The Woo Audio WA7 Fireflies is one of the most beautiful audio products I've ever used. For my money it approaches a level of design grace comparable to that of Apple products. The 5-inch cube headphone amplifier has two vacuum tubes protected by a thick glass cover. The WA7 also has a built-in 32-bit/192kHz USB digital-to-analog converter (DAC) and lots of custom-made parts, including dedicated nickel alloy output transformers. There's a 6.3mm jack for home-style headphones, and a 3.5mm jack for portable ones. That's noteworthy, as few headphone amps have both jack sizes. The silky feeling volume control, the solid aluminum chassis, and the thick glass top cover all impart a quality feel. The WA7 runs a bit warm to the touch.
An impedance switch on the rear panel allows the user to optimize the WA7's sound for low (under 70 ohm) or high impedance (over 70 ohm) headphones. Stereo RCA analog inputs are also provided so you can listen to external sources, such as a radio or a higher-quality DAC like my Schiit Bifrost. The WA7's separate, 2.8 pound AC power supply is larger than the amp! The WA7 is available in silver or black finishes for $799 through Monday, January 28; after that date the price goes up to $999.
I first auditioned the WA7 with its built-in USB DAC and liked what I heard. Switching over to my $449 Schiit Audio Bifrost DAC produced a more transparent sound with the amp.
My first impression of the WA7 was this little amp sounds powerful. Bob Marley's In Dub, Vol. 1 CD had remarkable impact and weight. The music sounded so good I listened louder than usual for me, and the sound never grew strained or harsh. The Fleet Foxes' ethereal voices and the reverberation surrounding them were majestic over my Audio Technica ATH M50 headphones. The acoustic tunes had the warmth I associate with the sound of live music.
The WA7 is one of the few home headphone amps that sounds great with full-size and in-ear headphones. I don't know why that is, but my big Hifiman HE-500s, Ultimate Ears UE900, and Jerry Harvey JH13 in-ear headphones were all at their best with the WA7. If you've only heard headphones plugged into a phone, the WA7's sound will blow your mind. The UE900s were considerably more powerful, more dynamically alive; its bass definition was firmed up, and the treble was clearer and more precise with the WA7.
The WA7 also really clicked with my Audeze LCD 2 headphones; there was real synergy there. The soundstage was huge, extending well outside the ear cups.
To put the WA7's sound in perspective, I compared it to my solid-state Burson Audio HA-160 amp, which had a leaner and cooler tonal balance. With bright sounding headphones like the Sennheiser HD 700 or Grado RS-1, I much preferred the WA7. With more neutral ones, like the Beyerdynamic T 90, I liked the HA-160. Both amps are excellent but have a different sonic "flavor."
The Woo Audio WA7 Fireflies is sold direct from the company with a 20-day return guarantee, but there is a 10 percent restocking fee.