DACs

Benchmark DAC2 HGC

ARTICLE INDEX

Introduction to the Benchmark DAC2 HGC

I think it's fair to refer to the Benchmark DAC2 HGC as a DAC since that is its official title, or a headphone amplifier but the owner's manual refers to it as a 'Reference Stereo Preamplifier'. Whatever you call it, this little box does a lot. I reviewed it mostly as a DAC but tried out the preamp and headphone functions as well.

BENCHMARK DAC2 HGC SPECIFICATIONS

  • Design: Stereo DAC, Preamp and Headphone Amplifier
  • Connections: Inputs (analog): 2 x Stereo Unbalanced, Inputs (digital): 2 x Toslink Optical, 2 x Coaxial, 1 x USB
  • Outputs: 2 x RCA (unbalanced), 1 x XLR (balanced)
  • 1 bi-directional 12 volt trigger
  • Dimensions: 1.7" H x 9.5" W x 9.3" D
  • Weight: 3 Pounds
  • Price $1,995 USD
  • Benchmark
  • SECRETS TAGS: DAC, Preamplifier, Headphone Amplifier

 


Design and Set up of the Benchmark DAC2 HGC

It has a plethora of both digital and analog inputs as well as one balanced and two unbalanced outputs that can be programmed to be amplified or line level. The 'HGC' in the name stands for 'Hybrid Gain Control' and refers to the different types of gain employed depending on the type of input signal. The types of gain are active analog (this is the standard sort of gain for a preamp), passive low-impedance attenuators, and a 32-bit digital gain control. The analog control is used for analog sources, digital for digital, while the passive attenuation refers to the ability to adjust the output level on the balanced (XLR) outputs. The manual talks about the importance of using this feature to match the DAC2 to your particular amplifier when the DAC2 is being employed as a preamp. But in discussions with Benchmark's Chief Engineer, John Siau, it came out that the adjustment is recommended even if you are connecting the DAC2 to another preamp. In that case you would try the different settings on the internal jumpers - 0, -10 or -20db (-10 is the default setting), selecting the one that gives the system the loudest volume setting you think will employ with the external preamp's volume control set to near its max. If you are not using an external preamp the process is similar but calibrated to the DAC2's own volume control.

That front panel volume control is used for both the digital and analog volume control. In the case of analog it's a servo-driven gain circuit control built around a custom-made Alps potentiometer. That in itself is already music to an audiophile's ears. The digital volume control is used for digital sources and while this might sound like 'not-music' to an audiophile's ears we should note that digital volume control has come a long way. While it's true that it still means a loss of resolution as compared to analog volume control, new techniques mean that the amount lost is 'down in the noise' and has to be compared against the noise in the analog option. Basically, the method is to pad (fill out) the 32 bit data word with 0's and use mathematics – i.e., multiplication, to adjust the volume rather than simply throwing away bits from the original word. If you're into such things it's explained for real in this paper by ESS:

http://www.esstech.com/PDF/digital-vs-analog-volume-control.pdf

Benchmark isn't the first or only company using this technique of course, but to my knowledge they are the only company building headroom into their digital processing. If you understood all of the above about digital vs. analog volume control then you know that a premise of digitally sampled music is that the loudest possible signal uses all of the available bits and there is no more, if the actual volume of the input signal is higher than the digital system has been calibrated for, you have noise of the worst kind. Commercially released CD's should not have this issue (though some probably do). Benchmark has discovered though that even if a CD is recorded properly, the interpolation process used as part of the processing can still produce 'samples' that are above what was meant to be the 0db level. By 'leaving some room' – headroom that is, in the digital processing chain the DAC2 avoids the artifacts that come from processing these samples.

There are a multitude of internal adjustments possible with the DAC2, in addition to the aforementioned output level, the gain of the headphone amp can be adjusted and the muting behavior of the outputs when headphones are plugged in. I stayed with the default setting in all cases.

Like the DAC1, the DAC2 has a utilitarian front panel array of LED's to indicate which input is active and the bit rate detected on the input. The remote is a delight, slim yet substantial all-metal construction.

Since I received my review sample of the DAC2 Benchmark has come out with two reduced-feature models. Both have the same internals and performance as the HGC but remove an item or two to get the cost down (a little). The DAC2 L is all the same as the DAC2 HGC but without the headphone amplifier. The DAC2 D keeps the headphone amp but loses the analog inputs and the 12V trigger. Each of these new issues is $1795 or two hundred less than the HGC.

Also in the design realm I think – the user's manual. Benchmark is in the habit of putting out some of the best manuals in the business. Besides exceedingly clear instructions (with one notable exception in this case), they contain a nice smattering of design theory explaining what you've paid for – engineering expertise. The exception in this case is an incomplete instruction in regards to the driver installation. The manual says: "run the setup.exe from the zip file. Do not decompress the zip file and run the setup.exe". I'm not sure how you run anything without decompressing the zip but the difference seems to be in whether you unzip to some location on your computer other than where the zip file landed when it was downloaded.

 


The Benchmark DAC2 HGC In Use

While I'm going on about the driver, getting the DAC2 to work with my computer was not as straightforward as I (or probably you) have become accustomed to with USB devices. Making a very long story short it seemed to boil down to the fact that I had previously installed CEntrance's version of ASIO drivers on the two computers that I had trouble with (one Windows XP the other Windows 7). Removing those and installing the Benchmark driver (also ASIO) seemed to clear it up. Likely you won't have this issue. On yet another Windows 7 computer that I had access to, the Benchmark was indeed plug and play for USB 1.1 (good up to 96 kHz, 24 bit data word). Installing Benchmark's driver gets you higher resolution (up to 192 kHz) as well as DoP (DSD over PCM). I did take some steps towards playing some DoP files but since I could not find a free player that didn't require multiple steps and downloads to get working and since the only recordings available are obscure Audiophluffery I gave it up. I'll try again when Joy Division is available in this format.

