The Centrance Hi-Fi M8 is a rather unusual product on a number of counts, starting with the fact that it's offered in eight different connectivity configurations that were proposed by potential buyers who responded to a crowdsourced thread on the Head-Fi Web site. I admire Centrance's willingness to accept consumer opinions, but as it turns out most consumers opt for the configuration I have for review, the HiFi-M8 XL4, which features 3.5mm, 6.3mm and four-pin XLR headphone output jacks on the front panel. Some of the other versions are directed to pro users with headphones that don't have standard 3.5mm or 6.3mm jacks. The HiFi-M8 was designed and made in the US.
The HiFi-M8's rear panel's switches present four sound tuning options: impedance, gain, treble, and bass. I've seen bass and gain controls on a few digital converter/headphone amps I've tried before, but the HiFi-M8 is the first to have impedance and treble adjustability. The gain switch changes the HiFi-M8's volume capability with different types of headphones. In any case, with the HiFi-M8 you can more easily zero in on exactly the sound you want. HiFi-M8 models have USB and iPad/iPhone/iPod inputs; the HiFi-M8 LX models replace phone/iDevice connectivity with a Toslink digital optical input. Android compatibility isn't guaranteed, but Centrance recommends the USB Audio Recorder Pro app that allows the phone to play audio. The Centrance Web site has more information about the different HiFi-M8 configurations. They're all the same size, just 1.3x3.25x5.25 inches.
All HiFi-M8 models can be used at home with the included AC power supply, or on the go with its internal battery. At home the HiFi-M8 will charge your phone or tablet while it's playing music. The Hifi-M8's digital converter handles up to 24-bit/192 kHz high-resolution audio.
I was intrigued by the Hifi-M8's impedance switch, you can select between 1, 2, and 10 ohm output impedance settings, and it was easy to hear that the 10 ohm setting softened the sound with my Shure SE846 in-ear headphones. The 1 and 2 ohm settings sounded far more detailed. That said, some users may prefer the 10 ohm setting for its richer balance, but it's easy enough to try different settings and decide for yourself which sounds best.
To get a fix on the HiFi-M8's sound I compared it with my iPod Classic's headphone jack. To evaluate the Hifi-M8's sound it was hooked up to the Classic's digital output and listened to with a set of Hifiman RE-600 in-ear headphones. The first thing I noticed was the imaging, it was bigger and more expansive with the HiFi-M8. As I listened more, the difference in clarity became apparent, the cymbals and other percussion instruments' shimmer and sparkle were impressive. This was with standard Apple Lossless files, but they sounded more like high-resolution, remastered tunes. Goosing up the bass on the HiFi-M8 contributed a deeper foundation for the music, without losing bass definition. Returning to the iPod solo the sound was murky and dead. What a comedown!
The HiFi-M8 also sounded amazing with my Hifiman HE-6 full-size headphones. These headphones are so hard to drive they can't be used with iPods or phones, only the most powerful home headphone amps let the HE-6s sing, so I was shocked by what this battery-powered amp could do. The HE-6 is a remarkably transparent-sounding headphone, and now with the HiFi-M8, I can take this incredible headphone on the go.
My high-impedance (250 ohms) Beyerdynamic T70 is another headphone that isn't at its best with phones or iPods, but the HiFi-M8 allowed them to really strut their stuff. The T70 can sound thin at home with some AC-powered headphone amps, but with the HiFi-M8 they sounded sweet! With the amp's bass boost switch in the mid position the T70 delivered remarkably solid, very deep bass. These headphones never sounded better.
So if you've already invested in a great set of headphones, but are still plugging them into your phone, iPod, or home computer you're missing out on the sound quality you paid for, the HiFi-M8 can take you there.
All eight versions of the Centrance HiFi-M8 sell for the same price: $700 direct from its Web site and authorized dealers. As with other high-performance headphone amps I've reviewed, the HiFi-M8 only makes sense for folks who already own at least one set of great headphones. If you don't yet have stellar 'phones, hold off on the HiFi-M8. The first order of business is getting the best headphones you can. '