Rolls Corporation Rolls FX953

The Rolls FX953 is a preamplifier pedal from Rolls Corporation built around an unusual idea: instead of hiding bias error, it deliberately over-biases or under-biases its preamp circuit to produce level and distortion effects. Rolls describes it as born from the company's extensive experience in biasing amplifiers and preamps, and the manual calls it a versatile preamplifier pedal designed to replicate the effects of intentionally over- or under-biasing a preamp¹².

At its core are custom-designed class A preamplifiers that Rolls says are meticulously crafted to emulate the characteristics of a tube amp, both under and over biased. A low pass filter control is designed to replicate the distinctive tonal characteristics of different bass guitar cabinets, letting a player shape the top end the way a cabinet choice would².

Bias as a tone control

In most amplifiers, incorrect bias is a fault. The FX953 treats it as a feature: the primary function of the pedal, per the manual, is to intentionally manipulate a circuit by either over-biasing or under-biasing it, producing the level and distortion effects that come with each condition². The specification sheet underlines how far that goes:

In other words, the pedal is designed to be pushed well into distortion territory rather than to stay clean².

The Out knob sits outside that system. The manual states that it sets the output level of the FX953, that it is not part of the bias, and that it is only for level matching, so it is the control to reach for when fitting the pedal into a rig rather than a tone control².

Specifications

Power and connections

The FX953 runs on either a 15 VDC adapter or a single 9V battery. The box includes²:

• 15V power supply (PN PS27s)²
• Owner's manual²

Connections are a single 1/4" input, with outputs on a mono XLR balanced jack and a 1/4" jack, so the pedal can feed an amp and a PA or recording input directly².

The footswitch is described as an active switch with true bypass, so the preamp circuitry drops out of the signal path when the pedal is off².

Bass first, guitar welcome

Rolls designed the FX953 around bass: the low pass filter exists to mimic the tonal character of different bass cabinets, and the manual notes the pedal was initially tailored for bass guitar applications. The same manual states that the FX953 is compatible with any guitar, so a six-string player can use the same bias and filter controls². Players comparing it with other bass-oriented gear may also want to look at the wider field of Bass Pedals and Overdrive Pedals, since the bias circuit here produces distortion-style effects from a preamp rather than a dedicated drive pedal.

Questions