Review and Measurements of Benchmark HPA4 Headphone Amp/Pre

[SoundGuy]

Just bought the LA4. What a remarkable improvement this fantastic preamp makes! Clarity and low volume details such as ambiance, vocal articulation, imaging and reverberation tails took sound to whole new level. I am shocked.

I conclude that this incredible preamp will improve any system where your listening levels are a typically down 30 to 40 dB (which is likely the majority of systems). Simply follow Benchmark instructions - use XLR outputs into the LA4 and ensure your devices feeding the LA4 are run at their full rated output - and be prepared for a shock.

Although the LA4 is totally transparent it is still able to make a huge difference to the finer low level details within the recordings. I was unaware how low level detail is buried by typical lower quality volume controls. The LA4 proved that measurement specifications at rated output are quite meaningless when comparing devices - what matters is how a preamp behaves at -30 dB and how well it interfaces with upstream and downstream devices.

Conclusion: The ubiquitous cheap digital volume control is a terrible scam perpetrated by manufacturers - high quality active analog volume control is a must if you value great sound at all listening levels. Attenuation using digital volume control is robbing the listener of sonic detail.

 

[Sean_S]

Great question! Great observation!

The answer is that the +/- supplies track the audio.

This tracking also eliminates common-mode distortion components that would normally be produced by the OPA564. The reason for this is that audio signal is always centered between the two voltage rails in that stage of the amplifier. The common mode voltage is always nearly 0.

@JohnYang1997 Did this provide you with insight? I never saw an acknowledgement.

 

[richsto]

@JohnYang1997 Did this provide you with insight? I never saw an acknowledgement

Before I bought the LA4, I looked at it online, saw the remote had input buttons and assumed that these did something with the LA4.
After adding a DAC3L, I now realize they can select inputs but still cannot select between XLR-1 and XLR-2 with discrete codes.

The best that can be done is to disable the LA4 other inputs with only the XLR-1 and XLR-2, select a disabled input that gets you to XLR-1 and add a second commend for the next. The two-code solution is not reliable and sometime family members miss one and the mains don't work because XLR-1 is selected, and XLR-2 must be selected for HT.
My wife, says, "Why can't I just have a system that works". I have no good answer for this with the LA4 in the system. XLR-2 is needed to drive the optimally drive the AHB2s in low gain, my processor cannot do this.

Fundamentally, this seems like a good Covid project to add some discrete commanded even if not present on the Benchmark remote.
They could also allow D1 - D4 to be mapped to XLRs in the setup which makes the existing remote (and codes) useful.

I spoke with Benchmark and the sales team gets it...

- Rich

Ok so I joined the forum after being a long time lurker to ask a question many have asked: will the HPA4 or LA4 be made available with discrete input codes?

Considering one of the other (still not sure if there is any difference when driving an external amp) but this is a potential deal breaker for my family.

Spoke to a very nice gentleman at Benchmark today who builds these things but didn’t even think to ask as it never crossed my mind it wouldn’t have discrete remote input codes. Hate to be foiled by this after all my research and listening.

Thanks,

Rich S.

Update: Another good discussion with Benchmark…..unfortunately, still no discrete input codes. Will have to mull that over.

In the meantime, LA4 or HP4 is the next question. Benchmark assured me there would be no compromise on measured or audible performance between the two but I can’t help but wonder if the addition of the headphone amp might result in some audible differences.

 

[ObjectiveSubjectivist]

It seems like 1/4 and XLR headphones outs are identical?
It's just a matter of convenience?

 

[richsto]

It seems like 1/4 and XLR headphones outs are identical?
It's just a matter of convenience?

Likely lots of opinions here but theoretically the XLR out should provide better performance. They likely both sound great, I am about to find out.

 

[ObjectiveSubjectivist]

Likely lots of opinions here but theoretically the XLR out should provide better performance. They likely both sound great, I am about to find out.

But it's only due to better contacts that XLR socket provide.
Whole topology is the same, as far as I know.
@John_Siau is that right?

 

[richsto]

HPA4 arrived three days ago and has been “settling” in. I just sat down for some more critical listening and wanted to share initial impressions. It’s matched with a Parasound A21+ Halo amp and Thiel 3.6 speakers. Sources are an OPPO UDP-205 (SACD), Cambridge CXN (Hi-rez), and a highly modified Music Hall CD25.2 (Redbook CD).

All the reviews regarding great transparency, timing/PRAT, detail retrieval and resolution etc are spot on so I won’t regurgitate. I was worried about a cooler analytical sound signature which would not be welcome with the Thiels. Pleasantly surprised that this was not entirely the case.

Turns out my aging Musical Fidelity A3.2CR single ended preamp, which is quite excellent, imparts a very slight warmth which (I know not the accurate truth) I’ve come to appreciate with the Thiels.

The HPA4 does not demonstrate any such deviations….which can be a good or bad thing depending on your perspective and/or preference. As I listen, I am awed by the transparency and “rightness” to the sound and each unique recording space and mic placement is both obvious and evident.

That said, I’m still reserving judgment on the HPA4 in my system. The only miss is that it seems to fail to consistently and routinely draw me in to the music - something I might attribute to the slight warmth of the Musical Fidelity pre I’m used to. Perhaps it just needs a bit more run in time, or perhaps I need to quit being so analytical and just enjoy the music.

More time will tell but what I can say is the HPA4 is one terrific engineered and superb sounding preamp.

Rich S.

