[jsiau]

Really?
Maybe for the first few hours the sound was unremarkable - though nothing obnoxious, clean but restrained. In less than 10 hours I thought it was handily better than the Bryston BHA-1.
I left it off overnight and I'm only just into day 2 listening and think it sounds awesome. The 'speed', impact, dynamics and textural clarity/detail is killer with the Utopia.
Enthralling on the jazz program I'm listening to at the moment.
Each to his/her own, but personally I can't imagine people returning this thing after they sample the sound - and that's before the unique flexibility and features are taken into account.

My personal take on this is that the "break-in period" is the time needed for ear training.

There is no physical explanation for an electronic burn-in period for the HPA4. Unlike a tube amplifier, its characteristics do no change with operating hours or operating temperature. Our demonstration HPA4 units have many hours on them and they sound just like the new ones coming off the line. They also measure identically.

The total absence of any audible electronic distortion may be a bit unfamiliar at first. This is especially true when driving low distortion headphones. The HPA4 may sound quite different than your old headphone amplifier. Unlike most other headphone amplifiers, it produces no audible distortion. By this I mean that the THD and IMD distortion products will be reproduced at levels that are well below the threshold of hearing. In most other amplifiers, the distortion products exceed the threshold of hearing when playing music at normal listening levels. We are normally unaware of this electronic distortion until it is eliminated. The complete elimination of audible electronic distortion in the playback chain doesn't sound right at first because it is not what we are accustomed to hearing.

Familiar recordings may sound slightly different without the coloration of electronic distortion. This lack of distortion is usually perceived as a slight difference in tonal balance. The clean and transparent delivery may reveal new details in your favorite recordings while delivering a more natural presentation of musical instruments. After spending some time with the amplifier rediscovering familiar recordings, it may be hard to go back to your prior headphone amplifier.

Your ears need a break-in period. Once your ears are broken in, you are spoiled for life.

 

[Tobes]

My personal take on this is that the "break-in period" is the time needed for ear training.

There is no physical explanation for an electronic burn-in period for the HPA4. Unlike a tube amplifier, its characteristics do no change with operating hours or operating temperature. Our demonstration HPA4 units have many hours on them and they sound just like the new ones coming off the line. They also measure identically.

The total absence of any audible electronic distortion may be a bit unfamiliar at first. This is especially true when driving low distortion headphones. The HPA4 may sound quite different than your old headphone amplifier. Unlike most other headphone amplifiers, it produces no audible distortion. By this I mean that the THD and IMD distortion products will be reproduced at levels that are well below the threshold of hearing. In most other amplifiers, the distortion products exceed the threshold of hearing when playing music at normal listening levels. We are normally unaware of this electronic distortion until it is eliminated. The complete elimination of audible electronic distortion in the playback chain doesn't sound right at first because it is not what we are accustomed to hearing.

Familiar recordings may sound slightly different without the coloration of electronic distortion. This lack of distortion is usually perceived as a slight difference in tonal balance. The clean and transparent delivery may reveal new details in your favorite recordings while delivering a more natural presentation of musical instruments. After spending some time with the amplifier rediscovering familiar recordings, it may be hard to go back to your prior headphone amplifier.

Your ears need a break-in period. Once your ears are broken in, you are spoiled for life.

John, I wondered about this myself as I suspected measurements would not corroborate any 'burn-in'.

Indeed from the start the HPA4 sounded not that dissimilar to my Bryston headphone amp, which itself is a pretty low distortion device.
Nonetheless over a period of hours I began to notice differences e.g. a particular (exquisite) purity to high frequency sounds like chimes, increased tonal 'rightness' to difficult to reproduce instruments like piano, increased perception of instrument decay and ambiance in general, greater apparent transient 'quickness', better layering and separation as well as the ability to focus more easily on particular instruments, and perhaps more importantly an ease to the sound in general - that I'm tempted to call smoothness except some might take this to mean 'smoothed over', which is the opposite of how the HPA4 sounds.
I would agree that it takes the ear time to acclimatise and notice these differences, not to mention that different program material will demonstrate the differences to varying degrees.
Perhaps for someone coming from an amp with more overt sound characteristics the acclimation would be more lengthy, if indeed it happens, as I'm guessing not everyone will favour the truth to source sound of the Benchmark.

