If the battery low indicator blinks briefly as the jack is unplugged, that can be a normal sign that the battery is being disconnected.

As the circuit powers down, the voltage passes through the indicator threshold and the LED may flash momentarily.

This suggests the battery switching is probably working correctly.

Remove the feet and take out the four screws. Very early units may not have these screws.

Use a stiff, thin-edged tool to carefully prise between the base and side wall. It does not need to be sharp.

The base sits in a groove around the sides. Once both sides are freed slightly, the base can be pulled out.

The plate version of the Marcus Retro is intended for four-string Marcus signature basses and is not suitable for the five-string plate.

For a five-string version, the non-plate Marcus Retro may be fitted to the existing plate, but the knob spacing may require slight hole modification.

If the pickup toggle is also installed, an additional hole may be required.

The stock Marcus-style preamp is only part of the sound.

Marcus Miller’s recorded tone also depends on the bass, pickups, strings, technique, amplification, recording chain and additional EQ used after the instrument.

The Marcus Retro is designed to get closer from the bass itself by adding useful low end, presence, bright function and mid sweep control.

The Battery Low Indicator shows when the battery voltage is falling toward the end of useful life.

The warning starts while some useful battery life remains, giving time to replace the battery before failure during use.

The indicator uses extremely little current, so its effect on overall battery life is insignificant.

The BTBM-01 combines the BTB bass/treble control with a two-input mixer stage.

The mixer allows two separate signals, such as magnetic pickups and a piezo preamp, to be mixed electronically without the compromise of simple passive mixing.

It is useful where two sources need to be combined correctly before further processing.

The MID SWEEP 01 is a standalone midrange control module.

It can be used on its own or cascaded with other modules. The sweep range is switchable on the circuit board using DIL switches, giving two overlapping frequency ranges.

It is useful where a focused adjustable mid control is required.

SPM modules are single-pot EQ modules that can be combined according to the installation requirement.

They allow bass, mid and treble sections to be selected and arranged in a more custom way than a standard preamp assembly.

Internal frequency controls allow the EQ to be tuned to the instrument and player preference.

The MPB-01 combines a piezo input stage with a four-input mixer stage.

The piezo section includes gain trim and provision for high-frequency roll-off. The mixer section allows magnetic and piezo sources to be combined correctly.

It is intended for more complex instruments using multiple magnetic and/or piezo signals.

Occasionally we have graded plates available. These are new plates with minor cosmetic marks or finish issues.

In most cases the marks are very small and only noticeable on close inspection. Once the plate is fitted and in normal use, ordinary handling usually makes these marks much less noticeable.

Availability changes, so graded plates should be treated as occasional stock rather than a standard product option.