To read the full review: http://www.avguide.com/review/cavalli-audio-liquid-fire-headphone-amplifier-playback-45
What it is: A US-made, hand-built, ultra high-quality hybrid tube/solid-state headphone amplifier of minimalist architecture. The amp provides a single, line-level single-ended stereo analog audio input with two single-ended ¼-inch phone jack-type headphone outputs. One of the amps two output jacks features an output impedance of ¼ ohm, while the other can be configured to provide the user’s choice of ¼, 50, or 100 ohm output impedance (a detail touch we find near-brilliant). The amp uses four JJ Tesla 6922 tubes for voltage amplification, with a combination of conventional and MOSFET transistor for all other amplification. Very high quality parts are used throughout.
Why you might choose it: To state things simply, this is the first and thus far the only product that Playback has ever described with this coveted four-word phrase: state of the art. What makes it a state of the art component? For starters, the Liquid Fire offers neutral voicing, which means that the amplifier imparts no discernible sound of its own (what you hear is what the recording presents for you to hear—no more, and no less). Next, the Cavalli is an absolute ace at retrieving low-level signals, meaning it lets you hear way down deep into the innermost recesses of well-made recordings. Third, the Liquid Fire offers astonishingly realistic instrumental separation, never smearing instruments together no matter how complex a recording might be. Finally, and this is the tricky part, the Cavalli does all of the above without losing the inherent smoothness, richness, and warmth of well-recorded music. Last but certainly not least, the Liquid Fire can drive just about any headphone on the planet, no matter how power hungry it might be or how “difficult” a load it might present.
Why you might look further: We can think of only two reasons to look further. The first is that the Cavalli might be too pricey for your budget (we feel the Liquid Fire is worth the money, but there’s no denying that hand-made products of this caliber come at a price). Second, you may find that—for your specific application—the Cavalli’s sonic neutrality and honesty (which are for the most parts “plusses” in our book) may not give ideal results with your chosen headphones. In particular, if you favor an amp that, in subtle ways, makes the midrange of the music sound more vivid or intense, you might prefer either the Apex or the Woo. But no matter what, do give the Cavalli a listen if top-tier sound is your objective.
To read the full review: http://www.avguide.com/review/woo-audio-wa-22-headphone-amplifier-playback-43
What it is: The WA22 is the next-to-the-top model in Woo Audio’s extensive family of high-end headphone amplifiers. Like all Woo amplifiers, the WA22 is a tube-powered design, and in this case is a fully balanced, transformer-coupled design.
Alone among the three amplifiers referenced here, the WA22 can support headphones wired either for single-ended (that is, traditional ¼-inch phone jack-type) outputs, or wired for use with balanced outputs (as supported by either single four-pin or dual three-pin XLR connectors). What’s the significance of supporting balanced outputs? Many high-end headphone aficionados feel that top-tier headphones simply sound better when wired for balanced mode operation (although there is not universal agreement on this point). Happily, the WA22 lets you pick and choose your preferred mode of operation at will. Note, too, that the WA22 provides both single-ended (RCA jack) and balanced (XLR connector) analog inputs.
Like the Apex amp, above, Woo’s WA22 can be ordered in standard form ($1900) or with any of the following tube upgrades: hand-picked, matched pair of Sylvania 7236 NOS 1963 power tubes ($120), hand-picked matched pair of Shuguang Treasure CV181-Z/6SN7GT driver tubes ($280), and a Sophia Princess Mesh Plate 274B rectifier tube ($150). So, as with the Apex, you can start out with a standard Woo WA22 and upgrade its tubes over time, or you can order it up fully “hot-rodded” from the factory. It’s your call.