 

[jsiau]

John, I wondered about this myself as I suspected measurements would not corroborate any 'burn-in'.

Indeed from the start the HPA4 sounded not that dissimilar to my Bryston headphone amp, which itself is a pretty low distortion device.
Nonetheless over a period of hours I began to notice differences e.g. a particular (exquisite) purity to high frequency sounds like chimes, increased tonal 'rightness' to difficult to reproduce instruments like piano, increased perception of instrument decay and ambiance in general, greater apparent transient 'quickness', better layering and separation as well as the ability to focus more easily on particular instruments, and perhaps more importantly an ease to the sound in general - that I'm tempted to call smoothness except some might take this to mean 'smoothed over', which is the opposite of how the HPA4 sounds.

You nailed it! Piano, chimes and reverb tails are where you will hear the differences. The sound of a piano is not right if it is contaminated with harmonic distortion. The overtones produced by a piano are sightly in-harmonic and they beat with the exact integer-ratio harmonics produced by electronics. This makes it very hard to achieve a realistic piano sound through an electronic system. Harmonic distortion must be very low.

Small amounts of harmonic distortion will change the sound of the piano. The same is true for chimes. In contrast, guitars can usually tolerate much higher levels of harmonic distortion before the guitar ceases to sound like a guitar.

Reverb tails can get lost if the bass is delayed due to phase shifts caused by a lack of low-frequency extension. The HPA4 frequency response extends down to 0.1 Hz and this keeps the phase response accurate at 20 Hz. Most amplifiers deliver the bass with a slight delay. A few degrees at 20 Hz may not seem like a problem until you do the math. 5 degrees at 20 Hz is about 2 cycles at 3 kHz or about 7 cycles at 10 kHz.

 

[NEXTLEVEL5]

All i know is I am so glad that I purchased an AHB2 amp with the HPA4 utilizing the Yggdrasil DAC as source and I can now control my bookshelf speakers through the HPA4 when needed. Kudos to Benchmark. Very pleased with the combo.

 

[slc0z]

I have heard the HPA4 at last, so I will add my opinions to this thread.

My existing setup is HD800S (balanced, Cardas Clear cables) driven by
Sennheiser's HDVA600 amplifier from a dCS Puccini source (balanced outputs).
The Puccini also drives my power amp (for the loudspeakers) directly, from its
separatelly buffered single ended outputs.

The possible dual role of an HPA4 as a headphone amp and pre-amp in my system
is obvious.

I've had the Sennheiser pair for years (and the HD800 before the HD800S), so
I'm very familiar with the sound. Although my system had been switched off for
a couple of weeks before the HPA4 arrived I had no doubt that I'd be able to
easily distinguish any differences if they existed. This proved to be true.

I connected the HPA4 (balanced inputs) to the Puccini, with the output level
increased from the usual 2V to 6V (it is switchable). I let the system run for
over an hour to warm up. This is what I heard, relative to the HDVA600: clearer,
tighter, bass that seems of higher resolution. This gives music - jazz and rock particularly -
a more rhythmic and involving feel. The midrange and treble were more detailed and
better resolved. But this is not at the cost of brightness. In fact the opposite is
true. The effects of the well known treble peak of the HD800S (which is better than the
HD800, but still has the same character) were slightly lessened. The HPA4 is not a bright
amp. One of the things that impressed me most was that complex and loud passages did
not become congested or fatiguing - it was still possible to listen "into" them and
resolve the details. In this it is superior to the HDVA600.

