None of us wants to spend more than we have to in order to enjoy great sound, which begs the question: are portable headphone amplifiers really necessary? To answer this question, it is important to bear in mind that there is a big difference between driving high-performance earphones (as in “get them to make sounds at reasonably satisfying volume levels) vs. driving them well (as in “extracting the fullest measures of power, resolution, delicacy, and finesse of which your earphones or monitors are capable”).
Without knocking iPods (or there brethren) in any way, it is fair to point out that A) their analog audio circuitry is good but not great, and B) they do not offer the most powerful/capable amplifiers around. Therefore, the key to superior sound—at least for listeners with high-end tastes—is to A) find ways to bypass as much of the iPod’s analog audio electronics as possible, and B) to connect the iPod to amps that offer more power with less distortion. This, in a nutshell, is precisely what ALO Audio’s solution allows.
In the preceding paragraph, I mentioned that one of the keys to getting better sound quality from a portable, iPod-based system is to “bypass as much of the iPod’s analog audio electronics as possible.” To do this, you’ll need what many high-end portable audio enthusiasts call an “LOD” or “Line Out Dock” cable. Basically, an LOD cable pulls line-level analog audio signals from downstream of your iPod’s onboard DACs, almost completely bypassing the actual amplifier section of the iPod. When you use an LOD cable, for example, you’ll discover the iPod’s volume control has no effect on the outbound signal; that’s because the signal is bypassing the iPod amp, including the amp’s normal volume controls, etc. Then, the LOD cable routes this relatively clean, pure, unadulterated analog audio signal into your outboard portable amp, which in turn offers much, much higher performance than the iPod’s own amp section could ever hope to provide.
Note: As a general rule, LOD cables are configured with a multi-pin Apple-time connector on one end and a 3.5mm mini-plug on the other. Some manufacturers, ALO Audio among them, do build LOD cables for non-Apple devices, though for obvious reasons LOD cable for Apple products are much more commonly seen.
ALO Audio makes several different grades of LOD cables, and Ken Ball graciously loaned Playback a sample of his finest model—which is called (no, I am not making this up) the ALO Audio 18awg OCC Triple Pipe Cryo iPod/iPhone Cable ($195). Translation: this very special cable uses conductors made of 99.99998% pure Ohno Continuous Cast (OCC) copper wires, which have been cryogenically treated. The cable features three bunches (hence the name “Triple Pipe”) of 144 strands of finely drawn wire, each encased in a polyethylene (PE) jacket. The wires are connected, says ALO, to a modified “premium Switchcraft Gold mini plug,” through which the iPod makes connection with the ALO Audio Rx Mk2 amp.
Does this pricey little cable really make an important difference? You’d better believe it does—enough so that, once your hear that sonic difference through a really good set of earphones, you might never be willing to go back to listening the old way. Also note that, if the $195 price of this mega-cable is a little too rich for your blood, ALO offers many alternative LOD cables—some starting at about $55.
Most portable headphone amplifiers improve upon the sound of the iPod’s own amplifier in some ways, but what sets the ALO Audio Rx Mk2 apart is that it improves upon what the iPod can do in virtually every way imaginable—often by quite dramatic margins. Let me provide some details to explain my point.
iPods can, when heard through high-quality earphones, have a somewhat brash, ragged or raw quality that can make music—especially music that hinges on sonic delicacy and finesse—sound clumsy, overwrought, or a bit “out of control.” With the ALO Audio Rx Mk2 in play, however, those problems largely go away. This amp sounds consistently smooth, yet at the same time very clear and detailed, which is one of those high-end audio feats that easier to talk about than it is to pull off in reality. To hear what I mean, here, try listening to “The Last Fallen Leaf” from the late Chris Jones' album Roadhouses & Automobiles [Stockfisch]. The track features a beautifully recorded solo acoustic guitar performance that is richly detailed. Through an iPod, tiny performance details, such a finger squeaks, fretting noises, or high-pitched overtones, take on a glassy, exaggerated, “zingy” quality that, while initially exciting and dramatic, sounds more and more unnatural and just plain wrong as you listen further.