Gramophone Dreams #56: Woo Audio 3ES preamplifier/headphone amplifier and Audeze CRBN electrostatic headphones

At noon on a cloudless, ridiculously bright 97° day, John Atkinson and I auditioned Audeze’s new-but-not-yet-released CRBN electrostatic headphones. The audition took place at a sneak preview hosted by Audeze’s principal, Sankar Thiagasamudram, in a sleeping room at New York’s hipster-chic Ace Hotel on 29th Street and Broadway. Décor in this unusual sleeping room included a bathtub with feet, an antique wood ironing board, a vintage Gibson guitar, and a working stereo system with a Music Hall turntable and an assortment of vintage LPs.

On my way there, I was remembering some of my lifetime experiences with electrostatic transducers. People who know me know that I’ve always been partial to electrostatic loudspeakers and headphones, but I’ve never found any that engage me fulltime, long-term. Over the years, my two pairs of Quad ESL loudspeakers taught me to enjoy the pleasures of a scintillating, perfectly detailed midrange. The original MartinLogan CLS (not the II or IIA) and the Stax ELS F-81 electrostatics took that learning to a higher level: Both speakers thrilled me with their raw, succulent, ultradetailed presentation. Unfortunately, both tended toward odd or gone-missing bottom octaves. Worst of all, they were beamy. And compressed. And staticky. But I loved them anyway.

Likewise, I’ve been drawn to Stax’s SR-009 headphones. I’ve always wanted to love them, but I found the original 009 unsatisfying for daily use. I regard the current SR-009S, which makes proper bass, as one of the most revealing, exciting-to-use headphones of all time.

What I am trying to say is: I’ve been thrilled forever by the quick, vivid beauty of electrostatic transducers, but sooner than later they start sounding like electrostatic transducers. At that point, I go back to the easier flow of dynamic and planar-magnetic headphones and continue my persistent kinships with horn speakers, planar-magnetic panel speakers, full-range speakers on open baffles, and of course my beloved LS3/5a sealed boxes.

I am telling you this because that day at the Ace Hotel I thought the Audeze CRBN electrostatic headphones sounded fresh, open, clean, and abundantly resolved—but more electrostatic and less chunky, weighty, and tone-saturated than I had hoped for. But I wasn’t worried: I blamed the CRBN’s low chunk factor on the Chord Qutest DAC that was sourcing Linear Tube Audio’s Z10e amplifier.

I know the Qutest and LTA’s Z10e from time spent auditioning them for my own reports in this magazine. The Z10e is likely blameless because previously it made the Stax SR-009S, HiFiMan’s Jade II, and Dan Clark’s VOCE electrostats sound smooth, naturally full-bodied, and vivacious. When I put the Qutest in my big system, it sounds smooth and vivacious, too—even elegant—but, I think, a little thin and gray of tone: not hard-bodied and full-textured like my much more expensive reference DACs: the dCS Bartók, HoloAudio May, and the Mola Mola Tambaqui.

As I was leaving that Ace Hotel audition, I arranged to review the CRBN headphones using Linear Tube Audio’s Z10e. Besides powering electrostatic headsets, the Z10e can power conventional dynamic and planar-magnetic headphones as well as regular loudspeakers.

And then, a week later, I found out that Sankar and crew had used Woo Audio’s 3ES electrostatic headphone amp during the development of the CRBN headphones. I had no choice but to call Woo Audio’s proprietor, Jack Wu, requesting a 3ES for my Audeze examinations (footnote 1).

Jack hand-delivered the 3ES one day after the CRBN arrived. As I unpacked the well-packed Woo amp, I spotted its three line-level input pairs on the back (two XLR, one RCA) and their corresponding three-position source-selector knob on the right side of the front panel. Left of the centrally located big knob, which controls the TKD four-channel balanced potentiometer, I spotted the Headphones/Preamp selector knob and my brain exclaimed, “Oh look! It really is a preamp.” When I asked Jack Wu about the 3ES’s circuit, he told me (on the phone) that it was a fully balanced 6SN7 dual-triode differential input, capacitor-coupled to a push-pull 300B directly heated power triode output. The 300B’s cathodes are capacitor-coupled to the 3ES’s balanced XLR outputs. (The 3ES has no single-ended outputs.)

Line-level tube envy
To make sure everybody understands how spectacularly not ordinary this Woo Audio amplifier is, let me restate and clarify what I described above: Besides being a dedicated electrostatic headphone amplifier (with five-pin “Pro” 580V-bias energizing supply that works with headphones from Stax, Dan Clark, and HiFiMan), the Woo Audio 3ES is also a two-chassis, 53lb stereo preamplifier in which the lower, shielded power supply chassis sits on what appear to be premium-quality footers and is fastened to the amplifier-circuit chassis on top via spacers that match the footers on the chassis bottom.

The top of the top chassis displays the 3ES’s quartet (two per channel) of push-pull 300B output tubes. I am auditioning the Standard version, the price of which is $7649. The Standard-version tube lineup is four Psvane 300B directly heated triodes, two Russian-made 6SN7 dual triodes, and a single (Russian) 5U4G rectifier tube. Without tubes, the 3ES measures 17.75″ × 7.25″ × 13.5″. Woo also offers an Elite edition, which costs $11,699 and includes Mundorf Supreme Silver/Gold audio capacitors, single-crystal copper hookup and signal wire, an Alps RK50 four-channel volume control in a brass enclosure, and Cardas Audio XLR and WBT RCA connectors.

To install the 3ES, I simply replaced my reference Rogue Audio RP-7 preamp with the 3ES. The system then featured the dCS Bartók DAC driving the Woo pre via balanced Cardas Clear Cygnus interconnects. Sutherland Engineering’s Little Loco phono stage was connected to the 3ES via single-ended Black Cat Coppertone wires. In turn, the Woo preamp drove the balanced inputs of the Parasound Halo A21+ power amplifier via AudioQuest Mackenzie balanced interconnects.

From the first track I played, that whole shebang motivated my Falcon LS3/5a Gold Badges in a way that I did not anticipate: With the 3ES, the sounds charging my room exhibited a greater force and physicality than they did with the RP-7 preamp. It was an eyebrow-raising moment.

Last month, during my Mola Mola Tambaqui excitements, I discovered how fresh and Windex-clear the dCS Bartók and Tambaqui DACs sounded driving my Elekit and Parasound amps directly, with no Rogue RP-7 in between. Both DACs showcase volume controls that do not appear to color the sound, and both DACs’ output/buffer driver stages supplied enough gain and current capability to keep the sound crisp and vital.

But now, with the Woo 3ES preamp in the system, the character of sound changed, becoming more spirited, more physical, more locomotive-rolling-forward than it was previously, with or without the Rogue RP-7.

To my delight, this new force and density was accompanied by a bright, 300B-fashioned clarity that made my reference preamp seem a tad shadowy. To my further delight, this extra brilliance and physicality was apparent even at the lowest late-night volumes.

The reason I listen to so many simply miked field recordings (by Alan Lomax or David Lewiston, for example) is that they make it easy for me to imagine the in-the-air energy of a live voice or instrument positioned in front of a single microphone.

While I listen to this type of recording, I can ask myself, does the quality and intensity of the sound energy coming out of my speakers resemble that of the energy I imagine went into the microphone?

Footnote 1: Woo Audio, 2219 41st Ave., Suite 502, Long Island City, NY 11101. Tel: (917) 773-8645. Web: wooaudio.com

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