For listening through my speakers I had to use the single ended outputs of the
HPA4, because I didn't have the extra balanced cables and I also have some reasons
to believe the balanced input on my power amp isn't particularly well implemented. I
won't go into that here. The sensitivity of the power amp is quite high - 31 dB of
gain - which is not what Benchmark recommend or really design for, as I understand
it. Before listening I turned the Puccini output down to 2 V.

The first thing to say is that I listen to music through speakers less than on headphones,
and only bought the speakers (Monitor Audio pl200 II) this year, so I am less
confident of my judgements of the HPA4 as a pre-amp in my system. This is what I found:
the first thing I noticed was that the improved bass quality I had heard via the 'phones
seemed to have carried over to the speakers. A definite plus. Good. However, there was
a difference in the presentation of midrange and treble that differed from the direct
Puccini->power amp connection in ways I struggled to get to grips with (despite numerous
comparisons). Thinking about it now, I am still uncertain about what I heard. Using
the HPA4, sound was more "controlled" somehow, but perhaps also a bit "flatter" in
presentation (in a rear to front sense) and with a slight lack of top end "air". But
at the same time I wouldn't say, at least not with complete confidence, it was any
less resolving than the direct connection. It remains a puzzle.

The above is as far as I got. I would have persevered, but I had the unit from a dealer on a
sale or return basis. When I realised I probably wouldn't buy the HPA4 because
I wasn't completely happy with it in *both* roles in my system, I felt I ought
to return it. If I was ready to spend 3000 GBP on a headphone amp only, then
I'd buy the HPA4 without hesitation. As a pre-amp, I can only say I'd be very interested
in trying it again in the future, perhaps after a change of power amp and with balanced connections.

 

[townes]

Some years ago, I owned a Headamp GS-X mk2. I sold it, because:
a) its form-factor. It needed too much space. The cable between its power supply and the actual amp is rather huge and hardly bendable, In the end the amp needed about 60cm depth on the desk (or shelf).
b) While sound quality as a headphone amp was really excellent, I found it less convincing as preamp (sound quality and noisy preamp on/off switch).

Later I owned the V281 for about 3 years. This had a better form-factor for my needs. Sound quality as a headphone amp is also excellent.
As a preamp, sound quality was about the same as the GS-X, In both cases I preferred the direct connection DAC to active speakers. In addition, the clicking noise of the V281 volume knob always disturbed me to some extend.

Now I have a Benchmark HPA4:
Sound quality of the headphone amp is on the same level as the GS-X mk2 and V281. Maybe even a bit better compared to the V281, I think it creates slightly more space around each instument and separates them better.
As a preamp the Benchmark is the best of three. The difference is significant to me. I clearly prefer the connection: DAC > HPA4 > active speakers.
The volume adjustment is excellent, very small steps, very precise (also on low levels). I find this implementation better than the volume controls of the other two amps.

Considering only the sound quality of the headphone output, these three amps are very close together. It also depends on the headphone you are using. All my comparisons are based on:
DAC: Resonessence Mirus Pro OR Crane Song Solaris. Headphones: Sennheiser HD800 and HD800S. Speakers: previously: Genelec 8040, now: 8341. I only used balanced outputs & inputs an all devices.

 

[JeffMann]

I would like to know whether the HPA4 has the power to optimally drive my HiFiMan Susvara headphone (which has a sensitivity of 83db at 60ohm)? According to the manual, the HPA4 only outputs about 2.6W into 45ohm and probably <2W into 60ohm. The new Nimbus US4+ apparently outputs about 6W into 60ohm.

Jeff.

 

[etc6849]

My HD800's are 300 ohm, but they are 102dB/1V efficient. I usually have more than 35dB of volume control left (-20dB to +15dB) on most tracks, and I listen to a lot of audiophile recordings so they aren't very loud to begin with.

If you are close to Columbia, SC we can find out together as I'd love to hear those headphones, but I think you would be fine seeing as how I have 35dB left on my volume dial.

For the price difference, and given the top level performance of the HPA4 which has lower distortion, I would try the Benchmark first. They are great to deal with and have a return policy if you don't like it for whatever reason (I bet you will though).

