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Benchmark Audio DAC3 DX and AHB2 amplifiers Review

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“In a class of its own”

HiFi enthusiasts know their classes of solid state amps, the most commonly used ones being Class A behemoths that tend to run hot, Class A/B solid state designs that tend to run cooler and often yielding more watts per dollar, and Class D, or Switching (chip) amps, which are even less expensive and debatably offering higher performance precision. Enter Lucasfilm Ltd., known to seasoned film fans as the company founded by filmmaker George Lucas, who hired audio scientist Tomlinson Holman to revamp the audio chain in movie production from the set to the theater. The result was a certification program of standards called THX (trademarked) that was used for the first time in the production of “Return of the Jedi” in 1983.

Fast forward nearly 35 years later and we have Benchmark Media Systems, a HiFi component maker with one foot in the pro audio world and the other in the domestic sector of HiFi, collaborating with the THX program to make a new class of amplifier designated Class AAA. The “AAA” stands for Achromatic Audio Amplifier, an analogue amp that greatly reduces energy consumption. Some highlights of this technology include the use of both feedback and feed-forward error correction, accomplishing an almost non-existent distortion level of 0.0001% at 1kHz, greatly reduced power supply-induced distortion and noise, and a resultant signal-to-noise ratio (SNR) in excess of 132 dB A-weighted.

In terms of operational efficiency, rather than reducing the bias current, which typically has the effect of increasing crossover distortion, THX technology claims to allow high biasing while practically eliminating crossover distortion, and doing so with lower power consumption. Tracking Power Supplies that deliver power “on demand” usually introduce their own distortion, but THX’s AAA technology renders this negligible. The outcome is a seemingly perfect audiophile amplifier: Light with a small footprint, has the ability to drive demanding loads to full output with extreme integrity, has vanishingly low distortion and runs cool.

Benchmark Audio’s promotional brochure enthuses about the SNR ration in its discussion of the collaboration of Benchmark and THX, “… this is 30 dB greater than most amplifiers. That’s 30 times less noise than typical amplifiers – the perfect amplifier for a high-resolution audio playback system.” The Instruction Manual states, “132 dB is approximately equivalent to the noise performance of a perfect 22-bit digital system… At high output levels, the AHB2 [amplifier] remains virtually distortion free while driving heavy loads.” I translate that as, “We dare you to put this amp on the King Sound King III electrostatic speaker and give it a good run.” Better yet, I’ll do that as well as put the amp with the shockingly revealing PureAudioProject Trio15 PAP Horn 1 Speaker.

Supposedly, Star Wars (trademarked) has made your stereo amp better. The “THX Force” is with us audiophiles in the AHB2. When you conclude reading this assessment you will know whether I conclude Class AAAis aforce or a farce.

More settings than Star Wars installments

How many settings on a component does it take to make you happy? To arrive at an answer consider the two schools of component building; the first offers only one setting, one option for the sound, the other offers several settings and a variety of options for the sound. For the moment, putting aside the inherent differences between classes of amps, which is better : A monoblock design, or a much more involved design that offers modes such as Stereo, Mono, XLR and Neutrik outputs, and a gain setting selector? Your preference says much about you as an audiophile.

Over the years, I have careened back and forth on this question in regards to all components, even speakers, as there is a diversity of opinion among manufacturers in their products. It should give pause for consideration that there is no complete universal perspective in manufacturing, nor in listening, when it comes to the best sound produced by feature-poor or feature-rich components. There is a veritable chasm in the audio landscape today, on the one side featuring refreshed throwback designs, and the other displaying amps with digital management, onboard DACs and in some cases even room correction modes, to say nothing of systems with active multi-channel processing for stereo.

I recall my ten-band analogue Audio Control Equalizer that saw vigorous use, portending my development into a system builder exploring permutations of HiFi systems. It must have been more than 30 years ago when I first heard an audiophile authority say equalizers were not to be included in high-end systems. I thought it a stupid comment at the time, for how was a person to tailor their sound if not for all those channels of frequency control? Not too many years later, due to exploration of more streamlined systems, I reversed my opinion and concluded the same; the simplest signal path is the best. Yet, time and again as I built systems I encountered exceptions to that rule. Regularly, rigs that were not the simplest could attain a more gratifying sound. It wasn’t as simple as the straight-wire-with-gain principle suggested. That seems the case with components, even amplifiers, as well. Thus, the simplicity/complexity pendulum continues to swing over time.


