RBX Raw Bias Auxiliary Supply Kit provides a high-voltage, low-impedance raw bias supply when such a supply is not readily available in the amp. This allows a cathode-biased amplifier to be given the option of fixed-bias, using the bias switching methods shown in TUT2 (The Ultimate Tone vol.2), or for any situation where the power transformer does not have a bias winding. Add one of our BMK Bias Mod Kits to have adjustable bias for each output tube, along with meter jacks for safe idle current monitoring.
It is also useful when the existing bias supply is too low in voltage or too high in impedance to allow proper support for Power Scaling kits and similar circuitry, such as London Power’s SV1, SV-TT, SUS-1, SUS-3 and TBS kits.
Most tube power amps will require RBX in addition to SV1 for a Power Scale solution. See the SV1+RBX combo page and save! SV1 + RBX Bundle.
For situations where there is a bias winding but the stock bias supply is the traditional half-wave rectified “after-thought”, RBX-LT can be used to create a proper higher-voltage lower-impedance raw bias supply. An popular application is the Marshall 1959, where a proper bias winding is present but the circuitry used will not support a Power Scale regulator.
PCB assembly makes installation quick and easy.
Kits include notes for installation, including schematic and layout diagrams of the kit.
RBX PCB dimension: 3.0 x 2.0″, 78 x 50mm; height with components 1″, 25mm
RBX-LT: dimensions: 1.0″ x 2.0″, 25 x 50mm; height with components 1″, 25mm
RBX: DIY kit with transformer; includes components and notes; requires assembly and installation
RBX-BLT: Assembled RBX with transformer; includes notes; requires installation
RBX-LT: DIY kit with NO TRANSFORMER; includes components and notes; requires assembly and installation
RBX-LT-BLT: Assembled RBX-LT with NO TRANSFORMER; includes notes; requires installation
Not sure whether you need RBX? See our article: “When Do You Need RBX Raw Bias Auxiliary Supply?”