I would like to know whether the HPA4 has the power to optimally drive my HiFiMan Susvara headphone (which has a sensitivity of 83db at 60ohm)? According to the manual, the HPA4 only outputs about 2.6W into 45ohm and probably <2W into 60ohm. The new Nimbus US4+ apparently outputs about 6W into 60ohm.

Jeff.

 

[JeffMann]

My HD800's are 300 ohm, but they are 102dB/1V efficient. I usually have more than 35dB of volume control left (-20dB to +15dB) on most tracks, and I listen to a lot of audiophile recordings so they aren't very loud to begin with.

If you are close to Columbia, SC we can find out together as I'd love to hear those headphones, but I think you would be fine seeing as how I have 35dB left on my volume dial.

For the price difference, and given the top level performance of the HPA4 which has lower distortion, I would try the Benchmark first. They are great to deal with and have a return policy if you don't like it for whatever reason (I bet you will though).

I live in Salt Lake city so we are geographically far apart. I also own a HD800 which is easy to drive, but my Susvara is much more inefficient and it soaks up power like a sponge. I presently use a Violelectric V281 headphone amplifier which outputs 4.5W into a 60 ohm load, and I "feel" that it's barely adequate when it comes to optimally driving the Susvara - although it is easily powerful enough to drive my HD800 headphone. I have noted that a number of Susvara owners claim that their Susvara sounds much better when using speaker amps, but I am wary of going in that direction because I suspect that speaker amps lack the finesse of headphone amps like the HPA4 or the Nimbus US4+.

Jeff.

 

[biosailor]

Some years ago, I owned a Headamp GS-X mk2. I sold it, because:
a) its form-factor. It needed too much space. The cable between its power supply and the actual amp is rather huge and hardly bendable, In the end the amp needed about 60cm depth on the desk (or shelf).
b) While sound quality as a headphone amp was really excellent, I found it less convincing as preamp (sound quality and noisy preamp on/off switch).

Later I owned the V281 for about 3 years. This had a better form-factor for my needs. Sound quality as a headphone amp is also excellent.
As a preamp, sound quality was about the same as the GS-X, In both cases I preferred the direct connection DAC to active speakers. In addition, the clicking noise of the V281 volume knob always disturbed me to some extend.

Now I have a Benchmark HPA4:
Sound quality of the headphone amp is on the same level as the GS-X mk2 and V281. Maybe even a bit better compared to the V281, I think it creates slightly more space around each instument and separates them better.
As a preamp the Benchmark is the best of three. The difference is significant to me. I clearly prefer the connection: DAC > HPA4 > active speakers.
The volume adjustment is excellent, very small steps, very precise (also on low levels). I find this implementation better than the volume controls of the other two amps.

Considering only the sound quality of the headphone output, these three amps are very close together. It also depends on the headphone you are using. All my comparisons are based on:
DAC: Resonessence Mirus Pro OR Crane Song Solaris. Headphones: Sennheiser HD800 and HD800S. Speakers: previously: Genelec 8040, now: 8341. I only used balanced outputs & inputs an all devices.

