PSU-TPA - Power Supply for Tube Power Amp: PCB Only


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Tube power amplifiers require various voltages for the plate circuit, bias and heaters. PSU-TPA provides an integrated power supply solution that is compact while providing extremely clean support for tube audio circuitry. These supplies are so good we use them in our own London Power amplifiers!

PSU-TPA accommodates wiring for world-wide mains compatibility using an offboard 115/230V range switch. The board itself supports the following:

  • dual mains fuses
  • plate supply up to 450Vdc
  • active hum filtering for high-voltage plate supply
  • bias supply for fixed-biasing
  • 6V/12V London Power heater system
  • DC stand-off for heater supply (linkable option)
  • regulated ±DC auxiliary supply
  • optimized ground tie to chassis

The paralleled main filter cap positions can be any snap-mount type with 10mm lead spacing and diameter up to 35mm, such as the Panasonic TS-series or Nichicon LS-series. Either cap position may be used, or both can be used, depending on the application requirement. The output filter position allows a maximum diameter of 25mm. Other cap positions on the board accommodate a wide range of possible values and types. Most voltages required for London Power's tube power amp kits such as the PA66 require 450Vdc or less, fitting in well with available capacitors.

These low-noise power supply units (PSUs) can be used to support large numbers of preamp tubes, such as for a mixer or multi-channel active cross-over.

The London Power 6V/12V heater configuration allows the actual heater wiring to be small-gauge wire, typically #20 or #22. Otherwise, the traditional 6V-only heater wiring can be accommodated. In either case, a DC-stand-off is provided for a 30db reduction of heater noise.

The bias supply is a typical cascaded RC filter following a full bridge. Proper bias supplies are built using separate windings, as all London Power power transformers (PTs) have.

The auxiliary supply provides active regulation of both polarities, supporting opamps and other solid-state devices, and switching circuitry.

PSU-TPA is optimized for use with London Power's PTs, which have dual primaries, plate and bias windings that use a full bridge rectifier (not a half-bridge), CT-ed auxiliary and the 6V/12V heater winding. Hobbyists may choose to use alternate PTs, mixing several units to achieve the required supply support.

Doubled output wiring blocks are provided to facilitate connection of multiple power amps, preamps and auxiliary circuits. All wiring should be #22 twisted as appropriate. Transformer leads should be #18 or smaller.

Extra fuse blocks are recommended, as it is highly beneficial to protect every secondary and also to protect each output stage. Use only slow-blow fuses around the power transformer and fast-blow types for output transformers.

PSU-TPA's PCB measures 6" x 3.5" (155 x 89mm)

PSU-TPA: Printed circuit board only. See below for other options.

Add GND Ground-Link-Isolator to avoid ground loops with other mains-powered equipment.

Other PSU-TPA Packages:

PSU-COMP: Printed circuit board plus all components.

PSU-10: PSU to support 10W tube PA

PSU-25: PSU to support 25W tube PA or 2x 10W stereo PA

PSU-50: PSU to support 50W tube PA or 2x 25W stereo PA

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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PO Box 10012, Thunder Bay, ON P7B 6T6 CANADA