Review and Measurements of Benchmark HPA4 Headphone Amp/Pre

[Schackmannen]

Jaw dropping performance figures! Can we get an XLR/balanced output power measurement at 300 ohms? Also do you plan to do any listening tests with it?

It should be the same performance as the 1/4 inch measurement.

 

[JJB70]

What is sad, really, are companies asking so much more for likely so much less. In any case, in the scheme of things, this is much cheaper than, say, the Sennheiser HE-1... but you don't get fancy marble and a lot of tubes.

That Sennheiser is jewelry and audio theatre, its target market is rich people wanting a statement and I suspect it was well received by Russian oligarchs, middle eastern oil sheikhs, silicone valley billionaires, Chinese super wealthy etc. Benchmark seem fundamentally different from that sort of product. Their products avoid unnecessary glitz and bling, the price point seems to be a result of the cost of product development and manufacture rather than a random point selected to be reassuringly expensive for those who think most exensivest is bestest and it is about real engineering substance. For all that it is also true that the vast majority of Sennheiser production is of much more prosaic equipment that does offer real value for money. For example there is a very good reason why the HD600/650/660 have been a default recommendation for so many years and they make some very good and very affordable IEMs. So I don't begrudge them going over the top with the occasional statement to rake in money from the super rich.

 

[amirm]

Jaw dropping performance figures! Can we get an XLR/balanced output power measurement at 300 ohms? Also do you plan to do any listening tests with it?

I did listen. It is in the review. 300 Ohm results are also there as there is no electrical difference between XLR and 1/4 inch on the HPA4. XLR connection simply separates the shared negative wire for the two channels. Otherwise it is the same as 1/4 (i.e. no increased power).

 

[Anders V]

I don’t recall what input signal level you use when measuring devices like these, but if you use normal consumer device level, I note that the Benchmark DAC3 and the HPA4 can agree to use professional levels (12 or 15 dB higher if I recall their documentation). So that combination should yield even higher SINAD numbers.

Btw, I bought a THX AAA 789 after a friend recommended it and referenced your review. It’s wonderful, my only problem with it is the low price... So I bought the Benchmark duo, for another location. They are both great, but the 789 could not drive the famously challenging Hifiman Susvara, which the Benchmark handles well.

 

[amirm]

I don’t recall what input signal level you use when measuring devices like these, but if you use normal consumer device level, I note that the Benchmark DAC3 and the HPA4 can agree to use professional levels (12 or 15 dB higher if I recall their documentation). So that combination should yield even higher SINAD numbers.

I played extensively with that. Differences were actually small. At the end, I did settle on using sweeps to a bit over 11 volts. I used the same with the THX amp by the way which allowed a fair comparison.

 

[boXem]

Impressive performance!
@amirm I am not sure to understand your comment on the relation between the noise and the "non analog attenuator". A stepped attenuator is analog .

 

[garbulky]

I did listen. It is in the review. 300 Ohm results are also there as there is no electrical difference between XLR and 1/4 inch on the HPA4. XLR connection simply separates the shared negative wire for the two channels. Otherwise it is the same as 1/4 (i.e. no increased power).

Doah you did listen (and I clearly didn't read properly!) I take it this is not a fully balanced amp right?

 

[amirm]

Doah you did listen (and I clearly didn't read properly!) I take it this is not a fully balanced amp right?

It is where it matters which is the input side.

 

[phoenixdogfan]

Yes. Some gear is more attractive than others. Accuphase, Lux, McIntosh. But I've got some of this Benchmark stuff, and can report that once you turn the lights off, they all look the same. And after a few beers, it starts to look better.

That's what everybody who ever tried to fix me up with a blind date said.

 

[amirm]

Also an FFT of the 19+20 kHz IMD test like you did in the AHB2 test would also be greatly appreciated.

Here is that measurement:

As you see, the IMD shown (blue) is the same as the analyzer testing itself (red). IMD tones are generated using a DAC in AP hardware so they are not as free of distortion as the analog generator are for single sine wave.

