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Douk Audio F5 HiFi Vacuum Tube Amplifier, Pure Class A Single-Ended Stereo Amp Review

A pure Class A single-ended tube amplifier at $459.99: 6L6 output tubes and a 6N1 driver deliver 6W+6W into 4 or 8 ohm speakers, fed by a 150W transformer and a no-feedback ultra-linear output stage.

3.83.8 out of 5 starsUpdated October 14, 2026
$459.99Price checked October 14, 2026
Check price at Douk Audio
Douk Audio F5 HiFi Vacuum Tube Amplifier, Pure Class A Single-Ended Stereo Amp

Our verdict

The F5 is a $459.99 pure Class A single-ended tube amplifier for listeners who prioritize tone over power. A 6N1 driver and a pair of 6L6 tubes produce 6W+6W into 4 or 8 ohm loads, backed by a 150W transformer and a 15W ultra-linear output stage run without large-loop feedback. The result is described as warm, rich and full, with tube-rolling options from EL34 to KT66. Two things matter before buying: speaker efficiency, and confirming the mains voltage, since the 110V version is currently listed as unavailable.

Best for
Tube enthusiasts with efficient passive speakers who want authentic single-ended Class A sound on a desktop-scale budget.
Skip if
Your speakers are low-sensitivity, you need digital or phono inputs, or you can't confirm the correct mains voltage.
Check price at Douk AudioHow we research

The Douk Audio F5 is a vacuum tube power amplifier priced at $459.99, built around a pure Class A, single-ended circuit. It measures 230 x 205 x 160mm and weighs 6.57kg, and it is designed to drive passive home speakers from up to two analog sources over stereo RCA, selected with an input switch on the chassis.

The tube complement is a high-current double triode 6N for voltage amplification and a 6L6 for single-ended power amplification, feeding speakers through banana jacks tapped at 4 or 8 ohm. Douk Audio describes the resulting sound as warm and rich, full and thick in the mid-bass, and transparent and smooth in the treble, with the tube stage filtering digital harshness, reducing noise and improving dynamics. Because the sockets are pluggable, the 6L6 tubes can be exchanged for 6P3P, EL34, 6550 or KT66 types, and the 6N1 for 6H1 or ECC85, to explore different sound styles.

The transformer set is where the money goes. A 150W large power transformer feeds a 15W no-large-loop-feedback ultra-linear output transformer, wound with a unique cross-composite method that greatly reduces leakage inductance. The result, per Douk Audio, is sufficient power to easily drive most home passive speakers from the 6W+6W output. Frequency response spans 35Hz-25kHz with an 88dB signal-to-noise ratio, 750mV input sensitivity and 100K input impedance. Build details include a 0.35mm imported iron core, an APLS potentiometer and imported capacitors in a silver aluminum chassis.

One purchase-critical detail: the working voltage is listed as AC 220V, with the 110V version noted as not available currently, so buyers on 110V mains should confirm the voltage situation with the seller before ordering. The box contains the amplifier and a power cord.

Douk Audio ships worldwide with free and expedited options, and the cost varies by destination country. Packages under 2kg go by airmail (10-25 days); heavier orders ship via DHL, UPS or FedEx (5-8 days). Import duties or customs charges are the buyer's responsibility. The store offers a 30-day free return or full refund and a 1-year warranty on all items, excluding orders placed by mistake, man-made damage or misuse, subjective change of mind, and anything outside the warranty terms.

What we liked

  • Genuine tube topology: 6N double-triode voltage amplification feeding 6L6 single-ended Class A power tubes
  • 150W power transformer and a 15W ultra-linear output transformer using a cross-composite winding method to reduce leakage inductance
  • Warm, rich voicing described as full and thick in the mid-bass with transparent, smooth treble
  • Two stereo RCA inputs with a selector, plus tube rolling options like 6P3P, EL34, 6550 and KT66
  • Solid silver aluminum chassis, APLS potentiometer and 6.57kg of build for a desktop-sized amp

Worth noting

  • At 6W+6W, this single-ended amp wants efficient speakers; low-sensitivity bookshelf models may struggle
  • The listing states the 110V version is not currently available, so buyers on 110V mains should confirm voltage with the seller before ordering
  • It is a power amplifier with analog RCA inputs only, and there is no phono stage, DAC or Bluetooth on board

Questions before you buy

How much power does the F5 deliver?

6W + 6W into 4 or 8 ohm speakers, in a pure Class A single-ended configuration with a 150W power transformer and a 15W ultra-linear output transformer.

Which speakers suit it?

Douk Audio says the transformer set provides sufficient power to easily drive most home passive speakers, but at 6W+6W the F5 pairs best with reasonably efficient speakers.

Can I change the tubes?

Yes. The pluggable sockets accept 6P3P, EL34, 6550 or KT66 in place of the 6L6 power tubes and 6H1 or ECC85 in place of the 6N1 driver.

What is the return and warranty policy?

Douk Audio offers a 30-day free return or full refund and a 1-year warranty. Exclusions include orders placed by mistake, man-made damage or misuse, and subjective change of mind.

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