“Night and day” difference

Currently, I have two sets of components, DACs and amps that represent the proverbial night and day difference from each other in terms of design. The simpler components are the Exogal Comet DAC and the Belles ARIA Mono Block Amplifiers, while the more complex components are the Benchmark DAC3 and the Benchmark AHB2 Amplifier. I say, simpler or complex with no implication or suggestion on  any enterprise of whether their process of building any audio component is simple or not. I am reminded of the misnomer in Darwinian circles of calling a lower life form “simple”. There is no such thing as simple life. When in terms of complexity, a single celled organism, much less a strand of DNA, makes a supercomputer seem like an abacus, it’s never simple. Such simple life, as it is called, is lower than more advanced creatures but by no measure, literally when it comes to the statistical improbability, is it simple enough to just happen.

In referring to components as “simple” versus “complex” I am discussing the complexity of features of the design, that is, how many options for use are offered. This review is about the Benchmark products and will be discussed in the context of how strikingly feature-laden they are. The multi-faceted operation of the Benchmark DAC3 and AHB2 will be considered as how they may assist with building superior systems.

Which is better in terms of performance? Which assures the best outcome in system building? While this is one comparison of an endless range of possible comparisons, it will stand as an example to show the considerations involved in selecting an amp and the expected sonic outcomes. This begs the question; does the massing of features detract from the sound in comparison to more streamlined competitors?

The Belles ARIA Mono Block Amplifiers, also in for review, are representative of a simpler design principle. The ARIA has – get ready for it – a power button, one pair of RCA inputs, one pair of speaker terminals, and a 15A IEC port with fuse holder. That may have been a bit much to take in all at once, so let’s examine it. The ARIA has one signal path option only. You get no derivative, no options, no “second chances.” I have found that in system building, second and third chances in the form of alternative configurations are very helpful to attainment of pleasing, but not necessarily the most accurate, performance. In the case of a component with only one operational mode, it had better be astounding, because it gets one chance to impress.

We can apply the same discussion and questions to comparison of the Exogal Comet, previously reviewed by myself for Dagogo, and the Benchmark DAC3 DX. The Comet truly is a one-outcome DAC; whatever signal you feed it, the DAC formulates a parallel signal and forwards that to the amplifier. As with the ARIA, the Comet produces a consistent result, one chance to impress in any given system. Alternatively, the DAC3 DX has several adjustments allowing conditioning of the signal. 

What good is configurability? The Benchmark DAC3 DX and AHB2 Amplifier can fail to be optimized several times through selection of less than ideal settings and still have the potential to come out on top. The pertinent question, then, is whether they may be so, attaining the caliber of an amp with a dedicated signal path and a DAC with an algorithm that is agnostic to the incoming signal. Let’s find out.

DAC3 DX rear panel

The Owner’s Manuals are available – all 117 pages of them

I used to attempt thorough explanation of manufacturers’ Owner’s Manuals in my reviews. The longer I am at the reviewing game and the more information is found online, the less inclined I am with the time I left in life to rehash a Manual in a review. I recall reading reviews years ago and scoffing at the imprudence of the reviewer who said, “Consult the company website…” Now, I consider that recommendation a stroke of genius; I just saved myself a few hours!

However, I will summarize the notable features of the DAC3 DX:

3:1 summing on the main outputs. The ES9028PRO [DAC chip] is an 8-channel 32-bit converter. Three channels are summed for each of the stereo outputs, while the remaining two channels provide the auxiliary outputs. (Note: If you hook up your amp to the Auxiliary outputs you will not be getting the best processing of the DAC3 DX!) Harmonic compensation is the name given to the ESS chip’s capacity to remove most 2nd and 3rd harmonic distortion of the D/A converter.

High Headroom Digital and Analogue Processing prevents clipping of inter-sample overs (see Instruction Manual for further details). 

