The SF-1 can be fitted into any tubed guitar/bass amplifier on the market. Its applicability is "limited" to about 99% of existing models both in and out of production. As shipped, the SF-1 operates with supply voltages up to 900Vdc. Since most amps operate at 500V or less, there are few compatibility issues.

The board-level "Full-scale" trim adjustment fine-tunes the Power Scale function by setting the maximum output voltage and aligning the corresponding power level with the "10" position for the Power Scale pot itself. This eliminates a top-end dead spot in the sweep of the PS pot while accommodating amps of any supply voltage. Screen voltage is typically a bit less than plate voltage, and the "Screen-trim" allows Vs to be as low as 52% of Va. Replacing one of the screen-trim pots with a fixed resistance allows Vs to be far less than half of Va - a required modification for SF-1 use in Univox amps, some Ampegs, Fender PS-series, and others. There is also a trim adjustment to set the precise bias proportion, in addition to the chassis-mountable bias pot.

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 can be switched using any method (series or shunt) and use any technology of switching (jfets, CMOS, BJTs, LDRs and relays) Multiple PS selection is directly compatible with ERK (Electronic Relay Kit) and QRK (Quad Relay Kit).

A "drive compensation" and bias pot are provided. Multiple bias pots can be paralleled to the one provided, with each controlling an individual tube or circuit half.

The SF-1 uses small, non-critical pots, allowing easy placement of these components on a crowded front panel. Those supplied are 16mm.

Adding the VCK (Voltage Clamp KIT) to maintain a constant voltage to the non-scaled circuits helps to maintain tone consistency from loud to quiet, and also provides clean power to those low-level audio circuits. SF-1 requires a low- to medium-impedance bias supply of high output voltage for proper performance. If the stock amp does not have such a bias supply, add the RBX (Raw Bias Auxiliary supply) to assure a problem-free installation.

PCB dimensions: 3.5 x 1.5", 89 x 38mm