Benchmark Audio DAC3 DX and AHB2 amplifiers Review

Aesthetics and build

There is not much to say for the aesthetics of Benchmark products except that they are tidy, studio worthy in appearance and diminutive. They also, mercifully, are lightweight. One can carry the stack of all three together and not suffer a hernia, which is worth considering in a community of aging audiophiles. Benchmark offers silver and black facades on the DAC and amp.

The build of the DAC3 DX and AHB2 Amps is sufficient but not ultimate. The casework on the DAC3 DX is not robust enough to confidently lean a hand on while placing cables, but the amps are tougher. The DAC3 DX is so light that when I connected the Clarity Cable Organic XLR Interconnects their tension from their stiffness lifted the unit off the equipment stand! I guess you could call that air isolation; I called it a lightweight, and put a beanbag weight on it to keep it down. If the Benchmark components were judged by the old “weight principle”, the heavier the better performing, they would be deemed poor. That was a rule meant to be broken; don’t judge this component by its weight, or you miss a heavy hitter. The DAC3 DX does get warm to the touch when left on for long periods of time. In fact, when left running it was warmer than the AHB2 amps! I had no concern about excessive heat, however, as the unit was on a hard surface and not enclosed in a cabinet. I would not place the DAC3 DX into a cabinet and leave it running.

If you think that the mass of the chassis dramatically impacts the sound, then you will also be disappointed in the DAC3 DX. I don’t think high mass products would necessarily pass my law of efficacy. Typically, whatever is in the signal path directly is far more important to me, including cabling, than the chassis. The one exception I have encountered seems to be the TEO Audio Liquid Pre, which uses runs of its proprietary liquid conductor inside, reasonably argued to need extreme isolation from an overbuilt chassis.

A few comments on operations relates to the aesthetics and appearance of the DAC3 DX. It is helpful to the inquisitive audiophile to have both the word length (in bits) and sample rate (frequency in kHz) of a digital input signal indicated by the blue LEDs on the face of the unit. With use, only a glance at the indicators is necessary to ascertain their meaning. Similarly, the Power, DIM (reduces output by 20 dB) and Mute buttons reside next to each other, but on a horizontal plane to distinguish them from the digital information indicators. Perhaps a future version of the Benchmark DAC can incorporate a randomly generated pink LED which would appear anywhere on the indicators to keep things exciting, especially if it were not mentioned in the Owner’s Manual. I jest. Just checking to see if you, dear reader, are still awake.

The AHB2 Amplifier in appearance is rather like a prototypical Class A/B design shrunken to half-size. The faceplate exudes confidence and is relatively uncluttered for the amount of configurability the amp possesses. Rounded heat sink fins protect against snagging clothes or pricking fingers. Only from the back does the amp look busy. Manufacturers will never condone stacking amps, but the AHB2 runs cool enough that it would be tempting. It hardly feels warm to the touch, even after hours of use. I leave the DAC on because it is synced to the source, but the amps I turn off when not in use because I do not detect change in performance from warm up. Do not expect a solid-state amp with 0.0001% distortion to wander in terms of sonic character.

As to the remote control volume knob, it is not illuminated, I presume because one does not need an LED on a volume control at a studio console. Sitting 14 feet from the equipment rack I could just barely make out the red dot on the control when wearing my glasses. Perhaps Benchmark might consider a pinpoint light in future models. The volume control’s movement is smooth and graduated smartly, ramping up sensibly that regardless of the amplifier used I did not encounter “level explosions” from grossly, inappropriately set volume. However, less nimble-fingered users may find the speed of the control too quick for their comfort. An internal adjustment on the output might be in order (see below).

