Woo Audio WA33 Headphone Amplifier and Preamplifier - Silver

Woo Audio WA33 Headphone Amplifier and Preamplifier

What You Need to Know

Woo Audio’s Flagship: Two Chassis, Nine Tubes, No Compromises

The Woo Audio WA33 is the flagship statement from America’s premier tube headphone amplifier builder—a fully balanced, all-tube, pure Class A design spread across two massive chassis and hand-built in New York. It functions brilliantly as both a reference headphone amplifier and a true balanced stereo preamplifier, and it holds The Absolute Sound’s Editors’ Choice Award to prove it.

Available in black or silver anodized aluminum.

All-Tube, Fully Balanced, Pure Class A

Nine tubes do all the work: four 2A3 directly heated triode power tubes, four 6C45 drivers, and a 5U4G rectifier, arranged in a fully balanced push-pull Class A circuit. Signal passes through hand-wound output transformers made in-house, connected by point-to-point wiring—no circuit boards in the signal path.

The sound reviewers describe is glorious: rich, naturally detailed tonal balance with explosive dynamics and powerful, extended bass.

Two Chassis, One Amplifier

The power supply lives in its own chassis, keeping transformer noise away from the delicate audio circuits. Woo’s Internal Coupling Architecture joins the two cases directly—no external umbilical cord—so the WA33 installs as one seamless unit while preserving true dual-chassis isolation.

Power for Any Headphone Made

With up to 10 watts per channel into 32 ohms, the WA33 drives the world’s most demanding headphones—HiFiMan Susvara, Abyss AB-1266—with power and control reviewers call absolutely stunning. High/low impedance and level switches tailor the output from whisper-quiet operation with sensitive in-ears to full grunt for inefficient planars.

The current version even adds a direct current-drive output for true-ribbon headphones—a world first, eliminating the usual interface box. Total range: 0.038 to 600 ohms.

Four Headphone Outputs

The front panel offers a 4-pin XLR balanced output, a 4.4mm balanced Pentaconn, a 6.3mm single-ended jack, and the dedicated TR ribbon output—every connection standard, no adapters required.

A True Balanced Preamplifier

This is no afterthought output jack: the WA33 delivers up to 10V balanced from 50-ohm XLR preamp outputs, with two balanced XLR inputs plus RCA to serve a complete system. The Absolute Sound put it plainly: it’s “a balanced linestage preamplifier suitable for use in the finest audio systems”—and imagined audiophiles using it as the reference linestage in systems costing far more.

Critically Acclaimed at the Highest Level

Beyond The Absolute Sound’s Editors’ Choice Award, the WA33 earned Part-Time Audiophile’s Editors’ Choice Buyer’s Guide nod (“it might just be the best”), while Audio Bacon called it “the best tube headphone amplifier I’ve ever heard” and Enjoy the Music concluded it “will be able to transport them to another world… That the WA33 can double as a preamplifier is icing on the cake.”

Building Your System

Feed the WA33 from a reference balanced DAC via its XLR inputs, and let it pull double duty: headphones by night, balanced preamp into your power amplifier by day. The self-biasing circuit welcomes tube rolling—premium 274B rectifiers are a favorite upgrade—and the PTFE sockets are built for a lifetime of swaps.

Give the tubes open airflow, place it within reach (volume is on the gorgeous TKD potentiometer—no remote), and plan a sturdy shelf: the pair weighs 54 pounds.

Features & Specifications

Fully Balanced All-Tube Class A
Push-pull 2A3 directly heated triodes, transformer-coupled.

Two-Chassis Design
Separate power supply with Internal Coupling Architecture—no umbilical.

Up to 10 Watts per Channel
Drives everything from sensitive IEMs to Susvara and Abyss.

Four Headphone Outputs
4-pin XLR, 4.4mm balanced, 6.3mm, and direct-drive ribbon output.

True Balanced Preamplifier
10V XLR outputs worthy of reference two-channel systems.

Hand-Built in New York
Point-to-point wiring, hand-wound transformers, TKD volume control.

Specifications

•          Type: Headphone Amplifier / Balanced Stereo Preamplifier

•          Topology: Fully Balanced, Push-Pull, Pure Class A, All-Tube

•          Tube Complement: 4 x 2A3 (power), 4 x 6C45 (driver), 1 x 5U4G (rectifier)

•          Power Output: Up to 10W per Channel @ 32 Ohms

•          Ribbon Output: Direct Current-Drive, 3.3A (TR 4-Pin XLR)

•          Headphone Impedance Range: 0.038–600 Ohms

•          Headphone Outputs: 4-Pin XLR Balanced, 4.4mm Balanced, 6.3mm, TR Ribbon

•          Inputs: 2 x Balanced XLR, 1 x RCA

•          Preamp Output: Balanced XLR, 10V Maximum, 50-Ohm Output Impedance

•          Frequency Response: 10Hz–60kHz (-2dB)

•          THD: <0.05% @ 1kHz

•          Signal-to-Noise Ratio: >95dB

•          Volume Control: TKD 4-Channel Balanced Potentiometer

•          Construction: Point-to-Point Wiring; Hand-Wound Output Transformers; PTFE Tube Sockets

•          Dimensions: 17.5“W x 12”D x 13"H (with tubes, both chassis)

•          Weight: 54 lbs

•          Finish: Black or Silver Anodized Aluminum

•          Made In: New York, USA

•          Warranty: 3 Years Limited

Frequently Asked Questions

Can it really serve as my system preamplifier?
Yes—brilliantly. The balanced XLR preamp outputs deliver up to 10 volts from a 50-ohm source impedance, and The Absolute Sound judged it worthy of the finest reference systems. Many owners run headphones and a two-channel rig from the same WA33.

Will it drive my headphones?
All of them. Ten watts per channel handles the hardest planars (Susvara, Abyss AB-1266), the level switch keeps sensitive in-ears hiss-free, and the dedicated ribbon output direct-drives true-ribbon headphones without an interface box—a world first.

What does the Elite Edition add?
The Elite upgrades to single-crystal copper output transformers and internal wiring, an ALPS RK50 volume control, Mundorf Supreme Silver/Gold coupling capacitors, and Cardas/WBT connectors—the same circuit, executed with cost-no-object parts.

Who is the WA33 designed for?
It’s for the listener assembling an end-game headphone system—or a reference two-channel rig—who wants pure Class A tube magnificence, hand-built in America, with the power to drive anything.

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