• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Review and Measurements of Benchmark HPA4 Headphone Amp/Pre

RichB

Major Contributor
Forum Donor
Joined
May 24, 2019
Messages
1,780
Likes
2,377
Location
Massachusetts
I am also waiting for this feature for almost 2 yrs now.

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
 

MattHooper

Major Contributor
Joined
Jan 27, 2019
Messages
4,065
Likes
6,422
Here is the icing on the cake:
Relay attenuators and gain controls normally cause clicks and pops in the audio while they are being adjusted. In contrast, the relay closures in the HPA4/LA4 are precisely timed into a make-before-break sequence that prevents pops and clicks. This system is so effective that we were able to include a soft fade and unfade when the -20 dB dim is toggled.

The -20dB "dim" function is something I've really grown to appreciate with the LA4. I've found it surprisingly useful the way it dims the music immediately to a still audible background (often enough a family member will enter my listening room to chat so I engage it, and if I just want to lower the volume to background for a while for various reasons, that single button up and down is really handy).

It's the feature I miss on the remote when I switch back to using my CJ tube preamp sometimes.
 

Tks

Major Contributor
Joined
Apr 1, 2019
Messages
3,164
Likes
5,240
The -20dB "dim" function is something I've really grown to appreciate with the LA4. I've found it surprisingly useful the way it dims the music immediately to a still audible background (often enough a family member will enter my listening room to chat so I engage it, and if I just want to lower the volume to background for a while for various reasons, that single button up and down is really handy).

It's the feature I miss on the remote when I switch back to using my CJ tube preamp sometimes.
I can attest to this, though it comes by way of the RME ADI 2.
 

Endibol

Member
Forum Donor
Joined
Dec 18, 2021
Messages
48
Likes
70
Like all potentiometers, the pot in the DAC3 has some L/R imbalance at low volumes when passing an analog input. We have a L/R trimmer in the DAC3 that trims out the L/R imbalance in the upper half of the volume range, but below that point, the L/R imbalance will begin to increase.

With a digital input, the DAC3 volume control is a 32-bit digital control with 0.5 dB steps. The digital volume is controlled by sensing the position of the rotary pot. The digital volume control has near-perfect L/R balance and near-perfect 0.5 dB steps. The only limitation is that the digital volume control reduces the signal level without reducing the output noise of the DAC. Excessive use of the digital volume control will reduce the effective SNR of the DAC. If the DAC3 is connected to a consumer-grade XLR input on a power amplifier, the passive -10 dB pads should be engaged at the output of the DAC3.

In contrast, the HPA4 and LA4 preserve the SNR of the input signal over a wide range of volume settings. This is achieved without the L/R imbalance problems of a rotary pot. The HPA4 and LA4 have a L/R balance that tracks to better than +/- 0.2 dB over the entire 142.5 dB control range. And it does this in 0.5 dB steps. Needless to say, this requires very high precision resistors. Many are 0.01%.

All potentiometers also add some distortion. In the DAC3, the pot is not in the signal path when playing a digital input. When playing analog inputs on the DAC3, the pot is in the signal path but we keep that to a minimum by putting the pot inside a feedback loop while configuring the circuit such that there is no wiper current. Placing the pot inside a feedback loop also allows us to use linear-taper pots instead of log-taper pots. The linear pots can have better L/R tracking, and a lower total end-to-end resistance. Lower resistances contribute less thermal noise to the system (Johnson Noise). Nevertheless, the DAC3 pot does not come close to rivaling the lower noise and distortion of the relay-controlled volume in the HPA4 and LA4.

Here is the icing on the cake:
Relay attenuators and gain controls normally cause clicks and pops in the audio while they are being adjusted. In contrast, the relay closures in the HPA4/LA4 are precisely timed into a make-before-break sequence that prevents pops and clicks. This system is so effective that we were able to include a soft fade and unfade when the -20 dB dim is toggled.
@John_Siau
Hi John,
There is still one question I have: Does employing the -10 dB setting on the DAC3 reduce both signal AND noise level, therefore keeping the SNR the same as for the 0 dB setting (assuming the same volume knob setting)?
If this is the case I can improve the SNR of the DAC3 for digital signals by selecting -10 dB and have the volume knob further to the right (11 o'clock or more) for the same output level. Is my thinking correct? Thanks
P.S. Thanks a lot for your clear explanations on this forum and Benchmark's instructive and informative website! I don't know any other company with such level of transparency and honesty.
 
