This little Sony will pump up the sound of your headphones

I have to hand it to Sony -- the PHA-2 is far and away the best-looking portable headphone amplifier/digital converter I've seen.

Its sleek extruded metal casework feels like it can take a beating, and the front "handles" don't just look cool -- they protect the volume knob and headphone cable from accidental bumps. It's smaller than most competing amps, but the PHA-2's sound is big and brawny. It's a little powerhouse. I mostly listened to the PHA-2 mated with my iPod Classic , but it can also work as a USB digital converter/headphone amp with your computer or tablet.

I listened with a bunch of high-end headphones, starting with a Sony MDR 7520, then a NAD HP50, a Sennheiser HD 580, a HiFiMan HE 400 , and a Bowers & Wilkins P5; they're all full-size headphones. The PHA-2's sound had a weight and warmth that flattered every music genre. Resolution of fine detail was good, though if you're looking for a lean or bright sound that emphasizes "detail" the PHA-2 will disappoint. Its softer and sweeter sound doesn't hype the treble.

Moving to in-ear headphones, with the Ultimate Ears UE 900, my impressions of the PHA-2's sound didn't change. That low-end fullness was, if anything, even stronger. The PHA-2 adds considerable oomph to the bass and dynamic punch. The UE 900's sound was energized by the PHA-2. Returning to the sound available from the iPod Classic's headphone jack was a major letdown.

Connectivity options include USB Micro-B input (for charging), USB Mini-B input (for Sony Walkman), USB Standard type A (for iPod, iPhone , and iPad ), plus the 3.5mm headphone jack and 3.5 mm analog jack.

The analog jack is switchable between input and output, and the PHA-2 only supports Android devices over the analog input. The PHA-2 can play MP3, ALAC, 192kHz FLAC and DSD high-resolution files. Maximum playtime is just 6.5 hours. The amp measures a trim 2.67 by 1.14 by 5.5 inches (68 by 29 by 140mm), and weighs 4.2 ounces (119 grams).

With hard-to-drive, power-hungry headphones, like my 300-ohm Sennheiser HD 580, the PHA-2 really shined. The HD 580 can sound dull and lifeless with some amps, but the sound of Daft Punk's "Random Access Memories" album was anything but. The HiFiMan HE 400 is another challenging headphone. But again, the PHA-2 upped the ante, sound-wise. Deep bass was nice and firm, and drums' lively dynamics were given full reign.

Pitting the PHA-2 against another portable amp/converter, the $700/£560 Centrance Hi-Fi M8, was an interesting study in contrast. The mellower-sounding PHA-2 took the edge off harsh recordings, but with great recordings I appreciated the Hi-Fi M8's superior see-through transparency. The sound was more exciting than the PHA-2. That one has less treble resolution and texture than the Hi-Fi M8.

I liked both units, but in the end preferred the Hi-Fi M8. Still, the PHA-2 is smaller, a little more affordable, and definitely more attractive.

It's available now direct from Sony for $600 in the US, and from online resellers in the UK for around £350, or around AU$490 in Australia.