PSU-PRE - Power Supply Kit for Tube Preamp


In Stock
Product Code:


PSU-PRE can support up to five12A_7 tubes - enough for a 3-channel preamp with effects loop, consisting of our two preamps LP-PRE and Z-PRE, our LINE output buffer and a BFX loop.

PSU-PRE uses a pair of standard Hammond 229-series transformers to create the heater and plate supplies. Both are DC and well filtered. The plate supply has three nodes that can be individually tapped with paired wiring, for use with preamps other than London Power's. The heater supply can be wired for either 6V or 12V; the latter is preferred for use with our line of preamp kits. The heater supply also supports the switching circuits.

The unregulated heater output can support up to six 300mA heaters at 6Vac or up to six 150mA heaters at 12Vac. It is highly recommended that you use the supplied 12V regulator for the heaters, especially when using less than the full complement of tubes. The regulator assures that the heater voltage will be stable and hum-free. In this wiring, the maximum number of 12A_7s is five.

The plate output is approximately 320Vdc at 37mA. Two supply nodes are provided if some isolation is needed for the circuits attached. Otherwise, use the best-filtered node for the preamp.

World mains compatibility is as simple as moving two jumpers OR by adding a "115V/230V" switch. Wiring for this switch is accommodated by the PCB for players who travel the world.

PSU-PRE includes flameproof resistors, electrolytic caps, fuses and holders, an IEC connector, mains switch and the transformers. Also included are helpful installation notes with schematic and layout diagrams of the kit.

If you would like to receive PSU-PRE pre-assembled, add PSP-BLT to the order.

For the ultimate in low noise, add our QS-LV Quiet Supply active hum filter.

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

For more info on London Power Preamp Kits, see our Selecting a Preamp Kit page.

Need a chassis for your preamp project? See our Rack-Mount Chassis page, or browse under Building Supplies.

PCB size: 5.1" x 4.1" (130mm x 104mm)

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.

Contact Us

(807) 473-0952
11 am - 6 pm, M-F
PO Box 10012, Thunder Bay, ON P7B 6T6 CANADA