PSU-100 - Super-Quiet Power Supply for 100W Tube Amp


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PSU-100 is a super-quiet power supply that can support 100W-worth of tube audio power amplification.

  • Japan-compatible universal mains:100V,120V,240V
  • toroidal power transformer (PT) for low EMI
  • active hum filtering for plate supply
  • regulated auxiliary supplies for opamps or switching circuits
  • 6V wiring for power tubes
  • 12V wiring for preamp tubes
  • DC standoff for heater circuit
  • individual fusing for primaries and secondaries
  • ground-link-isolator to eliminate ground loops
  • plate supply: 470Vdc at 2100mAdc
  • bias: -84Vdc supports Power Scale regulatorsaAuxiliary: +/-12Vdc at 175mAdc
  • heater: 6V/12Vasc London Power wiring at 10A
  • heaters support 8-octals plus 24x 12A_7
  • ...or heaters support 4-octals plus 45x 12A_7
  • ...or heaters support 2-octals plus 56x 12A_7
  • ...or heaters support 56x 12A_7
  • PCB: 6" x 4" x 2.25" (153 x 102 x 58mm)
  • PT-100: 5.8" dia x 2.6" high (148 x 66mm) 4.6kg

PSU-100 is a sophisticated power supply for tube power amplifiers, offering super low noise and proper grounding. Only linear techniques are used, along with through-hole component construction to assure reliability and ease servicing. This is the same type of power supply unit (PSU) that London Power uses in its music-industry (MI) tube amps, but it is also designed to support hifi and broadcast-quality amplifiers. We believe noise should be banished from all of these applications; PSU-100 meets that end.

PSU-100 has a massive main filter, assuring extremely long life even at high ambient temperatures. This filter is followed by an active hum filter and another over-sized passive filter, pushing hum and noise through this path to inaudible levels. Plentiful wire blocks are provided to connect up to four power amplifiers plus various preamps, with dedicated wire groups to each.

The heater supply is truly massive with a 10A capability using London Power's 6/12 wiring system - the equivalent of a traditional 6V system at 20A! Expect no shortage of heater power, as even with eight octal power tubes one can tie in up to 24 12A_7 preamp tubes. Reducing the number of power tubes increases the number of small-signal tubes that can be supported, to the extreme of ALL-12A_7s at 56 tubes. Of course, one can use 6V preamp tubes as well, taking note of their current demands and wiring them accordingly. A DC-stand-off assures that hum via the heater wiring path is kept very low.

An onboard auxiliary supply provides +/-12Vdc at 175mA for relays, opamps, switching systems, etc, as modern amplifiers often have.These are regulated rails, so no noise should get through to sensitive audio circuitry.

Onboard links allow proper Galactic Grounding to be followed with respect to how the heaters, bias and auxiliary supplies are referenced to the plate supply. The built-in ground-link-isolator (GND) assures that there is a proper audio system ground when PSU-100's supported circuitry is used alone, while also assuring that no ground loops will be created when connected to other mains-operated equipment.

PSU-100 provides on-board fusing for mains, plate, auxiliary and heaters. This makes the PCB a bit larger but provides convenience for isolating circuits during initial testing or repair.

The double-sided printed circuit board is of high quality with twice the standard weight of copper. Through-hole components enforce the use of "human scale" parts that real people can handle and install, and assures that reliability can be more readilly achieved. A standard IEC mains connector is used, and the builder should acquire a detachable mains cord to suit his or her locale.

Universal mains compatibility is achieved by following the various wiring options in the kit note.

PSU-100 requires assembly. If you would like to receive PSU-100 pre-assembled, add PSU-BLT to your order. This covers assembly of ONE PSU-100.

PSU-100 includes the PCB, all components that mount on the PCB, an IEC power-entry socket, power switch, LED and holder, two ground lugs, and PT-100 toroidal power transformer with mounting hardware.

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