PSX provides an easy interface between London Power’s ERK Electronic Relay Kit and multiple Power Scale controls.
In a 2-channel amp fitted with Power Scaling, you may want two different Power Scale settings to completely distinguish the amp sounds. ERK can handle the preamp switching tasks, but cannot directly switch the Power Scale controls. PSX allows that interface.
PSX includes the Power Scale control, interface circuitry, a jfet to be driven by ERK, and a small PCB that is supported by the control itself.
For a 2-channel amp two PSXs are required.
For a 3-channel amp three PSXs are required.
…and so on.
Note that some means must also be provided to switch the Drive Compensation controls. Usually these require series switching; a relay, such as our RLY Mechanical Relay, is most suitable. To drive RLY from ERK requires adding a BJT and base-stop driven by one of ERK‘s outputs, and powered from the same supply as ERK.
See our Power Scaling FAQ.