Benchmark HPA4

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by skem, Aug 8, 2018.

  1. skem

    skem Friend

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    [​IMG]

    Benchmark has released a new headphone amplifier that doubles as a stereo pre-amp. The concept behind the volume-control portion is not dissimilar to a stepped attenuator, just done with relays:

    "Features features relay gain control... The gain control has 256 steps in 0.5 dB increments. Relay closures are precisely timed to deliver silky-smooth volume changes. ... Includes 4 independent 256-step attenuators: two for the L&R headphone outputs, and two for the L&R line outputs. [for] total of 64 precision relays."

    Which means that eventually this thing is going to crap out when the relays fail, but that should be a good long while, and in the meantime it should have better channel matching than most pots and more uniform impedance presentation to the source.

    But all that fancy business surrounds the volume control. What really matters to me is that everything is going through active amplification circuitry. What does the amplifier sound like is the key question.

    It cost $3000, so it had better sound fantastic.

    Before I give my views, I'll note that some SBAF members have heard this at shows at like it.

    @neogeosnk heard this at CanJam SoCal and writes:
    • best amp at canjam. Very transparent yet meaty. Just ordered mine.
    @m17xr2b heard this at Canjam London and writes:
    • With the HD650 I was really surprised how good the HPA4 is, sounded very similar to my daily amp the Peak/Volcano with my reference tube but not as extended in the bass. Great detail and glorious midrange, I wouldn't have said it's solid state since natural and clean is rarely found there.
    • The HPA4 does a beautiful job on the HD800S, high end is tamed nicely, similar detail to my modded HD800, low end had lean but very well controlled impact, typical well driven HD800.
    • Meze Empyrean...with Benchmark HPA4 and dac3 hgc, unfamiliar but quality recordings these sounded great, bass stands out a controlled extended and good weight
    @SPAZ told me via email:
    • I've been going back and forth between the mjolnir2 and hpa4. The differences are not that discernible. As of right now I have only done testing with Utopia, which isn't power hungry.
    OK - those sound positive. So, I purchased this thing and demo'ed it. I also gave it to @porkfriedpork, who took it home to demo on his own system. Here are some impressions.

    Physical

    It has a nice footprint—compact and fits on top of the DAC3 if you have one. But it's kind of an ugly thing. The bright TFT display is totally charmless. It's boxy and sort of lame. It's compatible with the Benchmark remotes, which I happen to really like—although their LED is not that powerful so not great if you're trying to use the remote at great distance. Not a big deal, but it has a thing where it mutes the output of headphone jacks when they are unplugged, so when you reconnect a new pair, it takes a second or so for the sound to come on. This makes the amp hard to use for A/B testing.

    Sound

    With HEK:
    I did side-by-side comparisons with Benchmark HPA-2 (the amp that is built into the Benchmark DAC3 HGC), with Leptoni DT-Alpha (a $4K tube amplifier), with my refurbished Pioneer M22, and my Pass Labs XA30.8. These were all done using Benchmark DAC3 as the source.

    HPA4 versus Benchmark HPA2: Both of these amplifiers are quite competent solid state devices. HPA4 is a noticeable upgrade. It has a very slightly thicker sound with less of the HPA2's edgy quality. The edgy quality of the HPA2 is really annoying, and is why I initially transitioned to tube amps—it was driving me up the wall. If I had the HPA4, I might not have made that transition. The HPA4 also had more detail. Not gobs more, but a touch more. That's an achievement, because third-order distortion often creates the impression of detail, but at the cost of fatiguing edginess—this indicated to me that HPA4 really was a better (lower distortion) amplifier than HPA2—it wasn't just aural trickery. That advantage comes with a cost, however: the presentation seems more distant.

    Verdict: HPA4 > HPA2, but .... is it worth the extra $3,000? In my opinion, no.

    HPA4 versus Leptoni DT-Alpha: These are not really comparable amps, one is solid-state, the other tube. The Leptoni (or the loaner, which has a very carefully selected group of tubes) is a very colored amp with loads of warmth. I found it was able to drive my HEK very well. It has nice bass and good high-end. However, it did have an unclean quality to the bass. Leptoni's sound signature (or at least that of the tubes with the Loaner) causes the chest voice of male vocals to disappear behind their headvoice—which is consistent of other reports of carved-out mids. By contrast, HPA4's response is totally flat. Needless to say, HPA4 is also more detailed than Leptoni. So, HPA4 is a technically more capable amp than Leptoni. But, which would I choose given the chance to have one for free? I totally take the Leptoni. Much more fun.