High Efficiency, Low Noise Power Supplies 

UltraLock3 Clock System provides outstanding jitter attenuation.

Asynchronous USB Audio 2.0 supports DSD and 192 kHz, 24-bit PCM

32 Bit Digital Gain Control uses a motor-driven volume control to set the gain of a 32 bit dithered digital gain control, “The volume control is a servo-driven analogue potentiometer… produces a DC voltage that controls the gain of a dithered 32-bit multiplier. The outputs of the multiplier drive the 32-bit D/A converters.”

Native DSD Conversion accepts incoming DSD signals via the USB or Coaxial inputs. The signal is routed to a bank of 1-bit DSD D/A converters. Three balanced 1-bit converters are summed together for each of the MAIN outputs.

1W Amp Crossover Distortion

For those who want something technical to chew on in regard to the amp, the Appendix of the AHB2’s Instruction Manual contains two pages of dense, technical discussion. Here are some highlights: There are two amplifiers inside the chassis, a Class H, and a Class A/B with feed forward error correction, “Each channel of the AHB2 is equipped with a main amplifier and an ultra-clean low-power auxiliary error-correction amplifier.” The A/B amp does the bulk of the work, while the auxiliary amp provides a low power error correction signal. The error-correction amp actively drives the output as the A/B amp transitions between push and pull states. Crossover distortion associated normally with A/B designs is all but eliminated. Multiple power supply rails and tracking power supply rails are used in the design, and along with the feed-forward error correction they do not produce significant distortion as in most A/B amps. In addition, a switch-mode power supply is used with switching frequencies above the audio band, and in lieu of stored energy in capacitor banks, Benchmark seeks to nearly eliminate all storage after the power supply. Power supply regulation takes the place of energy storage, causing the amp to respond quickly to peak loading, and makes it immune to AC line voltage fluctuations. The AHB2 also has a digital monitoring system that monitors all critical functions, providing comprehensive protection from overload and fault conditions.


VAariants of the DAC3

There are three variants of the DAC3:

DX under review (only digital inputs; 2 Toslink, 2 Digital Coaxial, 1 USB and 1 AES/EBU input; two pair RCA outputs and 1 pair XLR outputs; two front headphone outputs);

HGC (2 pair Analogue inputs, 2 Digital Coaxial inputs, 2 Toslink inputs, 1 USB input; 2 pair RCA outputs, 1 pair XLR outputs; two front headphone outputs);

L (same as HGC, but without the twin front headphone outputs).

Study the features carefully, as the units are similar but different in potentially critical ways in terms of setup of systems. You do not want to order one of them only to find that down the road you are limited in setup, i.e. ordering the model without headphone outputs.  For instance, am I taking a risk by using the DAC3 DX that I will not need analogue inputs? Yes, however, I have fallen into the habit of not adding a preamp to the signal path if I use a DAC having an integral volume control. That would result in duplication of gain stages, which typically muddies the system sound.


Cramming in all the functions

In terms of user-friendliness, Benchmark and Nagra may have a competition on which company can jam the most features into the smallest component. The only other DAC I have used that is so cramped is the iFi Micro DAC, and it is portable. Forget trying to spy the functions indicated by the blue LEDs on the face of the DAC 3 DX from your listening position, just memorize where those LEDs are. Learn also the flashing patterns of the LEDs and you will be fine in terms of daily use.

The speaker connection posts are not very practical. I hate the encapsulated posts that are becoming popular, forcing entry by spade terminations from underneath. I get it, more protection against spades slipping and potentially causing a short. But if the speaker cables have stiff, long leads – and many do – it’s a PITA. Benchmark has allowed little leeway between posts, inputs and switches. Must studio wonks attempt to cram everything into one inch? I have been in a few studios around the world and many have precious little room, so I get the idea of space saving designs. Home users should expect a touch of frustration with hooking up leads. Get used to it, as it’s worth it. When it’s put together you will forget all about it.

