My StudyBass

Bass Preamps Part 2

...continued from bass preamps part 1

Effects Loops

On many preamps you will see effects loops. An effects loop sends the bass signal out to some other device or signal processor (like an effects pedal or an instrument tuner). Effects loops have a send (the output) and a return (the input). Your signal is sent to the outboard device, processed, and then returned to the preamp.

Some effects loops allow you to blend the amount of the processed signal with the original signal.


Many preamps have limiters. A limiter limits the overall volume of the signal. Think of it as an adjustable volume ceiling. This is useful to prevent damaging signal levels from reaching other components like your bass cabinet.

Master Volume

One final knob you will see is the master volume. Probably the easiest control to understand, it controls the output volume sent to the power amp.

Bass Preamp Outputs

Preamps have many different types of outputs. Let's look at the most common ones...

Main Output

The main output is sent to the power amp. This may be marked as unbalanced line out.

Bi-Amp Outputs

Some preamps are capable of being bi-amped. Bi-amping means splitting the signal into separate highs and lows. The highs are sent to one set of speakers while the lows are sent to another. This requires a crossover that determines the frequency at which the split occurs. Some crossovers are fixed while others are variable. Bi-amp outputs will be marked high and low.


DI means direct injection. A DI output can be used to send the signal directly to a mixing board or some type of recording device.

Pre- and Post-

You will see many outputs marked as pre-something or post-something. For example, “post-eq output” simply means that the output comes after the eq processing stage. Pre would mean before a particular stage.

Tuner Out

A tuner out allows you to send your bass signal to an outboard electronic bass tuner for….tuning!

Ground Lift Switch

A ground lift switch disconnects the grounding of the preamp. Grounding is an electrical safety mechanism. If there is a surge of power, that surge will be sent to the ground or Earth, instead of through you. Sometimes when equipment or electrical outlets are improperly grounded it can introduce a hum in the audio signal. The ground lift switch is a safe way of disconnecting the ground and possibly eliminating the hum. If you hear a hum, try the ground lift switch if you have one.


Some preamps may have an optional footswitch. The footswitch allows you to control certain settings on your bass preamp. This is useful when your hands are busy playing bass.

Other Bass Preamp Features

Most everything else you will come across will be more specialized EQ-type settings, or effects like chorus or compression. I’ll discuss these in a separate effects section one day. I'll also explain the difference between tube amps and solid-state amps in another article.

Good luck shopping for a bass preamp or bass head!