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The mere mention of big sound-leaking statement cans from Audez'e and Sennheiser plus inefficient HifiMans shows intent well beyond portable convenience. Few will walk the street or use the tube with $2K gigantors on their head. Here the Mk3's lo-gain switch says hello to invisible leakage-proof high-efficiency IEMs or ear plugs. Those types won't risk damage, rip-off, stowaway fuss or complaints from bystanders.

The two long controls with engraved logo and tactile grooving anticipate such mobile use. Then the amp will sit upright clipped to a belt or stick out a pocket. There the original Rx's tiny volume thumb wheel was hard to reach. Now twiddling your knobs in public has never been easier. Perfectly pervy!

That said, the balanced concept aims at ultra performance, not convenience. For that an interface should ideally convert your iDevice's digital output to a balanced analog output. That entails three stacked devices for more size, weight and money. And don't forget the balanced harness. Consumer 'phones are wired single-ended or 3-pole after all.

That means shared grounds between channels. A balanced 4-pole (or dual 3) connection runs dedicated grounds. If your headphone comes with disconnect cabling like Sennheiser's HD-800, all HifiMans, AKG's K-702 and both Audez'e, a replacement harness is a simple mail-order away. More customary hard-wired connections will have to go under the knife, preferably that of a professional modifier who violates original headphone warranties by default. Unless your surgeon is local, you'll also have to ship out. Clearly the RxMk3-b makes greater demands if you want to get out of it all it was designed to deliver.

ALO Audio at the 2102 headfi show in Tokyo

Deliverance: "The 2x2200mHa Lithium-polymer pack makes for quite a big battery with 10-14hr of continuous play. Recharge to full in 3hr. The balanced input currently is for decks like the $299 iBasso balanced portable DAC. For our favored Solo/iPod double we still use our Mk3's SE input. I simply believe that a lot more balanced portable sources will come in the near future. We had to be ready. An interesting note with all the tweaking on the bass feature is that we first thought it wasn't working. A few hours later it was really obvious. Everyone had that reaction. You should tune into the difference shortly. It's very subtle and doesn't molest the signal. We feel that we got it just right.

"Frequency response in both balanced and unbalanced mode is 5Hz-80kHz ±1dB. The lo/med/hi gain settings correspond to -3dB, +3dB and +12dB. Balanced RMS output power with both channels driven is 640mW into 32Ω, 630 into 50, 150 into 300 and 80mW into 600Ω. Unbalanced it's 320mW into 32Ω, 220 into 50, 40 into 300 and 20mW into 600Ω. Bass adjustment at max is +3.5dB@<40Hz, 3dB@80Hz, 2dB@160Hz, 1dB@260Hz, 0.5dB@360Hz and <0.5dB@>360Hz. To obtain a balanced working signal, a non-inverting amplifier buffers the input signal. The output of that amplifier is inverted with a unity-gain amp. The balanced signal is then taken from the outputs of both amps which are contained within the same IC. The worst-case mismatch between inverting and non-inverting outputs is 0.02dB. Going in single-ended is thus no worse than balanced. The real advantage of the RxMk3-b is its fully balanced amplification circuit and ability to drive all headphones in balanced mode."

"As a headfi retailer I've heard practically every portable headphone amp on the market. When you design something with ambitions to be best, it's important to know your competition. I'm thus quite confident that our RxMk3-b is very special. I was fortunate to work with a very skilled team of three gifted engineers who had to translate my wish list and then keep tweaking away at many prototypes until we all signed off on the project. It's been a long road."