Volume pedals are volume potientiometers set into a rocking foot treadle, so that the volume of the bass guitar can be changed by the foot. While electric basses have a volume potentiometer on the front of the instrument, during some musical passages, the bass player needs both hands to perform, so they may not be able to change the volume knob with their hand. For the double bass, the volume pedal allows the performer to change the volume without having to change the volume on their amplifier or preamplifier. Compression pedals affect the dynamics (volume levels) of a bass signal by subtly increasing the volume of quiet notes and reducing the volume of loud notes, which smooths out or "compresses" the overall sound. Limiters, which are similar to compressors, prevent the upper volume levels (peaks) of notes from getting too loud, which can damage speakers. Noise gates remove hums and hisses that occur with distortion pedals, vintage pedals, and some electric basses.
In the 1990s and 2000s, bass distortion effects became widely available. These effects contained circuitry which ensured that the low-range bass signal was maintained in the distorted bass tone. Bass distortion is used in genres such as metal, thrash, hardcore, and punk.
Bass "overdrive" effects use a vacuum tube (or digitally-simulated tube modelling techniques) to compress the top of the signal's wave form, giving a smoother distorted signal than regular distortion effects. Regular bass distortion effects preamplify the signal to the point that it develops a gritty or "dirty" tone.
Fuzz bass effects are sometimes created for bass by using fuzzbox effects designed for electric guitars. Fuzzboxes boost and clip the signal sufficiently to turn a standard sine wave input into what is effectively a square wave output, giving a much more distorted and synthetic sound than a standard distortion or overdrive. Paul McCartney of The Beatles used fuzz bass on "Think for Yourself" in the 1966 album "Rubber Soul. The bassist for Muse, Chris Wolstenholme, often uses bass fuzz in the band's songs, most notably the single Hysteria, and along with delay in the single Time Is Running Out.
Filter based effects for bass include equalizer, phase shifter, wah and auto-wah.
A bass equalizer is the most commonly used of these three effects. It adjusts the frequency response in a number of different frequency bands. While its function is similar to a tone controls on an amplifier, such as rudimentary "bass" and "treble" frequency knobs, it allows for more precise frequency changes. A rack-mounted bass equalizer, for example, may have ten sliders to control the frequency range encompassed by a regular "bass" frequency knob.
In comparison with an electric guitar equalizer, a bass equalizer usually has a lower frequency range that goes down to 40 Hz, to accommodate the electric bass' lower range. Some bass equalizers designed for use with extended range basses go even lower, to 20 Hz. Equalizers can be used to change the tone and sound of the electric bass. If the instrument sounds too "boomy", the bassist can lower the frequency which is overly resonant, or if there is too much fingernail or pick noise, the higher frequencies can be reduced.
Notch filters (also called band-stop filters or band-rejection filters) are sometimes used with double basses. Notch filters are filters that allow most frequencies to pass through unaltered, while attenuating those in a specific range to very low levels. Notch filters are used in instrument amplifiers and preamplifiers for acoustic instruments such as acoustic guitar, mandolin, and bass instrument amplifiers to reduce or prevent feedback. While most notch filters are set manually by the user, there are also automatic notch filters which detect the onset of feedback and notch out the frequency before damaging feedback begins.
Bass Phase Shifters create a complex frequency response containing many regularly-spaced "notches" in an incoming signal by combining it with a copy of itself out of phase, and shifting the phase relationship cyclically. The phasing effect creates a "whooshing" sound that is reminiscent of the sound of a flying jet.
Bass Wah pedals are a band-pass filter set into a rocking foot treadle, so that it can be operated by the foot, which is designed for the frequency range of the bass guitar. In the fully depressed position, the wah pedal (or "wah-wah pedal") allows only a small portion of the incoming signal's higher-range frequencies to pass through the filter. Rocking the pedal back and forth alternately allows lower and higher frequencies to pass through, which creates a "crying" effect similar to a person saying "wah".
