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  Boostaroo Revolution Portable Headphone Amplifier

      Date posted: November 5, 2007

Boostaroo RevolutionSuggested Retail Price: US $49.99
www.boostaroo.com

Of the myriad accessories now available for portable music players, and specifically iPods, only a tiny fraction have anything to do with improving sound quality. If you want to hear more from your portable it pretty much comes down to headphones and headphone amplifiers. Designed to drive the cheesy white earbuds that come with the thing, the headphone amplifier in an iPod isn’t quite up to the task of driving the more difficult loads presented by less sensitive, larger, sealed or open-back type cans like the big Sennheisers and AKGs. There are any number of audiophile endorsed headphone amps which can solve this problem, of course, but few, alas, are even remotely portable, not to mention as affordable as this one.

The Boostaroo Revolution aims to fill this void with an inexpensive, battery-powered headphone amp you can strap directly to your iPod. When mated to an iPod, however (something they suggest you do with a Velcro kit you procure yourself – none is included), especially to the Mini or the Nano, the ergonomics are less than ideal; the long and square Boostaroo being of a rather incompatible shape to the wide and thin iPod. Oh well, the mandate here is more about sound quality with big headphones than about portability, and besides, who goes jogging with big, open-backed cans on anyway?

If carrying the thing around is something of a hassle, at least operation is simple as could be. Plug the output from your player into 1/8” mini jack on the top of the Boostaroo and your headphones into one of the two 1/8” mini jacks on its side and you’re pretty much ready to go. The two output jacks will let you share with a friend too, with, claims Boostaroo, no loss in fidelity or power (but, one would assume, a drop in battery life).

The device turns on automatically and the indicator light comes on when a cable is connected to its input. Unfortunately only a 12” mini to mini cable is provided, which only further exacerbates the ergonomic problems of the Boostaroo’s shape. Assuming you’ve rigged up some Velcro or an elastic to bind iPod and Boostaroo together, a cable of only a few centimeters would be ideal. Twelve inches of cable, in addition to your existing headphone cable, is just a tangle waiting to happen, so pick up a shorter one when you’re out buying Velcro and rubber bands. Oh, and don’t forget to pickup some AAAA batteries while you’re at it. Yes, that’s four A’s, smaller than AAA’s, and not that easy to find so get a bunch. Fortunately the batteries are supposed to last for around 20 hours. Just don’t leave the cable connected to the input and drain the batteries when you’re not using it.

So just how much “boost” are we talking about here anyway? The specs claim that the Boostaroo Revolution will put out up to 32mW of power (both channels driven) and 11.5 dB in gain with headphones up to 300 ohms. 300 ohms, it turns out, is precisely the impedance of my Sennheiser HD-650’s, which, with a lowish sensitivity of 103 dB, and absolutely gorgeous sound, proved to be the perfect cans to test with.

Boostaroo also hypes a feature they call “imaged surround sound”, which, they claim is created by their “patented circuit [which] breaks apart compressed audio signals into three separate audio channels. This effect not only produces a highly defined sound, but creates imaged surround sound as well.” I’m not sure exactly what “imaged surround sound” is but it sounds like it might be an attempt to imitate Headroom’s Crossfeed feature, which aims to make headphone listening more natural sounding by mixing some of the left channel signal into the right channel and vice versa, thereby helping to approximate how we hear without headphones. Either way it sounds like some kind of matrix circuit intended to make sound from the Boostroo more spacious.

Ipod on Steroids

Despite its silly name and clunky design the Boostaroo Revolution did, thankfully, acquit itself nicely when it came to driving the big Sennheisers. The sound through the Boostaroo was greatly improved from that of my iPod Mini on its own, especially in the bass. Bottom end firmed up dramatically with far greater control and impact. Dynamics too were vastly improved, as one would expect with more power. In general the sound just came to life in a way that my iPod couldn’t muster on its own. Transients had more snap, drums had more slam, mids had more presence and palpability and the overall result was much more involving music. Switching back to the output of the iPod resulted in flat and flaccid sound which, with lower volume source material, often had insufficient gain even with the volume cranked all the way up.

By way of comparison I just happened to have the Headroom Microstack available. The Microstack consists of Headroom’s Micro DAC and Micro Amp, designed to be used together to extract the best possible sound from both computers and portable audio players. With no digital out on my iPod the DAC wasn’t relevant here, but the Micro Amp aptly demonstrated what US $299 gets you vs. $60. The Headroom unit not only had far more gain (and a volume control) it was smoother and more refined sounding in every way (especially up top). It exercised even greater control of the big 650’s, producing deeper, better delineated bottom end with power and authority to burn. It was amazing just how immersive yet smooth, dynamic, powerful and airy this combination sounded. Nothing like putting US $800 worth of electronics and headphones downstream of a $200 iPod! The Micro Amp, however, is quite a lot larger and heavier than the Boostaroo, although it can also run on battery power.

Pairing the Boostaroo with the much more efficient and easily driven FS1 in-ear monitors from Xtrememac was much less transformative of the sound. The bottom end did stiffen up a little bit and there was a little more snap and sparkle, but the improvement was far more modest than with the Sennheisers and the extra sensitivity of the phones made the Boosteroo’s noise floor jump further into the foreground. In fact, the Sennheisers sounded so much better I quickly went back to listening to them anyway (I later tried the Boostaroo with a pair of Ultimate Ears Superfi 5 Pro in ear headphones and had similar results. In fact, these headphones are so sensitive that they made the Boostaroo’s noise floor even more audible, which manifested itself as a steady hiss). As for the promise of “imaged surround sound”, I never heard anything that sounded much beyond good old stereo. With no way of switching their “patented circuit” off I had no reliable way of knowing just what it was doing to the signal. The audiophile purist in me suspects the Boostaroo might sound better without it. A defeat switch, much like the crossfeed switch on the Headroom Micro Amp, would be a welcome addition.

So while it can be something of a pain to use and cart around, the Boostaroo Revolution can coax mighty impressive sound from a portable music player into difficult to drive headphones, sound quality quite disproportionate, in fact, to its US $50 price tag. If you’ve invested some money in decent headphones and want to hear what an iPod is capable of, the Boostaroo Revolution is a very good way to find out.

Aaron Marshall

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