HeadRoom Micro Amp + Micro DAC
In my coverage of under-$100 headphones for Macworld, I’ve been consistently impressed by the sound quality today’s models are capable of when paired with an iPod, iPhone, iPad, or Mac. But there’s a whole ‘nother world out there—one where vendors aren’t forced to cut corners in terms of components, design, and manufacturing in order to hit a “consumer” price point. Enter this world, and you’ll be greeted with headphones designed to wring every last bit of accurate musicality out of your media, no matter the cost—price tags of $300, $600, $1000, or more are common.
But you can’t just plug these high-end headphones into the headphone jack on your Mac or iOS device and expect spectacular sound. Most built-in headphone jacks are afterthoughts that don’t do good headphones justice, and, for sources such as computers and digital-media players, the built-in digital-to-analog converter (DAC) leaves a lot to be desired. For the best possible sound from great headphones, you’ll want to bypass your device’s built-in audio circuitry with an external DAC and a dedicated headphone amplifier.
HeadRoom is an online headphone-gear retailer that also makes amplifiers and DACs for getting the most out of your headphones. The company sent Macworld its $349 Micro Amp and $299 Micro DAC, which together are also known as the $649 Micro Amp + DAC Package. Though each is near the bottom of the company’s hardware line, which extends into the four-digit range, the resulting combination isn’t inexpensive, and it takes the performance of the higher-end headphones I tested to impressive levels.
A built-in problem
First, some background info: Most listeners plug headphones into the built-in headphone jack of the device they’re using. But on most devices—even some pricey home-stereo components—the quality of audio from these jacks is limited by cost, space, and power. But headphones are basically miniature loudspeakers, and they require power to make those speakers move and, thus, to move air. This is particularly true for headphones with large drivers or for inefficient headphones. (Put generally, inefficient speakers require more power to produce the same sound level as more-efficient models.) An external headphone amplifier can provide more, and higher quality, power than the typical stock headphone jack, ensuring precise control of headphone drivers and the capability to reproduce the large dynamic swings and powerful bass that make music dramatic. Indeed, many higher-end headphones are designed with a dedicated headphone amplifier in mind.
Similarly, all digital-media players with analog audio outputs contain a built-in digital-to-analog converter, which takes the stored digital representation of music and converts it to an analog signal (which is then fed to the headphone jack or other output circuitry). Internal DACs—especially those in consumer electronics such as iPhones, iPads, TVs, and computers—tend to be made from inexpensive components. In addition, a built-in DAC’s physical environment—crammed into a tiny space next to a bunch of other electrical components—subjects the analog audio signal to electrical noise and interference from other circuitry. An external DAC pulls the digital signal outside this environment before converting it to analog, and typically uses considerably higher-quality components to do so, giving you a cleaner, more-accurate reproduction of the original recording.
The Micro Amp and Micro DAC each sports a roughly rectangular, black-anodized-aluminum enclosure with dimensions somewhere between those of an iPod Classic and a paperback book. These enclosures are gently curved on the top and the bottom to allow the two units to stack. (Indeed, HeadRoom sometimes calls the two units, stacked together, the Micro Stack.) Although some headphone amplifiers look like objets d’art, the stack looks unassuming, but, in my opinion, charming. If you want to purchase both units, HeadRoom offers a $649 bundle that includes a few cables otherwise sold separately.
The back of the Micro DAC features a power connection (which connects to a power supply that’s approximately the same size as the Micro DAC itself); a 1/8-inch, analog-audio-output jack; and three digital-audio inputs: Mini-USB, Toslink optical, and 1/8-inch coaxial. The USB input accepts up to 16-bit, 48 KHz audio and will work with a Mac, Windows PC, or—via Apple’s iPad Camera Connection Kit ( )—the iPad. The optical and coaxial inputs accept high-resolution audio files up to 24-bit, 96 KHz. The Micro DAC’s front side has two simple switches: one to turn the unit on and off, the other to switch between the three inputs.
The Micro Amp’s rear panel features the same power connection; two 1/8-inch, line-level audio inputs; and a volume-knob-controlled 1/8-inch audio output. (The last output allows the Micro Amp to perform double duty as a stereo preamplifier.) The front features a power switch, a sturdy volume control, a gain selector switch (to better match the volume control’s sensitivity to the efficiency of connected headphones), an input-selection switch, and a 1/8-inch headphone jack. (Why not a 1/4-inch jack, given that many high-end headphones have a 1/4-inch plug? A HeadRoom representative told me that a 1/4-inch plug was too large to fit inside the Micro’s chassis.)
The Micro Amp also features one other front switch, labeled Crossfeed, which enables or disables Headroom’s proprietary headphone-imaging circuitry. This circuitry adds a small amount of the right channel audio to the left channel, and vice versa—an effect called, appropriately enough, crossfeed—with the claimed effect of more-natural sound and improved stereo imaging.
Does it really make a difference?
For most of my time evaluating the Micro combo, I used iTunes to send CD-quality music—meaning tracks encoded at full CD quality—in Apple Lossless format to an Apple AirPort Express ([[4 mice]]), with the Express’s optical-digital output connected to the Micro DAC’s optical input. Given that the Airport Express is limited to 16-bit, 44.1 kHz audio, I also did some listening with the Micro DAC connected directly to the optical output of my Mac in order to test the DAC’s decoding of high-resolution audio (and to ensure that the Airport Express wasn’t degrading the system’s performance). Similarly, I also connected my Mac directly to the Micro DAC’s USB input to test that functionality. The Micro DAC was connected to the Micro Amp via HeadRoom’s $10 Mini-to-Mini Cable, which isn’t included with either component but the company included with our review system. (If you purchase the $649 Micro Amp + Micro DAC Package, HeadRoom includes the $18 Cardas 6-inch Mini-to-Mini cable.)
