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Benchmark HPA4 Headphone / Line Amplifier Impressions

Discussion in 'High-end Audio Forum' started by negura, Apr 8, 2018.
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  1. negura
    Announced recently in the HF vid, the specs & pre-oder page is live.


    Spec highlights:

    • THD < -125 dB (0.00006%)
    • SNR > 131 dB, unweighted, 20-20 kHz
    • SNR > 135 dB, A-weighted
    • Crosstalk < -133 dB @ 1 kHz, -116 dB @ 10 kHz
    • 256-Step Fully-Balanced Relay Gain Control, 0.5 dB Steps

    Yes, it is not cheap, but this imo will very likely have end-game performance.
    Last edited: Apr 8, 2018
  2. etc6849
    The engineering of the volume control looks incredible as discussed in their recent application note:

    I have some Bencmark AHB2 amps in my theater as well as their DAC3 I use with my Focal Utopia's and Sennheiser HD800's, and I am still impressed every time I listen to either system. If the HPA4 is anything like the AHB2 amps I am now accustomed to, I feel like I must pre-order the HPA4 although $3k is a lot of money to me and my wife may not like it as I promised I would quit spending money on gear (and haven't felt the need in my theater after the AHB2s I added in 2017).

    For the AHB2 amps (same THX AAA topology used in Benchmark's HPA4 headphone/preamp):
    The background sounds in music that were presumably lost to inter-modulation distortion and even my previous amp's much much higher noise floor, are so crisp and clear that things sound absolutely real.

    An amp such as the AHB2 has 100's of times lower distortion at low volume levels compared to even the best consumer amps available at any price. I too was skeptical until I heard and owned some, but this lower noise floor, lower THD and IMD of the THX AAA design is very audible once you experience it. Sounds come out of black space with no hiss being heard unless it is in the recording itself. As an example, vocals seem to endlessly decay, and you can honestly hear the room the recording took place.

    While a lot of thought and time went into my system such as actively tri-amping 5 channels with FIR filters, room treatments, crossing to multiple subs that are individually time aligned and fed a mono signal, the Benchmark AHB2's were the missing piece I'd been looking for a very long time. Well recorded HD tracks like those from AIX Records are so real now that one is literally transported in time and space.

    Theater front new.jpg
    Last edited: Apr 12, 2018
    lantian, bidn, gibsonsg87 and 8 others like this.
  3. Liu Junyuan
    Very interested.
  4. Tobes
    I also utilize the AHB2 power amp to drive my speakers and will be following the HPA4 with great interest.
    I've hardly used my DIY F6 since getting the AHB2 and can't imagine being without it.
    The HPA4 has all the features I require and would allow me to do away with both my Bryston BP26 preamp and BHA-1 HP amp.
    Pretty excited about the potential of this device.
    Last edited: May 15, 2018
    etc6849 likes this.
  5. Whitigir
    The specifications seem to be better than GSX MKII ?
    alphanumerix1 likes this.
  6. negura
    It should be. The AHB2 using similar technology is one of the few amps with better real specs as measured by many 3rd parties, than GSX.
  7. etc6849
    I called Benchmark today to follow up on my preorder. They told me that the remote for the DAC3 will work fine with the HPA4, and that it looks like around June 7th is when mine will ship out. I can't wait :)

    If anyone knows of any formal reviews with measurements, please post them here. I am really curious how much of a difference it will make over the excellent Benchmark DAC3's HPA2 headphone amp.

    I think we should see 20-35dB more of dynamic range from the headphone amp (HPA4 versus HPA2), but the limiting factor in the signal chain is the DAC's output so perhaps we will see a little less than 20dB improvement. What is more interesting is 16 bit audio has a dynamic range of 96dB with no dithering or closer to 120dB of perceived range with dithering... This means to me there is no where else to go after owning the HPA4.
  8. Tobes
    Hmm.....no other reports regarding this amp, thought there might be some more impressions from recent shows?

    I'm considering pre-ordering and also contacted Benchmark about the remote.
    Since I'd be using the preamp functionality for my main system the HPA4 would reside in my main rack and distant from my HP listening seat. So I checked to make sure the remote would allow switching between the Line and HP attenuators (obviously the touch screen allows this functionality). Benchmark confirmed it does and also that the remote is the same as the DAC3 remote - as mentioned above by @etc6849.

    This is fine but it appears there will be no buttons to direct select the analog inputs of the HPA4(?).
    Benchmark also confirmed that the remote would not allow adjustment of L-R balance - which is disappointing because when required I'd like to be able to do this from my listening seat.
  9. etc6849
    I am sure the HPA4 will not disappoint us. I also have the Utopia's I bought last black Friday, and I bet I am in for a treat as I like to hear every last detail as distortion free as possible.

    Hopefully they post the manual soon for us to study the measurements while we wait. The anticipation on this thing is killing me.
  10. biosailor
    Any news when Benchmark's HPA4 is expected to be shipped to customers?
  11. Tobes
    From above, it looks like pre-orders to US/Canada may ship from the 2nd week of June?
    I'm in Australia and emailed Benchmark regarding shipping dates - they advised:
    "once we begin shipping 3rd week of June, we will be shipping worldwide"
    I've ordered mine through a local dealer and look forward to putting it through its paces.
  12. biosailor
    OK, so third week of June then. I am VERY curious to hear what people say about the pre-amp section. I am primarily interested in replacing my current pre-amp with the HPA4 to feed my power amp.

  13. Tobes
    That's what I'll be doing and I will compare it to the Bryston Bp26 - which is a neutral, low distortion and dynamic sounding preamp - driving the Benchmark AHB2.
  14. biosailor
    Super, very interesting! How's the Benchmark AHB2. This is another amp I keep following.
  15. Tobes
    Love the Benchmark AHB2, it's a neutral window to the music - it just sounds right to me. It's also compact, cool running and sounds great from switch on - which makes it extremely practical.
    The competence of the AHB2 has given me the confidence to buy the HPA4 and I've also ordered a DAC3 L to complete the chain.
    To be honest I'm sceptical whether the HPA4 will show significant improvement over the BP26, which itself has distortion levels an order of magnitude below typical hifi gear. The HPA4 boasts significantly higher S/N ratio, though whether this will translate to any practical advantage remains to be heard. At least I'll reduce my box count.
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