[JeffMann]

JeffMann, Benchmark has a 30 day return policy. It's probably worth it to give it a shot to see if it works out for you or not.

I am giving that recommendation a great deal of serious consideration.

Jeff.

 

[Tobes]

If you want what sounds real, e.g. something like a good binaural recording will transport you and provide an incredible out of the head experience, your goal should honestly be to remove as much distortion as possible

Sounds amazing with the Utopia headphones. I know John Siau already stated there is no measurable break-in with the HPA4 - but it seems to sound better the more you listen.

The HPA4 will sure let you know what your transducers can do.
Up until a week ago I was using the HPA4/AHB2 with Harbeth m30.1 monitors - pretty nice speakers. But the Harbeths just couldn't match my Focal Utopia headphones via the HPA4 for apparent speed and clarity causing a bit of a disconnect between headphone and speaker listening.
I took my AHB2 to a store and listened to the ATC SCM19 monitors and was blown away by the transient clarity and dynamics of the ATC's. When I got them home with the HPA4/AHB2 the ATC's sounded simply superb. I highly recommend this speaker to anyone with the Benchmark amps.
Perhaps it's no coincidence that ATC are also a studio orientated brand with an emphasis on neutrality, low distortion and high dynamic range. I wonder what adding a second AHB2 and running in mono mode would add to the mix? ATC recommends amps from 75-300Wpc?

 

[flyte3333]

Hi @jsiau

I have MrSpeakers planar headphones that have a ruler flat 13 ohms impedance.

What is the power (and separately the current) output of the HPA4 at 13 ohms, for both 6.3mm and XLR4 headphone outputs?

Many thanks

 

[Christer]

Jeff,

The HPA4 is a scaled down version of the Benchmark AHB2 power amplifier. Both of these amplifiers feature the patented THX AAA(TM) technology that includes feed-forward error correction. This system keeps the amplifier distortion free when heavily loaded with low impedances and/or high output levels. It also prevents the zero-crossing transients that are normally produced by conventional class-AB amplifiers. These zero-crossing transients are normally produced by the crossover transition between the complimentary (push-pull) output devices. Conventional amplifiers use biasing to mitigate some of the crossover distortion, and attempt to remove more of this using feedback. In contrast, the AHB2 and HPA4 take an entirely different approach. The outputs of the Benchmark amplifiers are driven through the crossover region using a supplementary feed-forward amplifier. This supplementary amplifier prevents push-pull crossover transients allowing distortion-free output at low levels (unrivaled first-watt performance) even when driving very low impedances.

The AHB2 is distortion free into all rated loads. By "distortion free" I mean that it can be shown that the distortion will never reach the threshold of hearing (0 dB SPL) when driving loudspeakers. If we do the math, we can see that the same is true when driving headphones. Furthermore, the 132 dB SNR of the AHB2 allows it to be used at levels well below the rated power without encountering audible noise. In contrast, most power amplifiers will produce audible noise in a set of headphones (unless the headphones are unusually inefficient). So, the AHB2 will make an excellent headphone amplifier and it can be used with any headphone without producing audible noise or distortion. The risk is that the AHB2 has enough output voltage and power to instantly fry most headphones (not to mention your ears). If an AHB2 is used with headphones, the output of the upstream DAC must be attenuated so that the noise produced by the DAC will not be the limiting factor. An HPA4 line stage can be used for this purpose.

The AHB2 and HPA4 will sound virtually identical when driving headphones (if the gain staging between the DAC and AHB2 is optimized for headphone use). With either amplifier, there will be no audible noise or distortion, and you get a frequency response that extends from 0.1 Hz to over 200 kHz. The extended frequency response keeps the entire audio band phase accurate. This phase accuracy contributes to a precise 3-dimensional stereo image. Both amplifiers will sound the same but the HPA4 is safer and more convenient when using headphones.