If the DAC3 DX doesn’t work in your system, you likely set it up wrong. I couldn’t get a signal out of it at all when I first fired it up, even though Tidal and ROON were synced perfectly. Well, almost perfectly. I surmised that any product with 75 pages of instructions might have a setting I was overlooking. Sure enough, it was set to receive USB 1.0, not USB 2.0, the current standard. A push and hold of a button, followed a few LED flashes I should memorize, and I was up and running. It should be said that incorporating the DAC3 DX with ROON and Tidal was the most trouble free setup of any DAC I have ever used, and it has been flawless in terms of operation. Some DACs I have used needed a series of starts and restarts to get the Salk StreamPlayer III, Tidal and ROON to interface permanently, but the DAC3 DX has presented no problems in that regard even when pulled out and reinserted into the system.

Manufacturers such as Benchmark and Exogal know a great many audiophiles despise diminutive indicators, yet they keep building them. Exogal does so to nudge users toward controlling their products with tablets or smartphones, while Benchmark caters to studios as well as domestic users. When the DAC3 DX sits three feet from you, the layout is obviously smart. It is a case where Benchmark builds for the pro market and also sells to the audiophile market. If the appearance and a traditional aesthetic steers your spending habits, then the Benchmark DAC3 DX is not for you.

10 Responses to Benchmark Audio DAC3 DX and AHB2 amplifiers Review

  1. Shahed says:

    Thanks for your detailed and informative review Doug! I’m currently driving my PAP Horn1 with First Watt J2 amplifier. This pairing was inspired by your review 🙂 I’m using Allnic L3000 mk2 with great success with J2 amp. Allnic has very low output impedance and hence suitable for any SS amp.

    If you are forced to pick a favorite between Benchmark AHB2 and First Watt J2 driving the PAP Horn1, which one would you pick? This is assuming Benchmark DAC is not in the chain and some tube preamp is present before the amp.


  2. Douglas Schroeder says:

    God’s Peace,
    Thanks for the comment; it’s good to know that I inspire at least one audiophile globally. 😉

    Honestly, I like both amps quite a bit. It’s tough to not like an amp driving the Horn 1! The J2 has less dynamic power, less forward and “punch” to the sound, while the AHB2 is very, very tight, clean, and more forward and more “punch” dynamically. The tonality is pretty close between the two of them.

    The most significant difference would be the sense of space and air in the venue; the J2 would seem typically like a larger space, and the AHB2 would seem more studio-like, not in an absolute, but relative sense. The speaker would sound more laid back with the J2 and more aggressive with AHB2.

    Take your pick!


  3. Doug,
    In your opinion, how would the Mono or stereo ABH2 get on with the Sound Labs U-545s (nee’ U4iAs) that you reviewed?

  4. Dan Piekarski says:

    Hello Doug,
    Thank you for the very thorough and detailed review of the Benchmark AHB2 components!

    I have read your reviews that go into a high level of detail on both the Benchmark and Legacy Audio products and therefore am asking for your opinion on a somewhat unique audio situation.

    In re-configuring a Home Theater configuration I am considering in using a pair of Vandersteen 2CE speakers for the rear surrounds in a 7:1:4 Atmos set up.

    The Front end has 2 Legacy Focus SE mains, 1-Legacy Marquis XD center, supplied by a Legacy Power Bloc4 amplifier. Upstream from that is an OPPO player and Integra DRX-R1 receiver…
    We split 50/50 time on 2 channel music and Home Theather.

    My question regards the Amplification for the Vandersteen 2CE rear speakers, as they efficiency is rather low at 88 db, and impedance ranges from 7 ohms nominal to 4 ohms minimum..

    Doug, based on your knowledge of both product lines which amp would you choose between the Benchmark AHB2 and the Legacy Power Bloc to drive the Vandersteen 2 CE speakers? The Legacy delivers 325 Watts into 8 Ohms, 650 Watts into 4 Ohms. But the Benchmark performance reviews have been exceptional.

    Any feedback/direction that you can provide would be much appreciated!
    Thank you !

  5. Dan,
    God’s Joy to you,

    Thank you for the complement; it is gratifying when people find value in my reviews.

    You ask a question that does not have a direct answer. Either of the amplifiers would do a commendable job in driving the Vandersteens. I have done as you, in that my surround speakers are different than the mains. In my audio world HT is not THAT important (That is heresy to some who consider HT their primary source of entertainment). I suspect that value and flexibility are large considerations as you are willing to mix gear for HT.

