Input connections are either analog using a 3.5mm mini jack cable, or digital using the supplied USB cable. For portable use, the amp comes with a stretchy pouch that includes a pocket to hold your iPod or other personal music player. This makes for a tidy if somewhat hefty bundle that you can stick in your pocket, although you’ll need to pull your player out if you want to change tracks or make other adjustments. Fortunately, the headphone jack and volume control are both at the same end of the amp, so it’s easy to make volume adjustments without having to pull the amp out.
Making the USB connection to my Windows laptop was no problem; it simply connected automatically and switched over from the laptop speakers when I plugged the cable in. I was able to play files using several audio players including iTunes, but for most listening I used Winamp, adjusting the maximum output resolution to match the amp’s 96kHz/24-bit capability.
In use I found the amp had a few quirks including an audible pop when I turned on the power, and a noticeable level of background hiss. This was especially audible when I was using my Ultimate Ears UE-10 Pro in-ear monitors, sounding quite similar to analog tape hiss. The volume control also produced a low level rustle as you adjusted the level at times, although this would remedy itself if you worked the volume dial back and forth a couple of times.
Despite its compact size, the ADL proved to be quite capable of driving most of the headphones I had on hand. Tougher loads like the HiFiMan HE5s were no sweat, and I found I could crank it up pretty loud and still have plenty of punch and control. More likely partners for on-the-go use that I tried included the previously mentioned Ultimate Ears, B&W P5s, Monster Turbine Pros, Thinksound ts02s, and Etymotic hf5s.
The first test of any portable headphone amp is whether it can outperform whatever personal music player you’re using with it; otherwise, what’s the point? Happily this isn’t a problem for the ADL, which easily outstripped both my iPod Classic and my iPhone 4 in its ability to drive headphones with plenty of dynamic nuance and drive, while opening up a clear window onto the recording.
Tonally the ADL is quite neutral, yet it has an uncanny ability to exploit the strengths of most headphones without highlighting their weaknesses. For example, it did a great job of pumping a little extra life into the super smooth yet somewhat laid back B&W P5s, pulling more detail and transparency from the upper midrange than I’m used to hearing from that model. On the other hand, the Etymotic hf5s balance typically puts a spotlight on the midrange, yet the ADL managed to really flesh them out in the lower octaves, getting a detailed grip on the bass energy in the recording.
One upshot of the ADL’s upper midrange clarity is the impressive spaciousness and finely focused detail of the soundstage. On good acoustic recordings it was easy to identify the space occupied by each instrument, separating out the layers of a recording with plenty of breathing room for each performer. Soundstage width was good, but it was the sense of depth on suitable recordings that really had me impressed.
With so much dynamic life coupled with its exceptional transparency, the ADL really manages to hold its own even against some dedicated home amps. Still, a comparison with the $800 Musical Fidelity M1HPA showed how the bigger amp’s pure class A circuitry gives it a slight edge in subtler micro-dynamic shadings. The M-F amp also presents the music against a blacker, quieter background, making it a bit easier to pick out the tiniest nuances.
While most of my listening was performed using the ADL’s analog input, the built in DAC is certainly no afterthought. Comparing WAV rips from the same CDs using the iPod into the analog input against the laptop through the USB, showed a small but clear preference for the digital connection. Tonal contrasts were more vivid over the USB, giving the music a richer overall sound.
You may have noticed that I have generally referred to the Cruise and Stride collectively as the ADL amp. To see if I could detect any differences between the two amps, I did perform some careful comparison tests. First, I adjusted the volume controls on each amp to the exact same level using a test tone while measuring the voltage at the headphone socket. Then I played several tracks, alternating back and forth between the Cruise and the Stride. While at times I thought I had a slight preference for one over the other, these impressions were not reliable, and on the following trial any slight preference would often swing the other way. This isn’t a subtle way of saying that my hearing is going off, just that any possible differences were so tiny that they became irrelevant. I think that the question of whether the Cruise is worth the additional cost really depends on how much you value its slick cosmetics.