The Susvara HE6 reaches 83.5 dB at 1mW assuming an impedance of 50 Ohms. At 50 Ohms, 1 mW is 0.224 Vrms. The HPA4 will cleanly deliver 10.8 Vrms into 45 Ohms (see page 50 of the HPA4 manual). 10.8 Vrms is 33.7 dB above 0.224 Vrms. This means that the HPA4 can drive the HE6 to an output level of (83.5 + 33.7) = 117.2 dB SPL. This will be uncomfortably loud.

The AHB2 can easily produce 28.3 Vrms on each channel when driving the HE6. 28.3 Vrms is 42 dB above 0.224 Vrms. This means that a single AHB2 can drive the HE6 to an ear-splitting output SPL 125.5 dB SPL (if the headphones don't let out smoke first). Add 6 dB if you are using a pair of AHB2 amplifiers.

Hello John, I would be interested to hear from you how much of an audible, not measurement difference, I could expect to hear between HPA4 and my HPA2 in my DAC 2?
I am currently using the headphone section of my DAC2 in combination with a Chord Qutest DAC instead of the slightly less resolving and less transparent DAC in my DAC 2.
With headphones like the HEKV2 I can hear a clear improvement in transparency and resolution with hi res master files of large scale classical music where I know how things actually sounded in the hall,between the inbuilt dac of DAC 2 and the Qutest. The Qutest is clearly better.
But the headphone amp of DAC2 sounds very good I have to say clearly revealing the difference between the two dacs.
Cheers Christer

 

[Tonybo]

Hi everyone (first post)! I have just taken delivery of my HPA 4. Sounding very nice connected to an AHB2 and being fed by my DAC2 HGC (on XLR1). I didn’t know the DAC2 could sound so good! Infact I had been planning on moving the DAC2 on to recover some funds, and using a RPi HAT DAC instead, into the HPA4. May have to re-compare those options.

There is a problem however. When I connect the RPi DAC to the RCA inputs of the HPA4 the music is pretty much drowned out in mains hum. Turns out the RCA inputs on the HPA4 have a lifted earth, which is not the case for the equivalent inputs on the DAC2 HGC, with which in (pre-amp mode) the RPi DAC works perfectly. I also have a phono stage that I want to connect to the other RCAs, also a wall wart powered device with no proper earth, which also works poorly in this scenario.

So have I got a faulty unit? Maybe there is a setting for this? Any thoughts would be much appreciated!

Finally, what confidence can we have in the longevity of the screen, given that it is a critical interface?

 

[SalR406]

Finally, what confidence can we have in the longevity of the screen, given that it is a critical interface?

I had this same thought. What will that screen be like in 10 years... 20 years? A head amp is not a component that goes obsolete quickly. Should be a keeper for a long long time. Maybe an unfounded concern. Who knows...

 

[Christer]

I had this same thought. What will that screen be like in 10 years... 20 years? A head amp is not a component that goes obsolete quickly. Should be a keeper for a long long time. Maybe an unfounded concern. Who knows...

With my DAC 2 I use the remote for 99,9% of the time. I can see the need for touchscreens on portable stuff .But absolutely NO NEED whatsoever on a stationary device like the HPA4.
Strange design choice imho.

 

[Tonybo]

The thing is, it is very configurable. I have set mine to dim then switch off after a couple of minutes, it only lights up if you then adjust something again, so the usage is nicely minimised.

how much of an audible, not measurement difference, I could expect to hear between HPA4 and my HPA2 in my DAC 2?

In an attempt to answer I have tried to compare the HPA2 and HPA4 using a file playing on the DAC2 using Grado SR325 (perhaps not the quality of the HEK). I initially felt that the HPA2 sounded better, to my shock. I then went off to assemble and fit a better set of balanced interconnects and tried again. Did this do it, I don't know for sure but at the second sitting i find them very close and suspect level matching was the factor. Conclusion, they are very close - with the Grados.

Still looking for an opinion on the non-earthed RCA inputs of the HPA4..

 

[Christer]

The thing is, it is very configurable. I have set mine to dim then switch off after a couple of minutes, it only lights up if you then adjust something again, so the usage is nicely minimised.



