VCK - Voltage Clamp Kit


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VCK Voltage Clamp Kit stabilises voltages in a tube preamp, helping to keep tone consistent with fluctuations of incoming power. This is particularly important in cathode-biased amplifiers fitted with Power Scaling.

  • maximum input voltage: 550V (most cathode-biased amps are 400V or less)
  • maximum input/output voltage difference: 200V
  • trimpot allows easy voltage setting
  • modest hum reduction of 22dB typical

Cathode-biased amplifiers pull full power even at idle and this pulls the supply voltage down to a value that it stays at more or less even when the amp is driven to full output. In a Power Scaled cathode-biased amp, as the Power Scale control is dialed down, the supply voltage will rise as it becomes "unloaded". This will change the tonal contribution of the preamp at low-power settings. Adding VCK to stabilise the preamp voltage to the stock "loaded" value will keep the tonal contribution of the preamp constant with any Power Scale setting.

The unloaded voltage in a cathode-biased amp can be 20% higher than the normal idle voltage. VCK is designed to minimise this rise of voltage and keep tone the same.

VCK can be used in other situations where the incoming supply voltage varies due to, say, poor mains regulation in the locale. 

VCK has been designed to occupy as little space as possible in the amp chassis, requiring less than one-square-inch of space (1"x1", 25x25mm)

The kit requires assembly, and includes all the components that go on the PCB, the PCB, and notes for installation and set-up. 
NOTE: If you would like VCK assembled, add VCK-BLT.
NOTE: If you are ordering VCK with SV2 or SB84 and are having those kits assembled , SV-BLT will cover the assembly of VCK as well.

PCB size: 1.4" x 1", 36mm x 25mm

About London Power

London Power was founded in 1990 by Kevin O'Connor, after two decades of research into innovative audio amplification techniques. Kevin is an audio designer, author and speaker, known for his proprietary methodology called Power Scaling, and for his eleven books on audio subjects. Whether you seek amps, kits or information, you'll find useful answers here on not just the "how" but the "why" of audio amplifier design. Please enjoy the information on this site, and don't hesitate to contact us with questions.

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