Gramophone Dreams

Woo Audio's 20th Anniversary WA24 headphone amplifier comes in a distinctive, low-slung chassis that welcomes the eye with gentle angular volumes and bright, frosty-surfaced, copper-toned controls. In the always-crowded Woo–JPS Labs–Stax room at CanJam 2025, Woo's new $12,999 flagship caught everybody's eye, sitting on a table next to its similar-looking stablemate, the $8999 WA23 LUNA, a tube-rectified single-ended amplifier that, unlike the new WA24, uses 2A3 tubes.

I asked Woo Audio founder Jack Wu how he came up with this design. He told me, "My brother, Zhidong Wu, designed it. He did all the original drawings. But after that, we worked together, slowly revising and refining those drawings. We started out with a 3D-printed model, then we had numerous revisions leading up to a metal sampling. It was a long process, during which I worked very closely with him. We are both pleased with the results."

What struck me most about the WA24's chassis was that no matter how fabulous it looked with the lights on—no matter how bright and golden that Woo Audio 20th Anniversary badge looked—I thought the amplifier looked more appealing in the dark, where all you see is the halo of orange light surrounding the volume knob, matching perfectly the hue of fire from the 3A/109E tubes' filament cathodes. That's a nice touch, and the kind of intangible that gives its keeper pleasure every day.

With the lights on, I could see that the WA24's four slender tubes were of a type I'd never seen before. A closer look revealed their Stradi brand logos (screened in Western Electric yellow) on Bakelite bases. Under the Stradi logo, the tube identified itself as 3A/109E, a type I'd never heard of (footnote 1). Under that, it said "Made for Woo Audio."

Above the base, I saw a sturdy-looking vacuum tube with sparkling, unusually thick glass surrounding an unusually stout rod-support arbor. Above that were triple micas stabilizing the laddered-grid frame and gleaming pure-nickel anodes. Those nickel plates and the laddered-grid frame (and the spooky purity of the sound) reminded me of the 71A amps I built in the late 1980s. The 71A was one of the clearest-sounding and alluring-looking of all the directly heated triode tubes I experimented with. The WA24 uses two 3A/109Es per channel, operated in parallel, single ended.

My RCA tube manual indicates that the 3A/109E (footnote 2) is built to a common ST16 profile attached to an uncommon B4 base I associate with European PX4 and PX25 tubes. According to Jack Wu, the "E" in 109E indicates it is a "higher gain" version of the 3A/109B, which features a ceramic base. The 3A/109E tubes used in the WA24 Anniversary are premium, new-issue tubes made in Korea by a company called Stradi.

Behind the WA24's copper-toned volume knob lies an Alps RK50 volume control. Flanking it are two smaller, copper-toned knobs. The one on the left offers a choice of higher or lower output impedance. The one on the right is a three-position input selector (two RCA, one XLR).

Flanking those small, copper-toned knobs are a complete set of output sockets: Balanced on the left (4-pin XLR and 4.4mm Pentaconn); single-ended 6.3mm and 3.5mm on the right.

Listening with Meze Elite
I decided to begin my listening with Meze Elite headphones connected to the Woo Audio WA24, sourced by the dCS Lina DAC and Master Clock streaming Andris Nelsons conducting the Boston Symphony Orchestra performing Shostakovich: Symphonies Nos.2, 3, 12 & 13 (24/96 FLAC, DG/ Qobuz). I play this Shostakovich album often, for the sound of its sound. This is a demonstration-quality recording that pushes every audiophile button: big, tight bass; deep, wide spaces; sharp images; crisp highs; startling transients; copious detail.

Then there's the Dmitri factor. Shostakovich's compositional ambitions are well displayed in these symphonies. Watching their thoughtfully engineered matrices unfold is the fun part of this recording. Shostakovich's episodic forms feel modernist avant-garde-ish, but they are melded throughout with bits of fanfare and socio-political seriousness, which the composer felt he must include to satisfy the Soviet demand for populist, nonelitist content. The symphonies included on this DG recording are especially good at pushing and pulling these conflicting imperatives.

With the Lina DAC and Master Clock supplying music to the WA24 amp, the easy-to-drive Meze Elite (32 ohms, 101dB/1mW at 1kHz) presented this recording as though someone created it to be an orchestral showpiece and audiophile demo record: impactful, super-3D, nano-detailed. That is also how it sounded through Voxativ's Hagen2 loudspeakers. Through the Meze Elite and WA24, it sounded fantastic and haute bourgeois.

Listening with HiFiMan's HE-R10P
Who wrote the book of the seven seals?

After the Meze, I decided to change my listening game entirely, choosing a different type of headphone and switching to music with a different world view: Dr. Ethel Caffie-Austin singing "John the Revelator" on The Harry Smith Connection: A Live Tribute to the Anthology of American Folk Music (16/44.1 FLAC, Smithsonian Folkways/Qobuz). This anthology is a star-packed tribute to one of the most respected and influential artists of the postwar era in America: Harry Everette Smith (1923–1991). My first encounter with Smith's art was seeing his trippy, hand-painted 35mm films in art school. Since that day, I've been slowly discovering the originality and importance of Harry Smith's creative and philosophical achievements.