I basically had the same hesitations about the GSX-Mk2 as a pre-amp: while the sound was good, no question, it was a noisy pre-amp. The amp section needed to be placed far away from the power supply, and for this the power cord was too short. When I turned up the volume control, there was a noticeable hiss that was just too high for a good pre-amp. In addition, there was a slight hum and buzz, most likely originating from the GSX-Mk2, but I could never quite prove it. This left me with the situation of having to replace the GSX-Mk2 with a different pre-amp, and the Benchmark HPA4 seemed to be just the right machine for the purpose.
But what if the pre-amp wasn't the culprit and the power amp was to be blamed for the humming noise? Eventually, I could've ended in replacing both, the pre-amp and the power amp in my audio chain!
About two weeks ago, I discovered a demo model of a Devialet 120 sitting in the shop window of one of the local HiFi dealers. Besides looking distinctly smashing, there was a flat pizza box in a shiny aluminium housing that had everything, from DAC to pre-amp to power amp. No cabling except power and loudspeaker cables required, no experimenting with pre-amp/power amp replacement. I asked the dealer if I could try the unit at my place, and half an hour later, I drove away with this shining box to test the machine for five days.
At home, all it took was to connect it to a power socket and hook up my speakers. After turning on the unit, I put my ears onto the speakers: NOTHING, dead quiet, no hiss, no noise, no nothing. Super quiet instrument. Increasing the volume knob (which is an incredibly nice remote control) ever more, the system remained dead quiet.
And the sound was just about fantastic: very fast, detailed, but never harsh sounding. Just about excellent!
It took me five minutes to decide that this is the unit I am going to keep for the next years to come, at least for my two channel system. It also frees my GSX-Mk2 for exclusive headphone listening. For this, the GSX-Mk2 is truly a truly great headphone amp! But I doubt about its usability as quality pre-amp. I was set to go for the Benchmark HPA4 as my new pre-amp section, but the prospect of solving all my problems with one single digital equipment, was too tempting!
Here's a picture of a flashy 'pizza box' replacing a complicated and clunky setup!

 

[M Siau]

I would like to know whether the HPA4 has the power to optimally drive my HiFiMan Susvara headphone (which has a sensitivity of 83db at 60ohm)? According to the manual, the HPA4 only outputs about 2.6W into 45ohm and probably <2W into 60ohm. The new Nimbus US4+ apparently outputs about 6W into 60ohm.

Jeff.

We had the HiFiMan Susvara headphones at AXPONA and the HPA4 drove them beautifully! We will be in your backyard at RMAF in October, we will have the HPA4 and a selection of headphones to try out. One of my favorite parts of CanJam is all the major headphones are there and for the most part you can borrow headphones for a quick listening test on different amps.
Hope to see you at RMAF!
October 5-7

 

[JeffMann]

We had the HiFiMan Susvara headphones at AXPONA and the HPA4 drove them beautifully! We will be in your backyard at RMAF in October, we will have the HPA4 and a selection of headphones to try out. One of my favorite parts of CanJam is all the major headphones are there and for the most part you can borrow headphones for a quick listening test on different amps.
Hope to see you at RMAF!
October 5-7

Why should the Benchmark HPA4 be able to optimally drive a Susvara headphone when it only outputs ~2W into 60 ohm, when my Vioelectric V280 headphone amplifier (which outputs >3W into 60ohm) cannot cope at all, and where I have to use my Violectric V281 headphone amplifier (which is more powerful) to drive my Susvara headphone? Is there some other "factor" at play?

Jeff.

 

[negura]

It's well known Vioeletric doesn't cope with HE-6, which are similarly inefficient.

However, to achieve 90dB SPL you only need: 19.69 mW. Max available power doesn't really tell if an amp is capable to drive these headphones. There is a lot more to it, including PSU design.

Source:
https://www.innerfidelity.com/images/HiFiMANHE6.pdf

 

[astrostar59]

It's well known Vioeletric doesn't cope with HE-6, which are similarly inefficient.

However, to achieve 90dB SPL you only need: 19.69 mW. Max available power doesn't really tell if an amp is capable to drive these headphones. There is a lot more to it, including PSU design.

Source:
https://www.innerfidelity.com/images/HiFiMANHE6.pdf

The V281 drives the difficult HE-6 with pants-flapping aplomb, making this a highlight of my listening for the week.
Read more at https://www.innerfidelity.com/conte...eadphone-amplifier-page-2#lBgo2gzZVXSU7eJ3.99

 

[negura]

I heard it with my HE-6. It's not even in the ballpark of driving them well, all imo. We also tried all the settings. And it's not because it doesn't have enough power, as there was more than enough volume range. Something amiss with that design. Other more efficient headphones fared better.

Also that article is old. Since 2015 hobbyists had a lot more experience with getting what's needed for inefficient headphones, and so did some amp builders.