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Benchmark DAC2 HGC impressions (and Linux setup notes)

My new Benchmark DAC2 HGC arrived on Friday. I liked the idea of a compact device which could serve as DAC, preamp and headphone amp, offering state of the art performance all around.




Tidy interior layout with switch mode power supply (SMPS). Note the attention to detail with shielding and grounding: Unpainted areas around the (non-anodized aluminum) case screw holes ensure good conductivity between the case halves. Note also the gold-plated pads where PC board is affixed to the case and ferrite beads on all RCA jacks: DAC2 meets the more-stringent FCC Class B standard for radio frequency emissions.

After leaving it powered up through the better part of a very warm evening, I measured the temperature of the case at 38ºC / 100ºF: Warm to the touch, but not uncomfortably so. Pressing the power button once puts it into Standby mode, but that seems to do nothing but switch off the front-panel LEDs, and has little effect on case temperature. Press the power button a second time, and it powers down, with an audible "thump" through the RCA outputs, so best to switch off your power amp first, and reverse the order when powering up.




I unplugged the Objective DAC from my Linux Mint 14 music PC, and plugged in DAC 2 in it's place via USB. Selected it as my audio output device, then proceeded to listen to...silence. I tried a number of current Linux distros: Linux Mint 15 (Cinnamon), Linux Mint 15 (Mate) Fedora & Ubuntu. In some cases, I'd get functioning sound out of the DAC immediately after a fresh OS install, only to lose it after running system updates. After much flailing-about, I figured that:

DAC2's USB 1.0 mode doesn't work with Linux kernel 3.8.x, but USB 2.0 does. So switch it to USB 2.0 and forget about it. Next, I figured that the audio was simply being muted in some instances. The solution is to open a terminal window, run AlsaMixer, hit F6 to configure the DAC 2. Even though their levels cannot be altered (they're fixed at 00), the first two items must be unmuted in order to get any sound:



And on those occasions where there was still no sound coming out of the DAC2, I powered down both computer and DAC for a couple of minutes and tried again. That seemed to work.

I also briefly tried it via USB 2.0 hookup to my iMac running OS X Mountain Lion as well as a late-model Thinkpad running Windows 8, and it worked without a hitch, though USB 2.0 audio under Windows requires additional drivers which I downloaded at no charge from Benchmark's web site.

I haven't bothered attempting to bench-test DAC2, because whatever it's distortions, they're likely to be far below the resolving power any remotely affordable test instruments.

So how does it sound? I expected it to sound pretty much the same as my Objective DAC + O2 headphone amplifier, which I had been using as a preamp, directly driving my powered speakers. And that's mostly true in this situation: No sonic signature that I can discern, and not a hint of added hiss or hum.

About noise: Before I got the O2+ODAC combo, I thought that a small amount of hiss and hum was nothing to worry about, as it'd be quickly overwhelmed by the music, and in any event, no listening room or concert space is totally silent. But it turns out I was wrong about that: Even if it's just a split-second of room noise or inhaled breath before the first note is played, there's a wonderful sense of hearing even the faintest details in a recording as never before, now that it's no longer masked by the noise floor of the playback system.

As a headphone amp, I expected to hear no real difference versus O2, but in fact, I think I hear a bit of added crispness and clarity with DAC2. But that isn't necessarily a good thing with sibilant recordings! Maybe I'm overdue to upgrade my Grado SR60s to something (a lot) better. Meanwhile, I think a cheap tweak might sweeten the sonics just a smidgen and let me get away with using the SR60s for awhile longer: A 0.5 ohm resistor placed in series with the headphones to lower the DAC2's damping factor a smidgen. Maybe the SR60s just don't sound the best when controlled with such an unyielding vise grip as the DAC2? The series resistor brings it more in line with the output impedance of O2 (0.54 ohms versus "<0.11"). Yes, a fidelity-robbing kludge, but just a small one costing a few pennies.


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Topic - Benchmark DAC2 HGC impressions (and Linux setup notes) - 4season 21:59:17 06/30/13 (2)

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