Auto-Wahs are a Wah pedal without a rocker, controlled instead by the dynamic envelope of the signal. An auto-wah, also called an envelope filter, uses the level of the guitar signal to control the wah filter position, so that as a note is played, it automatically starts with the sound of a wah pedal pulled back, and then quickly changes to the sound of a wah pedal pushed forward, or the reverse movement depending on the settings.
Time-based effects include delay/echo, chorus and looping.
Delay or Echo effects create a copy of an incoming sound and slightly time-delay it, creating either a "slap" (single repetition) or an echo (multiple repetitions) effect. Bassists who have a prominent solo role in the bands they play in (such as jazz fusion bassists) use time delay pedals to add a very short delay (in effect, a reverb sound) to their fretless bass playing.
Bass chorus effects use a cycling, variable delay time that is short so that individual repetitions are not heard. The result is a thick, "swirling" sound that suggests multiple instruments playing in unison (chorus) that are slightly out of tune. Bass chorus effects were more common in the late 1980s, when manufacturers such as Peavey included chorus effects in its bass amplifiers. In the 1990s and 2000s, more sophisticated bass chorus effects devices were created which only apply the swirling chorus effect to the higher parts of the bass tone, leaving the instrument's low fundamental untouched.
Looping pedals have extremely long delay times, which allow performers to record a phrase or passage (such as a "riff" or "groove") and play along with it. This allows a solo performer to record an accompaniment or ostinato passage and then, with the looping pedal playing back this passage, perform solo improvisations over the accompaniment. Jazz fusion bassists and jam band bassists have used looping pedals in live performances. Fusion bassist Jaco Pastorius uses a looping pedal for his song "Slang", and solos over the backing parts he records on the loop.
Some pitch related effects are octavers and pitch shifters.
A bass octaver mixes the input signal with a synthesised signal whose musical tone is an octave lower than the original. This allows bass players to "thicken" their sound by creating parallel octaves to the bassline that they are performing. In the 2000s, this effect was integrated into some higher-end preamplifiers and amplifiers. Octave effects can also be used to provide an extended low range for bassists who do not have a 5-string or 6-string bass.
A pitch shifter is a device that alters the pitch of the instruments. They are often used with an expression pedal to give a smooth portamento-like effect. Pitch shifting pedals can also be used to transpose a bassline into a different key.
A multi-effects device (also called a "multi-FX" device) is a single electronics effects pedal or rackmount device that contains many different electronic effects. In the late 1990s and throughout the 2000s, multi-FX manufacturers such as Zoom and Korg produced devices that were increasingly feature-laden. Multi-FX devices allow several of the effects to be used together, and most devices allow users to set "preset" combinations of different effects. This allows bassists to have quick on-stage access to different effects combinations.
Multi-effects devices designed specifically for electric bass reconfigure the effects so that they are compatible with the electric bass' low range and include electric bass-oriented effects such as a fretless bass simulator effect or a bass synthesizer. Some multi-FX pedals for bass contain modelled versions of well-known effects pedals or bass amplifiers.
Multi-effects devices have garnered a large share of the effects device market because they offer the user such a large variety of effects in a single package. A low-priced multi-effects pedal may provide 20 or more effects for the price of a regular single-effect pedal. However, most multi-effects devices give the user less tonal options and control for individual effects than a regular single effect device. As well, while the sound quality of lower-priced multi-effects devices is acceptable for live performances, it may not be suitable for recording.
Bass players who use a number of bass effect pedals may use a pedalboard to organize, transport and protect their effects pedals. Pedalboards are special holders or padded cases made of plastic, wood, or aluminium to which the effects pedals are attached with velcro, form-fitted foam, or other techniques. A pedalboard is laid flat on the stage for use during a performance, and it usually has a removable cover which protects the pedals during transportation. Many pedalboards can be plugged in so that they can provide nine volt power for the effects pedals.