Power Management Kits

PSK Power Scaling Kits     PSK-1    PS Kit #1   $145 PSK-PC PS Kit #1 with PCB   $156 PSK-2    PS Kit #2   $100 Printer-friendly PDF

Power Scaling is a proprietary technology developed by London Power that allows the output power of an audio amplifier to be dialed down from 100% to less than 1%. This requires a modification to the amplifier's power supply. Unlike external attenuators or load boxes, which interfere with the amp-speaker interface, the installation of Power Scaling does not alter the sound of the amp. Each PSK includes a 'Drive Compensation' control to retain the interface between the output stage and the splitter. Power Scaling is easily applied to all pentode, tetrode, triode or ultralinear output stages, and preamps too. Get more information from the Power Scaling Q&A page. These kits should be installed by experienced hobbyists or experienced techs. The PSK circuit is built into the amplifier. For situations in which a less invasive solution is needed, use the PS-BOX Power Scaling Box. Three separate Power Scaling kits are available to accommodate every existing tube amp: The PSK-1 can be used in any tube amp made, up to 160W. For control over the individual tube bias, add the appropriate BMK Bias Mod Kit to control either the push and pull halves of the circuit, or each tube individually. The PSKpc is functionally identical to the PSK-1, but includes a printed circuit board. This incorporates a fan supply. The simpler PSK-2 is designed for cathode-biased amps. For very large amps of 300-400W or more, the PSK-1 is combined with the THS Tracking High-Voltage Supply. In amplifiers that can use the PSK-1 or PSK-2, tube life will be greatly enhanced by the Power Scale circuit. Large amplifiers using the PSK-1 will have only slightly extended tube life, unless the THS Tracking High-Voltage Supply is added. Either PSK-1 or PSK-2 kit can be combined with an output filter, fusing and connectors to form a bench power supply with typical test-lab connectors. The  FTC Fixed-to-Cathode package allows the PSK-1 circuit to switch to cathode bias operation. The PMS Power Mode Switch allows two operating modes with either the PSK-1 or PSK-2. The PSB Power Scale Boost kit can be added to any PSK for a volume boost at the output stage. Independent Power Scale controls are available using the PS-Dual, PS-Triple, and PS-Quad multiple Power Scale control kits. All PSK-kits include the front-panel Power Scale control and Drive Compensation control. The PSK-1 generates its own raw bias supply and incorprates a tracking bias regulator for fixed-bias output stages. PSK-2 has no bias supply or regulator, as it is used with cathode biased amps only. It can also be used to control preamp voltages, and makes a great complement to the PSK-1 controlling the power stage. With PSK-1 or PSK-2, two different operating modes are possible through the basic wiring allowing just the power stage to be varied, or the whole amp to be varied. The PSK-1 generates its own raw bias supply for use with the output stage. The PSK-2 can be converted into a PSK-1 at a later date using the TBS Tracking Bias Supply. The PSK-kits are tied between the main rectifier output and the filter caps, providing an active current limit to protect the transformers, caps and tubes. The PSK-1 is rated for 600Vdc. The PSK-1 is trated for 400Vdc and less, typical for cathode-biased amplifiers.  The PSK layouts are for eyelet board construction, and the card materials and instructions are available in the CCK Circuit Card Kit. Perf-board or PCBs can also be used. The PSKpc is identical to the PSK-1 but includes a printed circuit board (PCB). The main card size is 3.75" (86mm) by 4.25" (108mm), supoorting the B+ regulator and bias supply, while the fixed-B+ card is 1.5" (38mm) by 3.9" (74mm). The main card's long dimension can be reduced by 0.25" (6mm). In very large amps with screen supplies much different than their plate supplies, the PSK-1 provides control over the screen and bias voltages and the THS regulates the plate voltage. Amps built this way includes: Trace Elliot VA-400; Fender PS-400; older Hiwatt 400W models; Ampeg SVT and V-9.         For more info, read our Power Scaling Kit FAQ!