While I am discussing the volume control, “Hybrid Gain Control” is the name given to Benchmark’s combination of active analogue/passive low-impedance attenuation/32-bit digital gain structure with final servo-driven volume control. The clearly laid out, non-illuminated Remote features the controls found on the unit’s front panel. The Manual clarifies, “… digital inputs never pass through an analogue potentiometer. Digital inputs are precisely controlled in the 32 bit DSP system.” In this respect, the DAC3 DX rises to the level of an actively crossed speaker system, bridging the gap between a noisier preamp and a full-blown active speaker setup. In terms of listening, the preamp function of the DAC3 DX was exquisite, as commendable as the finest big buck preamps I have used. I concur with Benchmark’s assertion that the hybrid gain control preserves dynamic range.

Massive configurability is the name of the game 

The DAC3 DX and AHB2 Amps, in terms of their features, are inversely proportional to their scale. Again, I do not recall that I have seen more connections and switches jammed into such economical real estate. That does not account for the internal switches offering further adjustments! I’m not joking; as studio-worthy components these products are widely configurable.

As an example, the DAC3 DX offers internal gain jumpers to adjust the output of the headphone jacks, as well as Low Impedance Output Pads which (settings 0, 10 and 20) allow reducing the XLR output level to amplifiers and other downstream devices to maximize system signal to noise ratio. Without going into the unit one can also bypass the volume control, select USB 1.1 or 2.0, choose between system muting or non-system muting headphone jacks. Note: on the HGC and L versions, the D5 (digital coax) can be set for a digital output, allowing for digital pass through of the signal.

As regards the AHB2, it also has high configurability for an amp. It can be run in either Stereo or Mono mode (requiring 2 units), has three Sensitivity settings with the highest output in the uppermost position of the switch and the lowest output in the lowest position of the switch, and a choice between traditional output posts accepting speaker cables or NL4 SpeakON connectors (for both Stereo and Mono modes). The amp does not have RCA (single ended) inputs, and for that sin Benchmark has likely cut its sales of this amp. However, as someone who can shape shift systems between RCA and XLR interconnects, I much prefer the combination of options offered by Benchmark.

Regarding nomenclature on the AHB2, perhaps Benchmark would like to provide owners with a magnifying glass to read the labeling on the back of the amp. What do these people think, that everyone sits in a brightly lit studio that allows a walk behind connection of leads? Evidently so! I advise domestic users of a certain age, oh, say 50, to have both the Manual’s illustrations and a flashlight at hand when making connections. This is a product that justifies my overprotective protocol of triple checking connections.

Some of that little print on the back is very special, such as the phrase, “380W – 8 Ohm MONO.” That’s like finding an X on a treasure map! These little puppies pump out 380 Wpc into Mono! Recently I had a pair of $20K AVM Ovation SA 6.2 Monos in my room with three gain settings and they mustered only 335 Wpc into 4 Ohms. With favorable comparisons of features such as that, if you don’t have money to burn the AHB2 is an obvious choice.

Stringent words about cabling

Some audiophile companies promote the idea that their products are so well engineered that they are insensitive to audio cabling changes. Though Benchmark may not have stated it that clearly, it is certainly taken as such a company. Another one that comes to mind is Pass Laboratories. In reviewing three amplifiers associated with Nelson Pass, one of which being the First Watt J2 Amplifier, which by the way is my favorite of the three, I found all to be highly sensitive to power cable changes, despite each unit’s Owner’s Manual downplaying it. I shared this information with Nelson. However, an experience I had in ABX testing with amps shed lights on how Nelson and other designers might’ve arrived at their conclusion.

One of my more daring acts as a reviewer, and one which was truly fascinating to explore, was my review of the Audio by Van Alstine ABX Comparator, a device designed to allow the home audiophile to conduct randomly generated blind trials for level matched tests between components and cables. Whereas I was able to pass double blind trials in regards to comparisons of components and even cables, the only compared devices that I could not pass in double blind testing were amplifiers. In fact, I was not even able to surpass 50% accuracy in level matched blind trials between solid state and tubed amps! I hasten to add that was the case only under test conditions; apart from test conditions, in real world usage differences between amps are quite obvious. Later I discovered that my findings while using the ABX Comparator paralleled that of Frank Van Alstine. We had not discussed the results of my trials prior to the publication of the review.