    Verdict: Draw. Technically HPA4 is better, but I prefer the Leptoni.

    HPA4 versus Pioneer M22 & Pass Labs XA30.8: No contest. HPA4 loses to both on all fronts when tested with HEK.
    With HE-6: HPA4 cannot power HE-6. It sounds like the HE-6 was killing the thing. It produced a terrible, withered sound. It was so incredibly bad that I just unplugged it and put it back in the box after 10 seconds. Benchmark suggested I remove 10dB attenuators and try again, but I wasn't interested. Getting terrible to sound acceptable is not my idea of a $3000 amplifier. FWIW, this test was done using Soekris 1541.

    As a pre-amp: @porkfriedpork reports that the HPA4 just killed the stage. This seems to be something shared by all Benchmark products—because their DACs, while excellent in every other respect, also seem to have no stage.

    Final Verdict
    This is a competent solid-stage headphone amplifier. Super clean, low distortion, flat FR. Despite its size, it is not all that powerful, and that limitation makes itself evident with power-hungry planars. It is not worth $3000 in my opinion. There are other totally-dry options out there for less. Really a fail at this price point for me. Bear in mind that several others seem to like this head-amp, even though I did not. This may come down to a planar vs. dynamics thing, but the stage-killing pre-amp performance makes me think there are other limitations lurking under the hood.
     
    Last edited: Aug 8, 2018
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  2. neogeosnk

    neogeosnk Friend

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    Still stand by my comment, is the best sounding SS amp I've ever heard. It's 10x more than a jot but for me this is end game. I've had zero problems driving all planars that I own and would probably blow them out if I went past 3/4. Dynamics.. forget about it, drives everything with ease. Pre-amp is pretty transparent for me with no coloration or loss in sound stage. This amp needs a minimum of 80 hours burn-in to open up the sound stage and dial in the bass.
     
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  3. skem

    skem Friend

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    FWIW, I did not give the amp 80hrs. More like 0.8 hrs.
     
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  4. SPAZ

    SPAZ Rando

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    I did not notice any lack of soundstage with this amp. Very happy with it so far.
     
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  5. Armaegis

    Armaegis Friend

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    I do find myself wondering if this thing is even worth keeping on the radar since I have an AHB2 and have had no noise issues with my headphones (granted I do not have any sensitive iems wired for balanced use).
     
  6. skem

    skem Friend

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    If you hav a volume control, I wonder if it offers any advantages.
     
  7. k4rstar

    k4rstar Britney fan club president

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    Any chance of a loaner of one of these? If the unit in question has the prophesied 80 hours of semi-conductor burn-in time of course. I would be very keen to try it.
     
  8. Armaegis

    Armaegis Friend

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    I always seem to buy your stuff. I swear if you get this and then later change your mind for something else, I'm in trouble...
     
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  9. skem

    skem Friend

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    I just pulled apart HPA2 (not HPA4, but I suspect they’re similar).

    HPA2 is a directly-coupled, low-distortion L49860 op-amp under what looks to me like bog-standard implementation. That would explain the precise but relatively dead sound of the amp. Probably has huge amounts of feedback. This is consistent with notes here and Marv’s verdict here.

    I’d be surprised if HPA4 were any different inside. Maybe one of the current owners can open it and look.
     
  10. purr1n

    purr1n Finding his inner redneck

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    HPA4 is based on THX AAA no? From what I've experienced, the Massdrop THX AAA, it's already pretty damn good, and that's with the switcher! I haven't had time to power with it with a real LPS. I'd imagine the Massdrop version to not merely be competitive / a small notch better than Jot, but a jump from it.
     
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  11. SPAZ

    SPAZ Rando

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    On their website I don't see any proof the HPA2 has anything based off THX technology.
     
  12. purr1n

    purr1n Finding his inner redneck

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    We should ask Benchmark if we could get a loaner.
     
  13. Elnrik

    Elnrik Super Friendly

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    Tell them we won't butcher the measurements like Amir did, and they'll probably give you anything you want.
     
  14. skem

    skem Friend

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    They have a 30-day trial program. You would be welcome to use that for measurements and individual impressions. Obviously, not a loaner unit for (wide) circulation. Of course, the idea is one should have intent to buy if it’s good enough.
     
    Last edited: Aug 11, 2018

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