There are a several small caveats to note:
• The iStreamer is not portable (it’s tethered to its wall wart-type power supply).
• The iStreamer does not provide digital audio outputs, so that there’s no way to use it as a digital dock to feed data to an outboard DAC.
• The iStreamer can be sensitive to the condition of the Apple dock/USB cable, so that you’ll want to make sure the connectors are in good shape and correctly inserted on the Apple end (the iStreamer may not be able to achieve or maintain proper sync if the connector is seated askew in the Apple device).
• In a break with the common practice, the iStreamer’s data sync lights flash on and off continuously when sync is achieved (for most other DAC makers, a flashing light indicates that the DAC is trying to sync, while a solid light indicates that data sync has successfully been achieved).
• Finally, note that while the iStreamer supports many Apple devices (as listed below), it does not support some of the earlier generation iPods (I believe because they may not support the iStreamer’s required host mode interface).
None of these caveats constitutes a “showstopper” by any means, but they are certainly points worth bearing in mind for prospective iStreamer buyers.
• iPod touch (1st, 2nd, 3rd and 4th generation)
• iPod classic
• iPod nano (1st, 2nd, 3rd, 4th, 5th and 6th generation)
• iPhone 3G
• iPhone 3GS
• iPhone 4
• iPad 3G
In general, I found the iStreamer offered smooth, neutral tonal balance with solid but not exaggerated bass, a good measure of midrange openness, and very smooth highs that seemed to be rolled off just a hair. For many listeners, these characteristics point toward a DAC that is eminently musical—never cold, brash, brittle-sounding, or analytical. The benefit, of course, is that the iStreamer lets users completely bypass the slightly raw, coarse-sounding sonics of Apple’s own DAC and analog audio electronics to step up to a whole different (and better) class of performance.
But the iStreamer’s signature characteristic is an uncanny quality of rock-solid stability, which manifests itself as a sonic sense of purity of timber and “locked-to-a-clock” rhythmic precision. Another benefit is a certain desirable quality of ease in the iStreamer’s presentation. I can’t say for sure, but I believe these positive qualities may very well be attributable to the HRT’s “jitter-free host mode interface.”
I put the iStreamer through several sets of comparisons tests, with outcomes as noted below.
For this comparison I conducted three sets of tests, always using the same set of lossless, CD-resolution files stored on an iPod Classic. All listening was done through Ultimate Ears In-Ear Reference Monitors.
I began by listening to the iPod Classic connected directly to a pair of Ultimate Ears IERM's. Next, I used Moon Audio Silver Dragon line out dock (LOD) cable to connect the iPod Classic to an ALO Audio Rx Mk II portable headphone amplifier. Finally, I inserted the iStreamer in the signal path, connecting the iPod Classic to the iStreamer and then used the iStreamer’s analog outputs to drive the ALO headphone amp.
• iPod Classic + High Quality Headphones: The iPod did a decent job with the Ultimate Ears ‘phones, which are reasonably easy to drive. Even so, I noted a few shortcomings. First, bass was not as deeply extended or well-controlled as I would have liked, mids were somewhat forward-sounding and a bit splashy, while fast-rising, high-energy treble transients had a subtly aggressive, “pingy” quality that inexperienced listeners might mistake for “detail,” but that wasn’t really right.
• iPod Classic + Portable Headphone Amp + High Quality Headphones: The iPod Classic gave significantly better performance when used with a high quality LOD cable and portable amp, exhibiting improved bass performance and smoother, better balanced, and more open-sounding mids and highs. But, even with the help of the cable and amp, the iPod still showed slightly less extended bass than would be optimal, residual hints of midrange forwardness, and highs that—though greatly improved—still showed traces of splashiness and a subtle lack of focus.