Benchmark appeals to the characteristics of cabling used in studios, including the use of SpeakON connectors and Canare Star-Quad construction of the cables. This gives the impression that any cabling which meets specifications will be fine, and that the performance of the components will not be significantly enhanced by pursuing higher end aftermarket cables. I disagree and assert that the more finely tuned an audiophile component, the more it will benefit from aftermarket cabling. I have said in the past that if a component truly was insensitive to cabling changes it would be so compromised in terms of performance that it would not be worth owning. The best components are very sensitive to cable changes and influence systems dramatically when cables are swapped. We have here a slight difference of opinion between Benchmark and myself!

Complications made extensive testing more difficult than with products not designed with the studio in mind. The AHB2 amp accepts only XLR interconnects, and professional type connections are used on the Benchmark cables, versus the standard terminations employed in most domestic audio systems in North America. Thus, I was not able to compare “apples to apples” with perfect consistency. In this instance, I determined the best route to comparison was to assess the Benchmark loom in comparison to an aftermarket loom, a set of similar cables from Clarity Cable. The wires used from Clarity were the Vortex Power Cord, Organic XLR Interconnect, and Organic Speaker Cables. Clarity now has an upgraded line called the Supernatural and offers a USB and Speaker cable. I opted for the older Organic speaker cable in comparison because, like the Benchmark cables at the speaker end, it has banana terminations.

It got ugly before it got beautiful

The DAC3 DX proved to be powerfully influenced by the power cord used on it. I was not happy to discover that the USB input is tucked so close to the 15A IEC that none of the aftermarket power cords with round plugs would fit. Either the power cord would fit, or the USB, but not both. To my thinking, this is an egregious error in component design that moves the DAC3 into the category of components with idiosyncrasies to be considered prior to ownership. This is the assessment of someone who uses cables to adjust audio systems on a nearly weekly basis. Most studio techs would slap on the stock power cord and get to work. As a builder of fine systems for the home I work in a very different environment, and I’m not going to make such a mistake, yet Benchmark gave me few options.

Thankfully, I still had in my possession some older power cords, among them a Harmonic Technology Pro-AC 10, and it has a square plug on the IEC connector. That square housing eliminated just enough bulbous intrusion encroaching on the USB port that the USB cable could be slipped in alongside it. My displeasure subsided, and copious blessings were offered for Harmonic Technology. The improvement to the performance of the DAC3 DX was anything but subtle. If Benchmark would obtain such an improvement on performance by juggling the innards they could issue a new model designated the “DXL”. If you wish to hear this Benchmark DAC3 “D-excel” version at this time you must conduct due diligence with power cords.

This was not the only issue involving power cords, as I ran into a power cord problem with the diminutive design of the AHB2. The Benchmark Speaker Cable – NL2 to Banana – 2 Pole cables are designed to be the optimum tributary for the AHB2 amp. Remember the special SpeakON connectors and Canare wire? The AHB2 is designed so that the best performance is said to happen when the SpeakON connectors and Benchmark cables are used. However, when I attempted to use Clarity Cable Vortex Power Cords with the amps in Mono mode (the SpeakOn connector is tucked right underneath the power cord receptacle), the SpeakOn connector inhibited the insertion of the larger (fairly standard sized for an aftermarket PC) 15A IEC plug! I was beside myself with disgust! Not only were most aftermarket power cords prohibited for the DAC3 DX, but also for the AHB2!

The prohibitive layout of the back of these products when it comes to connections reduces their appeal for home high-end systems. Benchmark needs a “rethink” on this issue. It’s a good thing I’m actually testing, reviewing these products as opposed to “window shopping”, because I likely would cross them off my list for being so inhospitable to specialty cables. I would be very upset as a customer had I purchased these components, only to discover they are incompatible with aftermarket cabling. You will need to assess how important cabling is to you, and whether you can find workarounds for these limitations.