As for headphones, I focused on Audeze’s $945 LCD-2 Planar Magnetic Headphone, loaned to us by Audeze, which is spectacularly good and among the current state of the art in headphone performance, as well as AKG’s excellent $499 K 701, which many audiophiles still consider to be among the best on the market. For testing purposes, HeadRoom also loaned me the $650 Sennheiser HD 650, and the $349 Denon AH-D2000, each roughly comparable to the AKG K 701 in terms of performance, although differing in sonic character. In the process of getting to know the system, I also used it with a number of in-ear models I’ve reviewed.
Using the Audeze LCD-2, the Micro combo offered immediately noticeable improvements compared to my MacBook’s built-in headphone jack. Instrumental textures were improved across the entire frequency spectrum. Drum-kit sounds, especially snares and cymbals, were clearer and more detailed, and they gave the music a better sense of momentum. The midrange—vocals in particular, but also guitars and keyboards—sounded richer, more substantial, and more realistic. Bass was tighter and better controlled, with more body and depth due to improved extension at the lowest frequencies. There also seemed to be more audible separation: I heard more silence between successive notes, individual instruments were more distinct, and each sound seemed to occupy a more precise place in the space between the two earpieces. Most of these improvements seemed relatively small compared to, say, the differences between headphones, but they added up, and I found myself enjoying music much more when the headphones were plugged into the Micro combo.
Although the LCD-2 is very good, different headphones respond differently to changes in amplification, so I also tested the Micro combo using the AKG K 701 and Sennheiser HD 650. The effect of the Micro combo was more dramatic with the AKG K 701, which is notorious for “needing” good amplification to sound its best. When connected directly to my computer’s headphone jack, the K 701’s high frequencies sounded harsh and indistinct, and bass sounded flabby with decreased extension—in other words, the K 701’s best qualities were less pronounced, while its worst qualities remained. When I switched to the Micro combo, treble was immediately clearer and more distinct and bass was much tighter, extended deeper, and was more balanced with the rest of the frequency spectrum. As for the Sennheiser HD 650, when driven by my Mac’s headphone jack, it initially sounded pretty good. But switching to the Micro combo provided improved detail across all frequencies, as well as an increase in bass extension and authority. But even more noticeable was that music had more drive and a more-compelling apparent tempo, suggesting that the Micro combo significantly improved the HD 650’s resolution of musical transients.
As mentioned, I also tested several different digital-connection configurations with the Micro DAC. I did not notice any difference in performance when the Micro DAC was connected to my Mac’s optical output compared to the Airport Express’ optical output (Tests have demonstrated the veracity of the digital output of the Airport Express.) I also confirmed that, when connected directly to my Mac, the Micro DAC decoded high-resolution audio, although I’m not sure I noticed a difference in quality compared to standard CD-resolution audio—my test recordings could be to blame. Interestingly, when connecting my Mac to the Micro combo, I did hear slightly more detail over an optical connection compared to the USB connection. (I didn’t test the Micro DAC’s coaxial input because I didn’t have the necessary RCA-to-mini cable.) If your source(s) offer more than one digital output, I recommend testing each type of connection to see which sounds better to your ears.
Normally, any sound you hear will reach both of your ears (though not necessarily at the exact same time and at the same volume). However, when listening to recorded audio through headphones, any sound contained only in the left channel or only in the right channel never reaches the other ear—you’re subjected to the unnatural phenomenon of hearing a sound in only one ear, which often leads to listening fatigue. (I personally find that it produces a “ticklish” sensation in the ear.) To attempt to counteract this effect, HeadRoom’s amps include special circuitry that implements what is commonly called crossfeed. As noted above, crossfeed circuitry sends—with a slight delay and at a slightly lower volume, to account for the distance between the ears—some of the left-channel audio to the right ear and some of the right-channel audio to the left ear. With crossfeed engaged, the typical “hard-right/hard-left” effect is eliminated, or at least greatly reduced, albeit at the cost of a slightly narrower stereo image.
If found that HeadRoom’s crossfeed circuitry did indeed make listening more comfortable, and I didn’t notice any degradation in audio quality, so I listened to the Micro Amp almost exclusively with the feature enabled. If you’ve avoided serious headphone listening because of fatigue from extreme left/right-channel separation, you’ll find the Micro Amp particularly appealing.
Comparisons with similar gear
I’m not a stranger to HeadRoom’s products—for the past four years, I’ve done most of my home headphone listening through the company’s $149 HeadRoom Total BitHead, a “budget” combination of an amplifier and a DAC. The BitHead is a little under half the size of the Micro combo, offers only one digital (Mini USB) and one analog (1/8-inch) input, and is powered by either USB or battery power. Comparing the Micro combo to the Total BitHead, I heard many of the same differences I observed when comparing the Micro combo and my MacBook’s own headphone jack, but the Total BitHead’s improvements were less dramatic. Still, the Total BitHead offers a good portion of the Micro’s benefits at a much lower price. The Micro combo’s most noticeable advantages were in bass performance and in background noise—when listening with very efficient headphones such as canalphones, the Micro combo has significantly lower background noise than the Total BitHead.
HeadRoom Micro Amp + Micro DAC