A tube amp power supply that’s quiet.
Tube power amplifiers require various voltages for the plate circuit, bias and heaters. London Power’s super-quiet PSU power supply unit 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 amplifiers!
The PCB accommodates wiring for world-wide mains compatibility. The board itself supports the following:
- dual mains fuses
- Japan-compatible 100-120-240V
- plate supply up to 500Vdc
- 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 ±12Vdc auxiliary supply
- optimized ground tie to chassis
The paralleled main filter cap positions provide ample ripple filtering and long life. Most voltages required for London Power’s tube power amp kits such as the PA66-series require 500Vdc or less, fitting in well with available capacitors.
These low-noise 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 +/-12Vdc supply provides active regulation of both polarities, supporting opamps and other solid-state devices, and switching circuitry.
PSU 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.
Standard DIY Kit (PSU-COMP):
Assembly is required; includes PCB plus components that mount on the board, the IEC socket, the mains switch, plus kit notes.
Built Kit (PSU-BLT):
PCB portion is pre-assembled; includes kit notes.
PCB Only (PSU-PCB):
PCB only; includes kit notes.
Standard DIY Kit + 25W Transformer (PSU-25):
Assembly is required. Notes are included. Supports a 25W tube power amp and preamp and is optimally matched to London Power’s PA66-25 and PA66-10 Push-pull Octal Power Amp kits.
- 6V/12V London Power heater system at 5A
- supports four octal tubes plus 12x 12A_7 preamp tubes
- supports ftwo octal tubes plus 22x 12A_7 preamp tubes
- supports 33x 12A_7 preamp tubes without octals
- PSU-25’s power transformer size: 4.6″D x 2.3″H (125 x 63mm)
Built Kit + 25W Transformer (PSU-25-BLT):
PSU-25 with PCB assembled. Transformer fly-leads will not be connected. Notes are included.
PSU’s PCB measures 6″ x 3.5″ (155 x 89mm)