The same is true about theUSB cable; its input is scrunched next to the power cord on the DAC3 DX. I keep four or five USB cables on hand at all times, as it is among the easiest ways to tune a DAC, including the DAC3 DX. In moments I can address a shortcoming in sound quality by swapping a USB cable on the fly (Disclaimer: Do so at your own risk). The change in sound quality is comparable to that of changing a set of tubes in a tube amplifier. Do not fall victim to the misnomer that simply because Benchmark products measure superbly well there is no need to pursue extreme cabling. Benchmark products operate no differently than any other components from competing brands in that regard.

So, what about that comparison of cables between the Benchmark and Clarity sets? I set up the following components and rotated sets of cables between them: Salk Audio StreamPlayer III, DAC3 DX, AHB2 Amp (two in Mono mode), and PureAudioProject Trio15 PAP Horn 1 Speaker. I began with the Benchmark cables and played three selections, as it doesn’t take more than a few songs to determine whether there exists a difference in sets of cables. It does sometimes take much longer to determine whether those differences are significant enough to merit purchase, or are holistically more pleasurable with a wide variety of music.

Here are my notes with the associated pieces of music:

Candice Springs “Novacaine Heart” – Lots of warmth; piano strikes not sharp; treble fairly subdued; sounds “tubey”; nothing as sharply defined as I recall from mixed cable sets.

Lindsey Stirling “Electric Daisy Violin”: Violin does not “pop” out in performance; good bass presence and tautness.

The Piano Guys “Batman Evolution”: Good linearity, background clean; backing vocals cleanly heard; seems to be lacking some dynamic impact.

Here are my notes when I switched to the Clarity Cables set:

Candice Springs “Novacaine Heart”: Comparison over in 1 second, from first note; Candice’s voice more resonant; bass more expressive; can hear the venue; micro dynamics and definition superior.

Lindsey Stirling “Electric Daisy Violin”: Violin has necessary bite, especially with this music; bass/LF has more punch, weight; nuances in background clearer, more delineated.

The Piano Guys “Batman Evolution”: Orchestra more convincing; piano more palpable; less midrange emphasis.

The purpose of this comparison was not to render a final verdict of the Benchmark and SpeakON technology. That would take far more cable adjustments and listening sessions than I conducted. I suspect that a group of listeners who heard the comparison between the Benchmark and Clarity cables may have been split in terms of appreciation of the cabling sets. However, clearly the Benchmark cables did not sweep the results. It is not necessary to use the SpeakOn connectors or Canaire-based wiring for superb results. In fact, I believe one reason the Clarity Cables loom was more appealing overall was because elimination of the prohibited SpeakON connector under the power cord, allowing use of the Clarity Vortex Power Cords versus the stock power cord. It’s not so hard to get an excellent performance from a component, amp or otherwise, when good aftermarket power cords are employed. This is so, even though I didn’t season the sound to preference with mixing in, say, an alternate brand’s power cord, XLR interconnect, or speaker cables. Slight derivations from entire looms of one make can provide even more appealing sound.

I suspect Benchmark is less than gleeful about this assessment of the cables, as I write to inform the audiophile of the expected performance of the manufacturer’s products. Reasonably, the DAC3 DX and AHB2 are designed to have superb measurements, and the cables are designed to work well enough. I concur; you can get very good sound with them. While the Benchmark cabling is inexpensive enough to start your audio system, do not feel constrained as though better sound through alternative cabling is unattainable. It took only one set of alternative, and yes, much more costly, power cords and speaker cables used in conjunction with the AHB2’s more traditional output posts to revise the performance. You may be content with the synergy of the all Benchmark system, but stay open to the thought that the components can perform beyond your expectations with upgrades in cabling.

I hope that it does not seem as though this review is turning into a flame of the Benchmark components. It isn’t, as I am now finished with fault-finding. My objections are confined largely to the foibles of the ergonomics, and the limitations of the cables and connections, not the performance holistically. As with other components I can more easily accept such things if the performance overall is noteworthy. Thankfully, with the DAC3 DX and AHB2, that is the case. That’s enough of the “ugly truth” according to Doug Schroeder. Let’s move on to the beautiful truth.