The Truth Shall Make You Free
August 10th, 2012 -- by Chris Martens
Dr. Alex Cavalli builds world-class headphone amplifiers partly as a business, but largely as a labor of love. He doesn’t seek to build a lot of amplifiers, but by his own admission hopes that the ones he does produce will win critical acclaim and, more importantly, will find their way into the hands of owners who will cherish them as classics in their own time. Thus far, Cavalli has gotten part of his wish; last year, Playback reviewed Cavalli’s first production headphone amplifier, the Liquid Fire, and pronounced it a “state of the art” component (words we do not use lightly). Moreover, the Liquid Fire has sold well, so that each of Cavalli’s typically small production batches has sold out thus far. Now, Dr. Cavalli is back with a new and even more ambitious product, the Liquid Lightning solid-state electrostatic headphone amplifier ($4250). Why an amp for electrostatic ‘phones, which are relatively uncommon and quite expensive? The short, two-word answer is this: sonic excellence.
We at Playback think, as do many other high-end headphone experts, that the best headphone presently available is the Stax SR-009 electrostatic “Earspeaker” (Stax’s term, not ours), as reviewed in Playback 54.But great though the SR-009 is, its sonic character almost defies description because, as we noted in our review, “the underlying sonic ‘persona’ of the SR-009 can and does shift in both subtle and profound ways as you connect these headphones to different amplifiers and source components.” We went to say that, “the sound of the Stax will always be an uncannily revealing and nuanced rendition of the signature sound of whatever components you happen to use to drive them.”
During a recent conversation Dr. Cavalli told Playback that his primary motivation in creating the Liquid Lightning was to build the finest electrostatic amp he knew how to design—one that would be, in a sonic sense, “essentially colorless.” Another goal, though, was to create an amp that would perform optimally without requiring any of the painstaking “tube rolling” activities often associated with tube-powered designs. (Cavalli is actually a great fan of tube-powered amplifiers, but concedes that they probably aren’t for everyone.). Has Cavalli succeeded in making a headphone amplifier so accurate and faithful to source materials that the only sonic “personality” listeners would hear would be that of the music itself. We think so, but read on for more details.
- Many world-class electrostatic headphone amps are either tube or hybrid tube/solid-state designs, but the Liquid Lightning is a purely solid-state design that uses innovative circuit technology to extract extraordinary performance from high voltage MOSFET devices. Cavalli says, “MOSFETS are more durable than bi-polar junction transistors and can be run at higher power levels in the same space.”
- The Liquid Lightning uses high-quality parts throughout, such as a TKD Quad Fader volume control, plus more than a few elements custom made for this amp, including:
- A custom piezo-type power switch,
- A custom RCore transformer, and
- Custom made Stax configuration output jacks, which, unlike many competing Stax-type jacks, are precision made to grip Stax connector plugs very firmly and prevent any possibility of users receiving shocks (Stax electrostats reququire 580V bias) when accidentall pressing their fingers against the jack openings.
- Output: The Liquid Lightning has 400V power supply rails, meaning it can yield an output swing of 1600V peak-to-peak, which Cavalli notes is “a standardized way of specifying the output voltage excursion of electrostatic amplifiers”.
- The amp has a gain of 500x in single-ended mode, or 1000x in balanced mode.
- Provides switch-selectable single-ended and balanced inputs.
- Provides two output jacks, with bias of 580V for Jack 1 (Stax Pro bias), and the owner’s choice of 580V (Stax), 540V (Sennheiser HE60), or 500V (Sennheiser HE90) for Jack 2.
- The amp has an input impedance of 45k Ohms per signal, which—notes Cavalli—“means that in balanced mode both plus and minus signals are each terminated into 45k Ohms.”
- The amp power supply has a standby mode and an overload sensing circuit that “monitors the power (current) being used by the amplifier section.” Cavalli adds that if, “usage exceeds a pre-determined amount (because the amplifier is drawing too much current) the power supply turns the Liquid Lightning completely off.”
- Power cycling safety features: Cavalli points out that “one additional advantage of the power supply is that if there is a power blip (even a very short one) the amp turns off and will not turn on again when power returns. It requires the user to push the switch again. This prevents rapid power cycling that can sometimes damage amplifiers due to fast transient power interruptions.”