    As such, the answer is not a simple this or that amp. The cleanness, tonality, dynamers, etc will all vary between the two amps with the Vandersteens. I could happily recommend either amp as I think they are more similar than different. They both have excellent detail retrieval and plenty of dynamic power. The PowerBloc is one class D I would recommend.

    I think you potentially have your answer in hand. Why not try the PowerBloc amp you have with the Vandersteens and see if it is suitable to you. Unless you are trying to wake the dead with levels, you won’t have any issue with that amp in driving the Vandy’s. If something is niggling, bothering about the sound, then do a trial of the Benchmark.

    One off topic recommendation; if the Oppo is your primary source, I strongly suggest you look into a music server and streamer like the Small Green Computer sonicTransporter and SONORE Signature Rendu SE with systemOPtique that I reviewed. The sound quality is sensational and convenience off the charts. I think you may find yourself listening to music much more with such a source. Personally, I do not feel that extreme expenditures are necessary in HT, as the visual stimulation seems much more important, i.e. video quality. Again, others may disagree.

    My advice is based on the perspective that functional, good enough performance for HT is a legitimate goal, as more than 90% of my investment and effort goes to 2 channel. You may feel that this is not good guidance, so I encourage you to discuss with others, too.

    Douglas Schroeder

  6. Dan Piekarski says:

    Hello Doug,

    And thank you for your pleasant reply.

    I will reconfigure the system and give that a try as you recommended. That should help rule in or out the Legacy amp. Was also able to make the trip to the Legacy plant in Springfield and they are great people to deal with.

    Read your review of the Legacy Focus SE speakers with the wavelet processor, and that may be an addition someday, but for now the Focus SE’s are very enjoyable to listen to. Currently listening to Acoustic Alchemy in 2 channel and the instrumental sound through the Focus SE’s is a real treat for me.

    I agree that the HT world is not that critical as the sound does vary quite a bit with the various video /audio sources. We enjoy family movies and having a good front end speaker system helps even more. Two very good sounding Atmos movies were the J K Rowling based Fantastic Beasts movies, and the Iron Man movies had some good sound for a Blue Ray only action movie.

    For Home Theater , the Legacy Marquis XD center channel speaker is best center channel that I have heard/owned, and the SVS Ultra 13 Subwoofer helps fill in the bottom end.

    My theory is to have a very good 2 channel system and using it for Home Theater is an extra bonus.
    Some folks do have heartburn with HT but it works very well for our family.

    Also Doug, your recommendation for the music streamer and server is very timely. I have printed your reviews and will reread them and highlight the key points. I also printed the info for the 2 components that you recommended. Having the equipment and setup to listen to high quality sound with almost unlimited titles is very appealing to someone who remembers 8 tracks and cassettes! (Haha, what on earth are those!)

    Honestly I am pretty uneducated in the world of digital, PC audio, servers and streamers. I was fortunate enough to attend Axpona the past 2 years and met Dr Aix, Mark Waldrep and bought his book and also got the book from Jim Smith called Get Better Sound.

    There are many components in that area and I have much to learn in that area. Part of the fun of Audio is the research into the various options and listening to equipment choices.

    With the weather changing and golf season winding down, audio research and education is a perfect fall/ winter hobby for me.

    If you have any other entry level advice or recommendations for the music PC/ Streaming / Servers/ DACs, etc it would be greatly appreciated!

    Thank you Doug for all of the hard work that you do!

    Dan Piekarski

  7. Dan,
    God’s Joy,

    Thank you for the encouragement and compliments; I appreciate it!
    Glad that my comments were helpful. I’m still stunned at how good the systemOptique converter from SONORE is at eliminating digital noise and allowing minutia in the music to shine through.

    Feel free to stay in touch in regards to the build out of the system.

    Douglas Schroeder

  8. Hello Doug,

    Hope that you are well.

    Just to follow up , I did take your suggestion, and wanted to provide some feedback!

    I positioned the Vandersteen speakers directly next to the Legacy Focus SE speakers and listened to some very familiar tracks on the Legacys. Next I switched the Legacy Amp source to the Vandersteen speakers and played the identical tracks several times.

