R8 000.00
The Velleman K4040 is a high-power stereo vacuum tube amplifier kit designed to deliver a classic “valve sound” with modern reliability. It is notable for its substantial power output, using eight EL34 tubes to produce up to 90Wrms per channel.
Key Features
- Tube Configuration: Uses 8 x EL34 power tubes, 2 x 12AX7 (ECC83) preamp tubes, and 1 x 12AU7 (ECC82) driver/phase splitter tube.
- Operating Class: Operates in Class A for the first 15Wrms, switching to Class AB for higher power levels (up to 95W peak).
- Bias Adjustment: Features an integrated LED indication system that simplifies the process of setting the correct tube bias without needing a separate multimeter.
- Soft-Start Circuit: Includes a switch-on delay for the power transformer to protect and extend the life of the tubes.
- Construction: Available in chrome or black versions, featuring toroidal output transformers and gold-plated terminals.
Technical Specifications
| Specification | Detail |
|---|---|
| Output Power | 2 x 90Wrms (4 or 8 ohms) |
| Frequency Range | 8Hz to 80kHz (-3dB @ 1W) |
| Power Bandwidth | 15Hz to 40kHz (-3dB @ 50W) |
| Harmonic Distortion | 0.08% at 1W / 0.7% at 90W |
| Signal-to-Noise Ratio | > 105dB (A-weighted) |
| Dimensions | 425 x 130 x 350 mm |
| Weight | ~23.5 kg (51.8 lbs) |
Maintenance & Modifications
- Bias Setting: The factory-recommended bias voltage is 0.4VDC measured across the cathode resistors.
- Common Upgrades: Some users modify the circuit to use KT88 or 6L6GC tubes for different sound profiles, though this typically requires manual biasing and may void original support.
- Assembly: The kit is considered “advanced” (level 5), requiring significant soldering (approx. 700 solder points) and careful handling of high-voltage components.