Last edited:

John_Siau

Active Member
Technical Expert
Manufacturer
Joined
Jul 17, 2018
Messages
141
Likes
1,185
Location
Syracuse, NY USA
@John_Siau
Hi John,
There is still one question I have: Does employing the -10 dB setting on the DAC3 reduce both signal AND noise level, therefore keeping the SNR the same as for the 0 dB setting (assuming the same volume knob setting)?
If this is the case I can improve the SNR of the DAC3 for digital signals by selecting -10 dB and have the volume knob further to the right (11 o'clock or more) for the same output level. Is my thinking correct? Thanks
P.S. Thanks a lot for your clear explanations on this forum and Benchmark's instructive and informative website! I don't know any other company with such level of transparency and honesty.
Yes, the passive -10 dB and -20 dB attenuators on the Benchmark DAC1, DAC2, and DAC3 converters lower the output signal and the output noise. If you add passive attenuation, you will need to rotate the volume control clockwise to achieve the same output level. If you can still reach your desired playback level with the pad engaged, you will achieve a better SNR. But, if you add too much attenuation, you may not be able to reach the desired playback level.

The LA4 or HPA4 are the equivalent of having a variable attenuator that can be set in 0.5 dB increments. At all listening levels, the DAC will be delivering its full performance and this in turn will be delivered to the power amplifier using the relay-controlled attenuators in the LA4 (or HPA4).
 

Endibol

Member
Forum Donor
Joined
Dec 18, 2021
Messages
48
Likes
70
Yes, the passive -10 dB and -20 dB attenuators on the Benchmark DAC1, DAC2, and DAC3 converters lower the output signal and the output noise. If you add passive attenuation, you will need to rotate the volume control clockwise to achieve the same output level. If you can still reach your desired playback level with the pad engaged, you will achieve a better SNR. But, if you add too much attenuation, you may not be able to reach the desired playback level.

The LA4 or HPA4 are the equivalent of having a variable attenuator that can be set in 0.5 dB increments. At all listening levels, the DAC will be delivering its full performance and this in turn will be delivered to the power amplifier using the relay-controlled attenuators in the LA4 (or HPA4).
Thanks John.
I selected -10 dB on my DAC3 and use the mid gain level on the AHB2.
This in combination with my Revel Performa F228Be (sensitivity 90 dB @ 2.83 V, 1m) allows me to play quite loud at volume settings around 12 o'clock. With the default settings (zero dB attenuation and low gain) the knob never needed be further than 10 o'clock to achieve loud playback levels.
 

sprellemannen

Active Member
Forum Donor
Joined
Jul 21, 2018
Messages
199
Likes
460
A nice looking desk setup (not mine) with the HPA4 and DAC3 B:
11222118.jpg
 

skhan007

Member
Joined
Dec 30, 2021
Messages
97
Likes
73
Location
Washington, DC, USA
Its worth every penny. Buy a new one and celebrate Christmas early this year.
I'm tempted! It's so strange to hear reviews and videos, where people state the exponentially lower priced THX and Topping offerings sound identical to the Benchmark HPA4. How can that be? The data/measurements on this are spectacular and I can't conceive how a tiny THX 789 "is just as good."
 

anmpr1

Major Contributor
Forum Donor
Joined
Oct 11, 2018
Messages
3,190
Likes
5,356
I'm tempted! It's so strange to hear reviews and videos, where people state the exponentially lower priced THX and Topping offerings sound identical to the Benchmark HPA4. How can that be? The data/measurements on this are spectacular and I can't conceive how a tiny THX 789 "is just as good."
When you get to this level of performance, buying decisions are not supported by raw specs anymore. Those won't matter. It's other stuff--who you want to give your money to, design language (look and feel), warranty, ease of service if you ever need it, how full your bank account is, and so forth.

I suppose there is a 'theoretical' limit as to the numbers that can be achieved, given the parts that are available. Will that threshold be reached? With any electronic item, price per performance ratio usually improves each couple of years. Benchmark DAC3 based products are what? --five years old, now? That's a long time in the world of audio design. But at five years old, you can't go wrong with one.
 

sprellemannen

Active Member
Forum Donor
Joined
Jul 21, 2018
Messages
199
Likes
460
@anmpr1 (and @skhan007)
and many more things can be added, including:
* reliability (there are a lot of reports on problems with hi-fi products from Chinese brands on this forum, and some of these brands seem to lack or have a "fake" CE marking as well),
* ease of use/functionality (a good remote control or volume knob, useful buttons/menus on the product, ...),
* connections (that is, inputs and outputs),
* build quality,
* extensive and good manuals (in Benchmark's manuals, measurements are included as well, and you easily find the manuals of retired products on their site as well: see support/manuals).

As a Benchmark products owner for 12 years (previously DAC1, now 2xAHB2 and DAC2 HGC), my experience with Benchmark is that the company is absolutely top class in all what @anmpr1 mentioned as well as all the things listed by me . Regarding CE-marking, I recently looked in Benchmark-product-manuals to see what is written there: In their manuals you find the photo of the CE certificate of compliance (look for instance at page 55 in the manual for HPA4), just another example of Benchmark being an exemplary company.