    I was totally amazed at the sound coming pout of the Vandersteen speakers! Obviously I had to very slightly adjust the volume for the less efficient speakers but once tweaked in, I have to admit that those speakers have never sounded so good!
    Thank you for your suggestion!

    I did order the Legacy Power block amp and just got it in the mail this week, and am looking forward to hooking it all up!

    I appreciate your thoughts on the Sonore system and am still looking in that direction next.

    An area of interest recently in music streaming is in the one box solutions and a couple of good quality brands I have been studying are the Lumin T2, and D2 and also the Bryston BDA 3.14 , and the Mytek Brooklyn streamer is also highly regarded.
    Do you have any opinion or strong thoughts on these components?

    I have a simple recommendation for you also, as my wife listens to some music on her desktop and I Pad device in the kitchen. One speaker model that I recently purchased for her was the Vanatoo Transparent Zero. I heard those at the Axpona show and they are awesome little speakers for a desk top..

    Doug, Tank you again for your recommendation and feedback!

    Take Care!


  9. Dan,
    God’s Peace,

    I’m elated that the suggestions are working out for you. A bit of curiosity and experimentation can lead to a holistic improvement and much more enjoyment.

    I cannot comment on the sources you mention, as I have not used them. I have heard the Booklyn at a friend’s house and it performed well.

    It has been a long time since I did any desktop sound. I normally do not listen to music while on computer. I appreciate the lead, however.

    Douglas Schroeder

  10. James Romeyn says:

    I too thoroughly enjoy Doug’s reviews and find much value in them. Doug seems like someone who is eminently capable in writing user manuals for the most complex machines.

    Upon request I’ll add a detailed room/system description. Suffice to say I’m in my late 60s, a lifetime music/high-end audio business professional, the room and system are refined and revealing of changes in any cable, program or component. The room is well treated, moderately lively and NOT overdamped. The system employs at least 2 professionally designed proprietary pieces: one is a huge server/streamer with ca. 4x the power of Chord’s powerful M-Scaler, the other being a discrete passive (or active) accessory speaker solely for reverberant field energy. One of Doug’s favorites, Clarity Cable is used throughout but not quite exclusively. The system employs a state-of-the art distributed subwoofer array, an improved version of the system that TAS awarded 3 Golden Ear Awards. HP cutoff is ca. 55 Hz.

    Main speaker voltage and current requirements in this room: The main speaker is a 2-way satellite with natural rear-ported roll off ca. 55 Hz, true 90.5 dB, 9/6-ohm nominal/minimum, benign phase angle, IOW well above average on the easy to drive scale. Maximum power w/20 Hz input (below the port tuning F where the proprietary pro-sound mid-bass is unloaded) is ca. 100Wrms. Ca. 110 dB maximum clean output w/only 1 dB of dynamic compression (a constant directivity system w/proprietary wood waveguide and 1″ beryllium compression driver.)

    Coincidentally both tested amps rated 100W @ 8-ohm. (I have a 3rd amp rated 140W @ 8-ohm which did have more punch and dynamic prowess; that advantage was most audible in the mid-bass range.)

    3 persons participated in a level-matched AB test between Benchmark’s AHB2 and Atma-Sphere’s Class D mono blocks. (One amp, cannot recall which one, required .5 dB input level change which netted ca. a negligible .1 dB output difference. To eliminate sub level differences, we simply turned off the sub array.) Note the main speaker cutoff is ca. 50 Hz.

    Both amps sounded tonally neutral.

    All agreed AHB2 sounded more “accurate” and revealed a little more musical detail that the Class D could not dig out of the mix.

    But overall, all 3 preferred the Class D, with increased density of images, a larger stage in all 3 dimensions and significantly more musical flow and emotional involvement. I would say the above advantages were in equal proportion, but if I had to pick one, the density advantage might have been the biggest. Think of the best qualities of the best OTL tube amps but without the heat and maintenance.

    The Class-D provided a performance upgrade at least equal to its 80% higher SRP. Both amps are US made and would likely reflect similar price discrepancy wherever they are both sold.

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