 

[Soria Moria]

View attachment 239053View attachment 239054View attachment 239055View attachment 239058View attachment 239060HPA4 arrived three days ago and has been “settling” in. I just sat down for some more critical listening and wanted to share initial impressions. It’s matched with a Parasound A21+ Halo amp and Thiel 3.6 speakers. Sources are an OPPO UDP-205 (SACD), Cambridge CXN (Hi-rez), and a highly modified Music Hall CD25.2 (Redbook CD).

All the reviews regarding great transparency, timing/PRAT, detail retrieval and resolution etc are spot on so I won’t regurgitate. I was worried about a cooler analytical sound signature which would not be welcome with the Thiels. Pleasantly surprised that this was not entirely the case.

Turns out my aging Musical Fidelity A3.2CR single ended preamp, which is quite excellent, imparts a very slight warmth which (I know not the accurate truth) I’ve come to appreciate with the Thiels.

The HPA4 does not demonstrate any such deviations….which can be a good or bad thing depending on your perspective and/or preference. As I listen, I am awed by the transparency and “rightness” to the sound and each unique recording space and mic placement is both obvious and evident.

That said, I’m still reserving judgment on the HPA4 in my system. The only miss is that it seems to fail to consistently and routinely draw me in to the music - something I might attribute to the slight warmth of the Musical Fidelity pre I’m used to. Perhaps it just needs a bit more run in time, or perhaps I need to quit being so analytical and just enjoy the music.

More time will tell but what I can say is the HPA4 is one terrific engineered and superb sounding preamp.

Rich S.

Beautiful setup! Sorry to say, but more run time isn't going to change the amplifier.

 

[richsto]

Beautiful setup! Sorry to say, but more run time isn't going to change the amplifier.

Well the pictures make it look nicer than it is but thanks.

Mulling over my options but have a lot more listening to do - leaning towards keeping the HPA4 but it has to be a good match.

 

[ShiZo]

Very curious what multitone would look like

 

[enricoclaudio]

Kinda late to the party but today I ordered the Benchmark HPA4 so by Friday will be joining the Benchmark crew I'm going to use the HPA4 as headphone amp and pre amp/monitor controller in my home studio. It will be replacing a Drawmer CMC3 monitor controller which I'm currently using as pre amp/monitor controller as well. It my also replace my Topping A90D as makes no sense to have two top of the line headphone amps on my desk.

 

[Doodski]

Kinda late to the party but today I ordered the Benchmark HPA4 so by Friday will be joining the Benchmark crew I'm going to use the HPA4 as headphone amp and pre amp/monitor controller in my home studio. It will be replacing a Drawmer CMC3 monitor controller which I'm currently using as pre amp/monitor controller as well. It my also replace my Topping A90D as makes no sense to have two top of the line headphone amps on my desk.

This is out of my system's range but it sure is a pretty unit. That display is going to be wonderful to use and ogle.

 

[enricoclaudio]

UPS….. Really???

 

[_thelaughingman]

UPS….. Really???

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View attachment 258126

Ugh PS

 

[Sal1950]

UPS….. Really???

A bummer for sure.
But rumor has it there's been a bit of snow on the ground. LOL

 

[enricoclaudio]

Well, surprisingly enough, UPS rushed it and it's now "processing at destination" and rescheduled delivery for today

 

[enricoclaudio]

UPS..... Did it AGAIN!!!

The UPS truck did not show up and it was marked as 1st Delivery Attempted... These UPS drivers have no shame. I have 3 cameras that show no UPS truck has entered the apartment complex the whole day..... Well, 2 more days wait.....

 

[enricoclaudio]

HPA4 in the house

First impressions:

As a pre amp, which is the main reason I got it, all I can say is that I have depth regrets for not purchasing it long time ago. Compared to my Drawmer CMC3 monitor controller, the CMC3 sounds like a toy. As a pre amp, the HPA4 is TRANSPARENT, period. Do I hear differences between the HPA4 and the CMC3, of course I do. As a headphone amp, compared to my Topping A90D, honestly, I can't hear any difference. Both sound exactly the same to me. Both drive my H660s and Sundaras effortless. The HPA4 is going to stay for sure. 2 hours only since started playing with it and I love it.

Pink Panther is happy too

 

[Doodski]

HPA4 in the house

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First impressions:

As a pre amp, which is the main reason I got it, all I can say is that I have depth regrets for not purchasing it long time ago. Compared to my Drawmer CMC3 monitor controller, the CMC3 sounds like a toy. As a pre amp, the HPA4 is TRANSPARENT, period. Do I hear differences between the HPA4 and the CMC3, of course I do. As a headphone amp, compared to my Topping A90D, honestly, I can't hear any difference. Both sound exactly the same to me. Both drive my H660s and Sundaras effortless. The HPA4 is going to stay for sure. 2 hours only since started playing with it and I love it.

Very pretty setup! That HPA4 is looking pretty nice there.

 

[enricoclaudio]

Questions for HPA4 and LA4 owners. I setup my HPA4 on Auto-ON and plugged it into a Lutron Caseta Weatherproof Outdoor Smart Plug which I control with a Caseta Pico Remote or with the Lutron Caseta app. It works great because after going to bed, as soon I turn all the lights OFF for the night, the HPA4 turns OFF as well. Then in the morning, as soon I wake up, I turn my lights ON and the HPA4 turns ON as well. I asked Roy abut doing this and he said it was OK as long as Auto-ON was enabled. He also said that is was OK to leave the HPA4 ON 24/7. What do you guys do? Second question, regarding the display. Do you guys use the Display Sleep Timer or leave the Display ON all the time?