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Stereo valve amplifier / chrome version

Velleman K4040: Vacuum Tube Amplifier Kit

Velleman K4040

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DIY Stereo Tube Amplifier Kit - Chrome

The Velleman K4040 Stereo Vacuum Tube Amplifier kit is the ultimate DIY kit in the Velleman kit line up. It is a high-power tube amplifier that offers the deep, rich sounds that are only offered from tubes. The K4040 features high quality EL34 tubes configured in an ultra linear push pull/parallel configuration and ultra-linear over rated output power transformers. Other components include soft start circuit, high quality capacitors, gold plated input and speaker terminals, stand by function and easy bias adjustment with LED indication.

The kit also includes a high quality black and chrome enclosure to give it a professional finished look. The bottom panel is easily removed for access to the circuit board. The K4040 is for the experienced kit builder and requires caution when building and testing as there are high voltages at many points on this circuit. Enrich the audio performance of your hi-fi system with the quality only found with tubes amplifiers and experience the satisfaction of building the K4040 yourself.


  • Assemble your own stereo vacuum tube amp kit
  • Improve the sound of your stereo
  • Comes in a sleek chrome to match any stereo set up


Output Power 2 90 Wrms music power for loads of 4 or 8 ohm
Power Bandwidth 15 Hz - 40 kHz (-3 dB ref. 50 W)
Frequency Range 8 Hz - 80 kHz (-3 dB ref. 1 W)
Harmonic Distortion 0.08% (1 kHz / 1 W) / 0.7% (1 kHz / 90 W)
Signal-to-Noise Ration > 105 dB (A-weighted ref. 90 W)
Channel Separation > 75 dB (ref. 90 W)
Input Impedance 34 Kohm
Input Sensitivity 1 Vrms at 95 W
Damping Factor >10 (100 Hz)
Weight 23.46 Kg
Dimensions 16.7 in. x 5.1 in. x 13.8 in.

Additional Information

Difficulty Level 5
  1. Two amps in one. PP & Class A review by Bartolomew on 7/9/2018

    Best sound great Power.

  2. Sound is awesome review by Fred on 8/30/2016

    I wrote an earlier review when I was 90% done with soldering. In the meantime my Velleman K4040 Tube Power Amp has been completed and is fully functional. The sound is AWESOME. I had very expensive Parasound Halo Amps (like $5K new) and this Amp blows them out of the water, easily. The sound is clearer, warmer, fuller, vibrant, much more transparent, spacial, more complete and with much improved Stereo effect. I hear details I never heard before and the sound is so pleasant, I want to and can play the music a lot louder now too. Great dynamic range! The sterility of the old Amp is gone. Low, midrange and high tones are much improved, the sound is in my face now.
    Best HiFi sound I ever heard! There is a tiny little bit of noise and hum (volume independent and same on both channels) with your ear right in front of the speaker, but 3 to 4 ft away from the speaker, you don't hear it anymore. Definitely a great buy and highly recommended. Go Velleman!

  3. I love it review by Fred on 8/22/2016

    I am 90% done populating and soldering the Board and I love it. Except for that one double Cathode marking issue of one diode on the Board, which is easy to sort out looking at the schematics, everything else is accurate. I am amazed how very accurate everything is, the exact right number and kind of components! And by putting the diodes and resistors in the correct sequence on a strip, it makes it so much easier to put them all on the Board, without having to read all the color codes of the resistors and worry about the different wattages. This was a lot easier then I imagined.
    A very fulfilling and nice project, without any frustration.
    Everything was delivered, not a single item missing and well packaged so that nothing got damaged during transport.
    I look forward to hearing the music through my tube amplifier!

  4. Great value review by Bill on 5/5/2016

    I'm about 40% complete. The instructions are accurate but there are a couple of "speed bumps" (the board indicates both sides of one of the diodes as the cathode) that force the builder to consider and eventually, understand the error in the board 's polarity identification. Looking forward to listening to music through vacuum tubes...

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 Warning: this product can expose you to chemicals which are known to the State of California to cause cancer, birth defects or other reproductive harm. For more information go to: www.P65Warnings.ca.gov/product