Bassists use their tone to set a song’s vibe. Some chug and dig in to create a bouncy groove, such as AC/DC. Others provide power to the riff or slap lines of funk rock bands like the Chili Peppers.
A bass guitar amp head or amplifier “head” sends output to a speaker cabinet, which can be separate or built into the same unit as the head. Some bass amp heads also feature EQ controls and effects.
Power
A bassist is the backbone of any band, giving the rhythm and character. But the bass guitar wouldn’t sound anything without its speakersaEUR”and the bass amplifier head is what ties the two together. The bass amp head acts as the brains of a bass guitar configuration, providing the preamp to tweak the tone and then the power amp to boost the signal enough to drive the speaker cabinets. The result is the sound the crowd is clamoring to hear.
The type of bass amplifier head you choose depends on your requirements. For example, if you’re playing small gigs with a drummer or in a rehearsal space, then a bass combo amp will provide all the power you need in one unit. But if you want to play larger venues, then you’ll need a high-powered bass amp head that can deliver the necessary volume and sound quality.
Some bassists prefer the sound of tube amplifiers, which can produce a warm, full tone. Other players prefer the punchy, clean sound of solid-state bass amplifiers. Whatever your preferred style, you’ll find a variety of powerful bass amp heads to meet your needs.
When you shop for a bass amplifier head, make sure it’s rated to match your cabinet. For example, if the amp says it outputs 300 Watts at 4 ohms, then you’ll need to match that with a bass cabinet that can handle that amount of power. Otherwise, you’ll overwork the power amp and it will start to burn out.
Many bassists like to pair a bass amp head with a bass speaker cabinet or bass combo amp. This set-up is sometimes called a bass rig or a bass stack, because it consists of a speaker cabinet or combo amp stacked on top of the amplifier head. Alternatively, some bassists like to use a separate bass speaker cabinet connected via a line-level DI out from the amp head. This is often easier to set up and provides more flexibility for different situations. It also allows the bassist to add a distortion pedal for extra grit when needed.
Frequency Response
Bass guitars have low frequencies that need to be reproduced with a greater volume of speaker surface than higher-pitched instruments. This requirement calls for a larger amplifier/speaker cabinet than would be required for other uses, with either a closed back design or a porting mechanism to prevent acoustic pressure behind the speakers from interfering with sound waves coming out of the front.
Most bassists choose to use a tube amp for its tone quality, but solid state amps are also available. The choice depends on personal preference and budget constraints. A vintage Ampeg SVT with eight 10″ speakers, for example, is a favorite among bass guitarists, while the more affordable Yamaha B100-115 combo amp features a 100 watt amplifier “head” on top of an Ashdown 4×10″ cabinet.
The frequency response of a bass amplifier head is determined by the preamp and tone controls that are built into it, as well as how it interacts with a cab. A good quality bass amp will allow the user to sculpt its overall tone to match the type of music being played, as well as the size and layout of the venue where it will be used.
Most modern amps feature an EQ control that allows the bassist to tweak the midrange. The high-mid frequency control is often boosted to compensate for a lack of upper mids in the amplifier’s tone controls. The treble control is another frequently tweaked element of the bass amp. Players can use it to boost the brightness of the tone or to cut the mids to create a darker sound.
Many bassists also like to add compression effects to their amplifiers. This can be done on the amplifier’s panel or by editing a compressor bank within BOSS Tone Studio. This is especially useful when playing with a drummer who tends to push the power amp into distortion at high volumes.
Bassists who play large venues often choose a high-powered bass amp head matched with one or two large cabinets to deliver the needed sonic punch. The head and cab combination can range in price from $500 to over $10,000, depending on the level of power and sound quality desired.
Controls
The bass guitar head has a number of controls which control how the sound from the pickups is delivered to the speaker. Bass guitars often have a single volume knob for all pickups or two separate volumes for the bridge and neck pickups. Basses may also have a switch that blends or balances the two pickups. Basses may also have tone controls for bass, treble and sometimes mid frequencies. These controls are similar to those found on stereo systems and allow bassists to tweak the overall tone of their instrument.
A bass guitar is typically strung with nylon strings that are wound around steel rods. The rods are then wound with a magnetic metal to produce the electrical signals that turn the strings into vibrations. The vibrations are then amplified by the speaker and transferred to the air through the magnetic fields generated by the rods. Bass amplifiers are specially designed to amplify these low frequency vibrations and are able to reproduce them at high levels without distorting or overcompressing them.
In addition to the standard EQ controls found on all bass amplifiers, some have additional controls such as drive, compression and sub to add an extra dimension to their sound. These additional controls affect how the rest of the EQ settings respond and can give a bassist’s sound a more specific flavour depending on their playing style – for example metal players might want more distortion or funk players might prefer some compression.
Another common control is the string tree which is a small metal section found on the headstock of a bass guitar. When a bassist plays open strings, the two highest strings are ‘hung’ underneath this metal section which helps to provide some extra sustain and makes it easier to play the strings over the nut.
In more complex basses, the neck of a bass can be one solid piece of wood or it can be constructed by sandwiching together several layers of different types of wood. Many bass necks have a ‘cutaway’ which allows a player to reach higher frets. The neck of a bass can also have a’skunk strip’ which is a decorative strip of contrasting wood that covers the screw holes on the back of the body of a bass guitar.
Weight
Bassists, more than any other group of musicians, have been at the forefront of demand for lighter and more portable equipment. It is they who have been most keen to adopt every advancement in solid state technology that promises more power and flexibility with less weight than the hulking tubes that their forefathers relied on.
Most modern bass amps use transistors (also known as solid state) instead of vacuum tubes. Tube amplifiers require a lot of empty space inside to hold the large tubes and provide air circulation for cooling. They also need big transformers to provide current to the tubes and send the output from them to the speakers. All of that adds up to a lot of weight – a 50 watt tube amp can easily weigh 50 lbs or more.
Solid state amps are smaller and significantly lighter, and they do not need big transformers. This has been a boon for the bass player, as it has made it possible for them to have the tone of their dreams in a much smaller package.
A bass guitar head can be a standalone power amplifier or it can be part of a bass stack, which usually includes a speaker cabinet to deliver the full sound. Combo bass amps combine a head with a speaker in one unit, and they are a good option for beginners who don’t need the full power of a bass amplifier or for those who don’t want to deal with the extra hassle of transporting a separate amp head and speaker cabinet to every gig.
Increasing the mass of your bass guitar head can increase sustain. This can be done by adding a weight to the headstock, but it is best to experiment to find what works best for you. A quick test is to press the headstock against a door jamb. This will increase the resonance of the neck and reduce string drag, which subtracts energy from a vibrating string. Be careful to only add a small amount of mass to the headstock, though, as too much can negatively affect sustain by causing it to vibrate at different frequencies than necessary.