I have never had a single issue with my Benchmark gear, but have sent them some general questions about their products. All of them have been excellently answered (and quickly!). I want to thank Rory Rall at Benchmark for his outstanding customer support, and all the employees at Benchmark for their contribution in making their amazing products available for us. A big thumbs up for Benchmark!

a2.jpg
 
Last edited:

SoundGuy

Active Member
Joined
Aug 13, 2022
Messages
115
Likes
116
Like @sprellemannen and so many others, I discovered Benchmark with their DAC 1 - a long time ago - it is close to 20 years ago since I discovered this company. The DAC 1 was audibly better than anything else at the time. I believe the DAC 3 which is my reference for the last 5 years is still unbeaten but at least (finally after 20 years) competition is getting close. Back in the early days of DAC1 it was absolutely crazy how the DAC 1 made every other DAC sound like crap. Shocking how a hi-fi industry outsider (pro TV production equipment company) showed up the entire industry to be stuck in boxed thinking and old ways - all the legendary experts of our industry humbled at once (though they will never admit it).

I have continued to purchase other much more expensive devices over the years but after extended periods of trying to love these new far more expensive toys and wanting to believe in all the latest marketing hype, I always end up going back to Benchmark.

If you like reference sound (pure fidelity with warts and all that is glorious in a recording) then Benchmark is the reference product to go for. Supremely reliable. Unflattering to a bad recording but even so you will hear more truthfully the beauty of what the studio microphones actually picked up - only equaled but not improved upon by other product(so far).

@John_Siau has the humble open-minded engineering approach that has lead to once in a generation breakthroughs. He took widely available technologies like FPGA‘s, relays and metal film resistors and redesigned and repackaged them into solving problems plaguing an entire generation of audio equipment - like jitter, inter-sample overs, volume control, channel separation, power supply noise, limitations of commercial DAC chips and more. Credit to Benchmark company for believing in John. The actual story of Benchmark appears to be similar to the book “Elephants can’t dance“ where IBM had to reinvent itself in the face of technology/industry evolution - and survive by finding a new market for their engineering skills.
 

Martin

Major Contributor
Forum Donor
Joined
Mar 23, 2018
Messages
1,432
Likes
3,604
Location
Cape Coral, FL
I am absolutely intrigued by the HPA4. If anyone had a lead on a pre-owned one, please let me know.

I kept a search running on eBay. I was tripping over myself buying one in mid-July that popped up for $1700 (with remote). I thought it was reasonably priced at $3099 new, at $1700 used it was a true score.

Martin
 

skhan007

Member
Joined
Dec 30, 2021
Messages
97
Likes
73
Location
Washington, DC, USA
I kept a search running on eBay. I was tripping over myself buying one in mid-July that popped up for $1700 (with remote). I thought it was reasonably priced at $3099 new, at $1700 used it was a true score.

Martin
Yeah, I saw that one! I had a saved search on eBay and when I got the email alert that an hpa4 was posted, I went to eBay and it was sold. Apparently, to you!
 

Sal1950

Grand Contributor
The Chicago Crusher
Forum Donor
Joined
Mar 1, 2016
Messages
11,136
Likes
12,254
Location
Central Fl
Yeah, I saw that one! I had a saved search on eBay and when I got the email alert that an hpa4 was posted, I went to eBay and it was sold. Apparently, to you!
Two types of folks in this world.
The quick, and the dead. ;)
 

anmpr1

Major Contributor
Forum Donor
Joined
Oct 11, 2018
Messages
3,190
Likes
5,356
As a Benchmark products owner for 12 years...
In my archive slumming I came across a company called (doing this from memory) Benchmark Sound Systems, or something like that. I'd have to dig deep, but I think they were a pro oriented company, however I don't remember exactly what they were selling. This was back in the late '70s and '80s. I don't know if it was an early iteration of Benchmark Media Systems.

The first I ever heard of them was from Peter Aczel, who owned the DAC-1. Later, DAC-2. He told me that he didn't think the 2 was 'audibly' better than the 1, but as a gearhead he had to have it, because of the numbers. When the 3 came out, I sent him a note about it, not having heard from him in a while. It was when I found out he was quite ill, shortly afterwards, passing.

Once it was time to upgrade, I bought a 3 and AHB, mostly because of his reviews, and really in his honor, since I learned so much from him. At this point, I can't imagine ever upgrading either the DAC or the amplifier. Ever.
 

Sal1950

Grand Contributor
The Chicago Crusher
Forum Donor
Joined
Mar 1, 2016
Messages
11,136
Likes
12,254
Location
Central Fl
The first I ever heard of them was from Peter Aczel, who owned the DAC-1.
Few have had as positive influence on audio as Peter.
We can now add Amir to that short list. ;)
 
Top Bottom