You wouldn’t have thought the word ‘portable’ could be contentious, would you? And I suppose it isn’t, not in absolute terms. After all, if a piece of electronic equipment (just as a ‘for instance’) is battery-powered, and can be easily lifted and moved from point ‘A’ to point ‘B’, then by definition it’s ‘portable’.
‘Portable’ as it relates to a DAC you might use to improve the sound quality of your smartphone, though, is a different matter. This EarMen TR‑Amp, for example, is a portable DAC/headphone amp that is undoubtedly capable of far more convincing and gratifying sound than any (and I mean absolutely any) smartphone is able to deliver by itself. But while its dimensions (30 × 66 × 129mm) and weight (240g) don’t suggest a device that’s difficult to transport, it’s significantly bigger and heavier than any smartphone it might accompany. Once it’s physically mated to your smartphone using its USB-C input, don’t imagine for a moment it won’t ruin the line of your jacket.
Mind you, when you consider the way the TR-Amp is specified it’s a surprise to find it’s not the size of a paperback book. At one end of the aluminium enclosure there are a pair of USB-C inputs – one is for data, the other for charging the 3700mAh battery (the TR-Amp is good for around 10 hours of use between charges), and they can be used simultaneously. There’s a pair of RCA outputs for connection into a static system, and a toggle switch to select between line-level and pre-amplified output. At the other end there’s an unnecessarily large gain control, plus 6.3mm and 3.5mm headphone outputs – these, too, can both be used at the same time.
On the inside, EarMen (a sister company to Auris Audio) has fitted the TR-Amp with TPA6120 Class AB amplifier architecture by Texas Instruments. The intention is to deliver low noise, lower distortion and sky-high on-demand current when the going gets properly dynamic. It’s also designed to allow gain-independent frequency response, so full amplifier bandwidth is available even with the volume tap fully open. EarMen reckons the TR-Amp can consistently serve up 400mW of power into 16ohms – which means there isn’t really a pair of headphones around it can’t drive comfortably.
Digital-to-analogue conversion is handled by an ESS ES9038Q2M Sabre DAC augmented by the same company’s HyperStream II Quad architecture and Time Domain Jitter Eliminator. The upshot of this flurry of exciting-sounding features is a DAC that’s ready to handle all PCM audio formats up to 32bit/384kHz resolution, MQA, and native DSD128 as well as DSD256 via DoP.