First Listen: Cavalli Audio Liquid Fire Hybrid Headphone Amplifier

Posted by: Chris Martens at 5:05 pm, April 13th, 2011

Over the next several issues, Playback’s monthly email newsletters will be devoting some extra attention to headphone amplifiers, where I will evaluate some models and my colleague Tom Martin will evaluate others.

One particularly exciting new offering (and a model that Tom Martin will eventually review) is the new Cavalli Audio Liquid Fire hybrid headphone amplifier, which I first covered last June in a blog I wrote after attending the Head-Fi.org Can-Jam event in Chicago, in June 2010.

At the event, I saw and heard an initial prototype of the Cavalli Liquid Fire, which seemed very promising. Now, Playback has on hand a pilot production sample of the final version of the amp, which Dr. Alex Cavalli is manufacturing in Austin, TX and will be selling (at least for the initial production run of 20 units) for $2750/each.

Technology Backgrounder

As mentioned above, the Cavalli Liquid Fire is a hybrid headphone amp, meaning that it uses a combination of tube- and solid-state-powered output circuitry. While hybrid circuits, per se, are not new, there are several aspects of the Cavalli design that are quite unusual and distinctive.

• First, the Liquid Fire uses an entirely DC coupled hybrid circuit, meaning that there are no capacitors in the signal path at all.
• All voltage amplification is handled purely by tubes, where the tube complement includes four JJ Tesla 6922 tubes—each of which has burned-in for 25 hours prior to shipment of the amp.
• The tube section of the amplifier is fed by its own dedicated 100V power supply.
• A precise, 20-second tube heater delay circuit (with color-coded LED indicator lights) ensures that tube warm-up is complete before the tube circuit is fully engaged.
• A combination of conventional and MOSFET transistors handles all power output amplification. (The MOSFET output stage is biased at 100mA and runs in Class A almost all of the time.).
• The solid-state section of the amplifier is fed by a separate, dedicated 30V power supply.
• An opamp servo circuit ensures that DC offset is held at 0VDC.
• A precise, 20-second output delay/DC offset detection circuit (again with color coded indicator lights) ensures that power output circuitry is properly warmed up, and DC offset is properly set at 0VDC, before the headphone output jacks are enabled.
• Key amplifier components (chassis enclosure, RCore transformer, piezo-electric power switch) are US made.

The amp strives to provide a best-of-two-world’s design, combining the transparency, harmonic richness, and sonic liquidity of great tube circuits with the cleanliness, precision, and control of great solid state circuits; hence the name Liquid Fire.

Appearance/Changes

Those who saw and heard the Cavalli Liquid Fire prototype and CanJam Chicago 2010 will immediately notice three things about the production version Liquid Fire:

• It’s much smaller than the prototype was.
• It’s arguably even more beautiful than the prototype was.
• It sounds even better than the prototype did.

Unlike some tube amps, which cultivate a deliberately retro, son-of-1950’s-vintage-McIntosh-amps vibe, the Cavalli Liquid Fire is a distinctly and pleasingly modern design. The moderately sized amp (14” x 10” x 3.5”) is housed in a satin black enclosure that sports two front panel-mounted tube viewing windows, upon which is imprinted Cavalli’s signature “yin/yang” logo. (If you look closely, one side of the yin/yang panel features the schematic symbol for a vacuum tube, while the other features the symbol for a transistor.). Way cool.

The (to-my-eyes) Ferrari-esque theme of the design highlights two colors: satin black and gloss red. Thus, the Cavalli name and the Liquid Fire name are spelled out in bright red letters, and the amp’s slick piezo power switch, volume control knob, and main circuit board are similar done up in red. As the tubes warm up, red LED pilot lights on the main circuit board begin to glow, providing background illumination for your tube-viewing pleasure.

The Sound

I need to be careful, here, since I don’t want to take any thunder away from Tom Martin’s upcoming review of the Liquid Fire. So, rather than providing a detailed analysis of the amp’s sound, let me simply provide some initial (though I think also lasting) impressions.