A note on power cords:

I found the Benchmark to have a much lower noise floor and 'ease' about its job when powered by a Shunyata Venom-HC. This power cord is quite heavy and is intended for high current components but the DAC2 was clearly better with this than with a Venom-3 or the stock cord. The DAC2 does get mildly warm when powered up so maybe it is drawing some current after all. 'Mildly warm' is a most welcome improvement over the DAC1 which runs on the hot side.

As a DAC:

I compared the DAC2 to both my Naim DAC (with XPS) which I still have around and my new favorite digital player, the Parasound CD 1. In all cases I used the Parasound as the source. Like the CD 1, the DAC2 was better at pulling instruments apart and into their own space than the Naim. The Naim does have its famous warmth, especially with voices, but that seemed to be as much blurring as warmth when compared to either the Parasound or the Benchmark. Both the Benchmark and Parasound extended bass to a greater degree than the Naim as well.

Comparing the Benchmark directly to the Parasound, I found that the latter could delineate the room presence to a greater degree while the Benchmark did a better job with timbre, the texture of the instruments. Thus I found that I preferred the Benchmark for electronic music where the techy quality of carefully crafted synth sounds is key. Listening to Lida Husik's Faith in Space was once again a transporting experience. For more raucous music like Holly Golightly's latest effort with the Brokeoff's I preferred the Parasound.

I should say that the differences were minor and I could easily live with either one of these as my digital converter. I switched back and forth several times (this required swapping cables as my Sim preamp has only one balanced input) and each time I felt like I was going to miss the one being disconnected.

As a headphone amp:

I sampled the DAC2 with both Grado 325i's and Focal Spirit One cans. The DAC2 was more than capable of driving either of these and made them each sound their best. The Focal's are great for travel with their closed-back design offering a reasonable level of sound isolation without noise cancellation but they sound like a closed-back design, there is a bit of constriction and what seems like a struggle to get the sound out. The DAC2 pushed through this quite well and got me into the music. With the Grado's there is no pushing required, this open-back design is fast and delicate but also able to produce deep bass when driven correctly and the DAC2 was all over it. I couldn't get enough of my Grado's through the DAC2. When I was finally forced to unplug I noticed that the 1/4" headphone jack was on the warm side. Yes the DAC2 generates a little heat.

As a preamp:

Replacing my Sim P5.3 with the DAC2 I found that I probably needed to adjust the passive attenuation of the output pads to the next lower level as volume was too loud with CD source even with the control near the low end. Furthermore, turning the knob down just a little from there turned the volume down a lot. No satisfaction. Still listenable though at the high level so I didn't crack open the box. How did it compare then? I wouldn't necessarily say 'more transparent' or something like that. Rather, it was that different things were emphasized. Bass especially seemed if not more pronounced, better delineated. For instance, track two of the aforementioned Holly Golightly and the Brokeoff's 'Sunday Run Me Over' is called, "They Say". This track features a didgeridoo (or something that sounds like one) in the background, seemed much more in the foreground when using the DAC 2 as the preamp.

All of that was using the DAC2's DAC function of course, I wanted to try it as a straight preamp for playing vinyl but since the DAC2 has only unbalanced analog inputs (there's just no room for another XLR pair) I had to switch to my trusty old AudioQuest Sidewinders instead of my pricey Nordost Blue Heaven balanced wires. So, this comparison was certainly colored by that change. But once again I found that bass was more pronounced, very pleasantly so I would add, though I didn't listen long. Listening to the first side of the (45 RPM) Atoms for Peace first and only record, 'Amok', seemed like a slightly different mix. This is how it goes with hifi – sometimes things are different and it's not clear which, if any, are correct. The point is, it sounded great! The higher frequencies, way up there, like hand-claps and symbols, were not quite as crystalline through the Benchmark as compared to the Sim but it was a small difference and not enough to sway me from potentially using the DAC2 as a preamp. If time had allowed it certainly would have been an interesting experiment to dial-in the Benchmark (using the passive output attenuator adjustment) and redo this comparison. Any pre-amp/amp combination is something to try-before-you-buy. To me, the fact that Benchmark is taking the extra step to add this adjustment shows their dedication to the task.

 


The Benchmark DAC2 HGC On the Bench

I'm sorry to report that we couldn't get the DAC2 talking to the Audio Precision test system used for Secret's audio measurements (at Chris Heinonen's house). The issue seemed to be not so much to do with the DAC2 but with Windows 8 and the driver for the Lynx sound card used in that system. We didn't have time to track it down further so that's all I can report.

 


Conclusions about the Benchmark DAC2 HGC

The Benchmark DAC2 HGC does so many things – I didn't even get to all of them – and does them so well, it's easy to recommend. Got an old amp and you need a preamp to make a system out of it? DAC2. Want a first class headphone amp? DAC2. Computer audio? Of course. It's not the least expensive option for any one of those but it might well be the most affordable when you compare to other solutions that are as versatile – if you can find any. The sound is sweet, engaging, and long on textural detail without fatigue. You should definitely check this DAC out.