Going with it anyway, the worst case spurious response is about 120 dB below the fundamental tones. So superb.

This is for pre-amp output by the way.

 

[amirm]

And here is the headphone out:

It has just a hair more distortion at 4 volt output.

 

[amirm]

Could you please do an internal loopback test of the AP at 5.7 volts and one loopback test where you use the same wires as you do for testing the amp?

This is with cable:

Going internal loopback shaved a hair from this but not beyond the run to run variation.

SINAD matches the Benchmark HPA4 (due to noise dominating) but note the absence of any distortion products visible in FFT.

 

[JohnYang1997]

This is with cable:

View attachment 29811

Going internal loopback shaved a hair from this but not beyond the run to run variation.

SINAD matches the Benchmark HPA4 (due to noise dominating) but note the absence of any distortion products visible in FFT.

Hi Amir, may i have some spectrum graphs with load? Like 120mwmw 500W 1W 32ohm or something like that. (of hpa4 of course)

 

[maxxevv]

Pity Benchmark doesn’t offer the 3-year warranty outside the US... Moon-Simaudio does (10-year!). Bryston does (20 year!!).

The 10 / 20 / lifetime warranties are often a fallacy. If you read the fine print, you'll get spares / repairs / direct replacements if the model you bought is still in production. AND its not a result of "wear and tear ".

I sure can think of a few things such as relays and capacitors subject to wear and tear failure though.

 

[ShiZo]

Awesome review Amir!!!! So there is literally no difference between xlr and 1/4 headphone out? Not even slightly? If so that's pretty awesome.

 

[BYRTT]

Awesome review Amir!!!! So there is literally no difference between xlr and 1/4 headphone out? Not even slightly? If so that's pretty awesome.

Know example is another design but for Neurochrome HP-1 by @tomchr, he told below about difference for 1/4 jack verse 5 pin XLR, note his HP-1 is also not a ballanced output but single ended:

QUOTE That little bit of shared ground impedance in the 1/4" phone jack actually degrades the channel separation from 115 dB to 90ish dB. That's physics for you. There's no magic voodoo here. It's all Ohm's Law UNQUOTE

 

[anmpr1]

As others have said, Benchmark and their partners at THX have reached (or are reaching) the point where their gear cannot be measured apart from the 'noise' inherent in the measuring device. I never paid much attention to THX before Benchmark, because I always associated them with movies, and Jurassic Park/Star Wars special effects isn't my thing. I believe THX began with designer Tom Holman. I remember Tom from the phono stage of the Advent 300 receiver. And his APT preamp. Both well thought of, cost efficient designs, for their time. No one back then could have predicted these Benchmark products. Can you imagine being able to take their AHB and HPA gear back to 1980 for Audio or Stereo Review test them? What their reaction would be?

 

[JohnYang1997]

Awesome review Amir!!!! So there is literally no difference between xlr and 1/4 headphone out? Not even slightly? If so that's pretty awesome.

As the logic goes. It's not traditional balanced output. Just separated ground point. Same as the one in Neurochrome Hp-1.
In the specification, there is only one headphone out spec. And in the manual "
The right-hand jack is
a 4-pin XLR headphone jack that features dedicated returns for each channel.

The main purpose of the second connector is
to provide a high-performance alternative to
the traditional TRS phone jack."

It's impossible to have perfectly same balanced out and single end out if the using the same circuit. The noise has to be doubled, output impedance has to double, output voltage swing(power for high impedance)will be doubled(quadrupled).

 

[Schackmannen]

@amirm Thank you for running all these tests! Very impressive that the analyser and not the amp becomes the limiting factor in some of these tests. Also I find it interesting that the harmonic distortion in the loopback test seems to have decreased when using an external cable, or is it because of the slightly higher level (5.7 vs 5 volts) that the ratio of distortion is lower compared to the internal loopback test?

 

[Ralf Stocker]

A battle between AP and Benchmark!