In an attempt to answer I have tried to compare the HPA2 and HPA4 using a file playing on the DAC2 using Grado SR325 (perhaps not the quality of the HEK). I initially felt that the HPA2 sounded better, to my shock. I then went off to assemble and fit a better set of balanced interconnects and tried again. Did this do it, I don't know for sure but at the second sitting i find them very close and suspect level matching was the factor. Conclusion, they are very close - with the Grados.

Still looking for all opinion on the non-earthed RCA inputs of the HPA4..

Hi and thanks for your input.
No offence intended but if you want to hear the often very subtle differences between two such pro quality amps you need much better headphones than the SR 325 imho.
Although I too suspect the two amps to be very close in SQ, I very much suspect your Grado's really are a very limiting factor.

I still have a pair of those tucked away somewhere which I haven't used for many years. I bought them in the USA for use with my then portable Sony Discman in the late 90s.

When I bought them I already had a MUCH MUCH better headphone at home an electrostatic.
But they were at least an improvement on my earlier travel headphones Koss Porta Pro
For my travels and at home too by the way I have since those early days of "decent but not really good portable audio", gone through Grado's best headphones and, Sennheiser HD 650, and HD800 and now mainly use my HEKV2 both on travels and at home, with the HD800 as a backup.
Cheers Christer

 

[Tonybo]

No problem, I'm sure you're right. Need something more expensive, unfortunately however I am grounded for a while now..

 

[etc6849]

Benchmark needed some sort of way to easily show what volume level was. I remember looking it up and believe it was one of these:
https://www.4dsystems.com.au/group/4D_Intelligent_Display_Modules/

It seems like Benchmark paid a lot for the display modules they chose where most manufacturers would have used something cheaper (like just a screen only with no touch capability, a screen with a lessor processor, etc...). If these types of human machine interface displays work fine 24/7 in industrial environments, I see no reason why we would have any issues decades from now. I bet there are some very expensive industrial systems using these touch screens.

I had this same thought. What will that screen be like in 10 years... 20 years? A head amp is not a component that goes obsolete quickly. Should be a keeper for a long long time. Maybe an unfounded concern. Who knows...

With my DAC 2 I use the remote for 99,9% of the time. I can see the need for touchscreens on portable stuff .But absolutely NO NEED whatsoever on a stationary device like the HPA4.
Strange design choice imho.

 

[SalR406]

If these types of human machine interface displays work fine 24/7 in industrial environments, I see no reason why we would have any issues decades from now. I bet there are some very expensive industrial systems using these touch screens.

Ah, that's a good point. I hope you're right!

 

[etc6849]

If you do have issues with it in a decade, I'm sure Benchmark will service it for you. Definitely not the case with many audio brands though, especially some of the overseas brands.

Ah, that's a good point. I hope you're right!

 

[YooperAudio]

I'm about a month into using my Benchmark HPA4 with Senn 800S phones, balanced cable. I have a pair of AHB2 monos downstream from it. During the eval period, I tried multiple times to convince myself that I didn't need the HPA4, going back and forth with a lot of comparison listening tests with the HPA2 HP amp in the DAC3.

Every time, the HPA4 was for me a hands-down winner. I couldn't talk myself out of it, and I kind of wanted to just to save the money.

And now that I am familiar with the user interface, I like it OK. I'm probably going to suggest that for a future firmware/software upgrade, they offer the option of displaying the dB level in a BIG font on the display, just as a way to gain some insight into what the dB level setting is from 8+ feet away. But it's not that big of a deal. I'd also like to be able to set an option that would turn off the "enable both the headphone AND line out outputs concurrently" feature, and along with it, have it automatically mute the disabled output when the other one is selected. It would just alleviate a slight bit of hassle when I go to switch from line out to headphone, and I need to also fiddle with making sure both of them aren't enabled, and muting the correct channel. That would make output switching a one-butting effort by pressing the volume knob.

 

[Tonybo]

That’s a good suggestion.

Now, would you, or somebody else, be able to just check whether the neutrals on your rca inputs are floating or if they are earthed (to the mains earth pin, or to the rca outputs for example)? (Mine are not and it seems to cause problems). Would be much appreciated!