[Robbo99999]

JA found out that the frequency response depends on the setting of the volume knob.

lol!

 

[LTig]

lol!

It's not uncommon, if the volume control is directly at the input. The input capacitance of the following stage (including any cables in between) forms a low pass with the resistance in front of it. Its cut frequency is lowest when the slider of the volume pot sits in the middle of the full resistance.

 

[peng]

This Pass did not a pass Amir's scrutiny.

That said. Pass aficionados expect harmonics and higher 2nd than 3rd and no higher harmonics (tube like).
Pass delivered on that and with only slight hints of that distortion.

He is one of those audio electronics designers who actually hold a degree or two in Physics. So no surprising he has the know how to designed in the 2nd and 3rd harmonics that he believes most people may actually like, but suppressed the higher order ones. Amir, obviously is not fond of the "sound signature" influenced by any harmonics lol..

 

[solderdude]

So no surprising he has the know how to designed in the 2nd and 3rd harmonics that he believes most people may actually like,

That's very easy... either use tubes or use FET's with local feedback. No degree in Physics needed
With HD also comes IM.

 

[Billy Budapest]

Doesn't matter. Whose (company) name is on the thing? Whose reputation is at stake?

I think it matters—if someone purchases an amplifier from Pass Labs, they are expecting the amplifier to be designed by Nelson Pass. If it is not, then what’s the point? I wouldn’t say it’s deceptive marketing, but it’s certainly misleading IMHO.

 

[Billy Budapest]

Correct, but it's under the Pass Labs umbrella that products with relatively high distortion are being designed and appreciated.

See my comment above. When people buy equipment from Pass Labs, you can bet they believe their equipment has been designed by Nelson Pass. In this case, that would not be a correct assumption.

 

[LTig]

With HD also comes IM.

That is the major point why I don't want high HD. Even if its only even order, but be come audible it must be so high that IMD suffers, and that is audible.

 

[Billy Budapest]

i looked at the price.... $3,600

and the single board inside and thought.... where's all the goddamn money gone???

charitably is there even $360 worth of parts in there???


also these are like how Tom Clancy novels are still coming out.... he passed about a decade ago


HARD PASSS

I would say that most of the money being charged is simply for the name Nelson Pass. Although in this case, you aren’t even getting that.

 

[peng]

That's very easy... either use tubes or use FET's with local feedback. No degree in Physics needed
With HD also comes IM.

Of course, that's why I just said not surprising, should I edit it to something like "he knows better", so as not to unintentionally offending the many highly competent designers who don't hold an EE or physics degree?

 

[Robbo99999]

It's not uncommon, if the volume control is directly at the input. The input capacitance of the following stage (including any cables in between) forms a low pass with the resistance in front of it. Its cut frequency is lowest when the slider of the volume pot sits in the middle of the full resistance.

I know, I didn't doubt your post, I just lolled at the crazy fact that volume position changes the frequency response! lol! ha!

 

[AudioSceptic]

Could've been if objective measurements were provided decadas ago. Obviously it will never be purely science based as people like to buy to impress others, lifestyle etc etc
But there's also a part of me that thinks that people don't want to get fooled into giving cash for things that aren't really that great.

Measurements were common into the 70s, but subjective reviewing took over. I always thought we should have both.

 

[AudioSceptic]

Not on my part as it has been translated but intended in my nation, Italy.

In fact, in my opinion it is perhaps the bloodiest purchase among the headphone amps

I can usually translate/guess, but "bloodiest" has me baffled. Could you try some other words?

 

[threni]

JA found out that the frequency response depends on the setting of the volume knob.

My guitar does that!

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Maybe that explains the distortion too!

 

[Metronomy]

I can usually translate/guess, but "bloodiest" has me baffled. Could you try some other words?

Ah sorry in Italian it would be a purchase that generates a blood hemorrhage,sanguinoso Note

 

[MediumRare]

To paraphrase an old saying: you can be a high-performer, but but not good looking, or good-looking and not a high-performer, but you can’t be an ugly low-performer.