The SF-2 can be fitted into any cathode-biased amp with a plate supply up to 900Vdc. A "Full-scale" trimpot sets the top-end of the PS pot to match the amplifier, eliminating a dead spot in the sweep of the PS control while accommodating nearly every cathode-biased tube amp ever made. Vintage amps ranged up to 500V, where most modern cathode-biased guitar amps operate below 400V.

The screen supply (Vs) is typically a bit lower than the plate supply (V), but can be as low as 52% of Va using the "Screen-trim" pots. For Vs lower than this, replace one of the screen-trim pots with a fixed resistor. The screen output is not needed with triode power stages, or with ultralinear-wired stages such as the peavey VTX-series, Fender Mk2-style amps (70W Super; 135W Twin).

Multiple PS pots are readily added and switched in multi-voice amplifiers. Any type, brand, style or wattage of pot can be used in the PS position. These controls have very little voltage across them, so any switching method (shunt or series) can be used, and any technology for the switching (jfets, CMOS, BJTs, LDRs or relays). SF2 is fully compatible with ERK (Electronic Relay Kit) and QRK (Quad Relay Kit) for PS switching.

A "drive compensation" pot is provided.

The SF-2 uses small, non-critical pots, allowing easy placement of these components on a crowded front panel. Those supplied are 16mm.

Adding the Voltage Clamp Kit (VCK) maintains a constant voltage to the non-scaled circuits, helping to maintain tone consistency from loud to quiet. It also provides clean power to those low-level audio circuits.

PCB dimensions: 2.65 x 1.5", 68 x 38mm