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February 20, 2026
STAX SR-009D Electrostatic Earspeaker
February 20, 2026WES (2nd gen) Electrostatic Headphone Amplifier
RRP 7,000 USD before taxes / £7,000 after taxes. Our trade-in set price: £5,000
*** WE will ship WORLDWIDE ***
Woo Audio WES (2nd gen) Electrostatic Headphone Amplifier, dedicated to working with STAX and other upper-end electrostatic headphones, is the upper echelon, a dedicated power horse to help you hear the best from your precious cans. The one we have for sale here came to us as a trade-in, with STAX SR-009D Electrostatic Earspeakers. Both spanking new and used for the review only, and packed since. Hence, the pictures attached are stock ones, but they are a perfect representation of the unit’s physical condition. It comes boxed, with all the standard tubes included. Because it is a Premium parts build (the units like that are not off-shelf, they are always made to order & customer’s demand).

As our unit is the premium build hence it deserves to be used with the premium tubes as well. Wew tried it with the set of Mullard EL34 Pentodes and a premium quad of 6SL7s (drivers), as well as a pair of a pait of premium Mullard 12AU7 phase spliters (loaded from the back) and a pair of Mullard GZ34 rectifiers(loaded from a front to feed a dual mono PS), we can tell you, the difference isn’t small by any meaning. If you aim to hear that amp at its best, it is rather more like A MUST, thay you MAY. Otherwise, you won’t even hear what you own. We tested it with STAX SR-009D Electrostatic Earspeakers, which we also have on sale on a separate ad. Both can be bundled for the best price. The same applies to the set of tubes. For the bundle shopper, we will make a special PREMIUM TUBES DEAL, for the hald of their market value. Ask are for the prices if you are intertested in optaing one of the best Electrostat energisers in the up to 13k RRP.
Check what the company website says about their WES (2nd gen) below:
Overview
WES (2nd gen) is the ultimate electrostatic headphone amplifier for use with STAX headphones. The new 2nd gen uses a matching quad of output loading chokes utilizing Single Crystal Copper wires (the purest form of copper) with our proprietary winding scheme. The results are a significant improvement in clarity, sound space, dynamic range, and control. WES is a two-chassis system comprising a power supply and a fully balanced amplifier and innovative dual power switch that treats the tubes more gently when starting the unit from cold. Turning on just one of the power switches provides low voltage to the heaters while the WES remains in standby mode. Turning on both power switches allows the unit to operate at full power. WES will reward the listener with reference quality sound without fatigue.

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Updated to 2nd generation in April 2017
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Compatible with 5-pin 580v (Pro-bias) for STAX, Audeze, HiFiMan, MrSpeakers electrostatic headphones
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Tubes: EL34 power x 4, 6SL7 driver x 4, 5AR4 rectifier x 2, 12AU7 phase inverter x 2
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Polytetrafluoroethylene (PTFE) tube sockets
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ALPS RK27 4-channel balanced smooth potentiometer
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Two 12AU7 phase splitter (unbalanced input to balanced input conversion)
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Fully-balanced design, Class-A
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Transformer-coupled, Point-to-Point wiring
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Pseudo-dual power supply
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STAX Pro Bias 5-pin EarSpeakers output x 2
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maximum output 1300Vrms
XLR input x 2, RCA input x 1
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Auricap capacitors for interstage and output coupling
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Mills and Kiwame resistors
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Anodized aluminum chassis, available in black or silver
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Self-biasing with compatible tubes [chart]
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Global voltage (100v–220v) without converter
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Dimensions:
Amplifier (without tubes): 7½”(H), 16½”(W), 12″(D) 20 lbs.,
Power supply unit: 4½”(H), 16½”(W), 12″(D) 20 lbs.,
DC cord length: 18” (end to end)
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Designed and assembled in New York, USA
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Three-year limited warranty [learn more]
The Audiophile-grade premium internal parts upgrade adds the following. * Available exclusively at the time of build.
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V-Cap Oil Damped Advanced Metalized (ODAM) audio grade capacitors for coupling (12 pcs)
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V-Cap Oil Damped Advanced Metalized (ODAM) audio grade capacitors for output (4 pcs)
In the box
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WES (2nd gen) electrostatic headphone amplifier x 1
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WES (2nd gen) power supply unit x 1
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EL34 vacuum tubes x 4
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6SL7 vacuum tubes x 4
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5AR4 vacuum tubes x 2
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12AU7 vacuum tubes x 2
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Umbilical DC cord x 1
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Quick start guide
*AC power cord and audio cables are not included