In the music world, Smith's fame and influence as a visual artist are upstaged by the longstanding global reverence for his 1952 Anthology of American Folk Music, a box set of LPs he created from his own collection of 78s for Smithsonian Folkways Records. This collection of 84 old-timey Appalachian, fiddle music, gospel, jug band, blues, and Cajun tunes impacted the music ethos of the 1950s and '60s.

This tribute recording was made in 1997, live at The Barns of Wolf Trap in Vienna, Virginia. I enjoy it because the sound quality is very good, and the performers, including The Fugs, Roger McGuinn, Jeff Tweedy, Dave Van Ronk, John Sebastian, and the above-mentioned Ethel Caffie-Austin, go all-out to show their appreciation for Smith's Anthology.

As I listened...
I was hoping the HiFiMan HE-R10P planar magnetic closed-back would show me how much clarity the Woo WA24's paralleled 3A/109E tubes could manufacture—and these slender triodes seemed right comfortable driving the R10P's 30 ohm impedance. This record, amp, and headphone combo let me roll enjoyably through all 19 tribute tracks with zero thoughts about sound quality. For that achievement, I gave the Woo a perfect score.

In the key of metaphysical distress, the Fugs performing "Nothing"—where they sing about "Quaalude dada" and other surreal-existential absurdities—was a high point of my Woo-review experience. Other than those cool-cat Fug voices, the best part was the ease with which the WA24 + R10P closed-back bypassed hi-fi-ness and foregrounded the Fugs' ironic poetry. That's more evidence that this amp and headphone can disappear. For that, I gave both products a gold star.

I had no other 3A/109E tubes to compare the Stradis to, but in the Woo WA24 these tubes were as thick-glass/high-vacuum clear as any NOS 45 or 2A3 tubes I've used—but the 109E's characteristic sound had a sweeter essence than either of those. The 109Es present sounds in what I perceive as "the tone" of nickel. Creatively, I call this appealing virtue nickeltone, and I also hear it in alnico magnets in cartridges and speakers. I would describe it as a slight haloing that makes vocal and instrumental textures seem polished and gleaming. This could just as easily be the result of the nickel in the output transformers or the nano-crystalline cores of the input transformers, but whatever the cause, this Woo amp sounded the opposite of mechanical. It let each singer's flesh and psyche pass through. While using the WA24, I repeatedly paused and thought, Yep, that's what that record is supposed to sound like.

HiFiMan's HE-R10P was so right-on with the Woo that I decided to see if Ethel Caffie-Austin and the Fugs would fare differently through Linear Tube Audio's Z10e headphone amplifier.

Playing "John the Revelator" with the LTA Z10e powering the R10Ps, I was immediately struck by its rich flavor and relaxed demeanor. The Z10e made the WA24 sound lean. The WA24, though, was dramatically better defined, more refined, and transparent.

When I played The Harry Smith Connection through the dCS Lina headphone amp, I immediately heard the effect of the Lina's lower output impedance, higher torque, and greater raw horsepower. The full black Lina Stack (with Master Clock and the dCS Mosaic app) powering HiFiMan's R10P is as high-rez as I can go in my studio. This source-amp-headphone combo pulled everything out of every track and presented it in a manner that felt wide awake and engaging.

During this three-amp comparison, the R10P closed-back sounded most fit and athletic powered by the Lina amp. With LTA's Z10e amplifier, the R10P sounded rich, vibey, and psychedelic but maybe a touch fuzzy on the edges. Powered by Woo Audio's WA24, the R10P produced its best-ever transparency, disappearing almost completely.

With the ZMF Vérité
The next headphone I tried was ZMF Audio's 300 ohm Vérité closed-back.

The recording I selected was Dis, quand reviendras-tu? by Ukrainian-born French chanteuse Monique Andrée Serf (aka Barbara) (16/44.1 FLAC, BMG/Qobuz). With the Lina-powered ZMF, Barbara's vocals sounded direct and soulful, with plenty of expressive nuance. The Vérité headphones and Lina amp allowed the varied character of Barbara's different microphones to show through, spotlighting the album's physical production, wherein the singer's voice emerges as the chief element in a framework of separately recorded instrumental elements.

The careful crafting of Barbara's suave elocution dominated my attention, presenting well the shifting textures and moody vicissitudes of the artist's delivery. Sound quality felt irreproachable.

Next, I tried Barbara with the closed-back ZMF through the Woo WA24. I was greeted by a sweet liquidity of tone that felt so luxurious that Barbara was no longer an element in a studio recording. Now, she was a woman, with a face and body and an accessible persona. Except for a sense of awe, my critical mind was silenced by the allure of Barbara singing the album's title song: "Dis, quand reviendras-tu?"

This was the moment when all the WA24's tube magic came out. I felt like I was hearing this record like no one had ever heard it before. The form and quality of tube beauty that dominated the WA24-Vérité presentation exceeded any tube beauties I'd previously experienced.

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Footnote 1: Woo Audio, 29 West 46th Street, New York, NY. Tel: (917) 773-8645. Email: info@wooaudio.com. Web: wooaudio.com.

Footnote 2: The 3A/109B is a power/output tube designed for use in telephone repeaters. It is an early tube, apparently introduced around 1925. It had vanished from the RCA guide by 1975.—Jim Austin