Choosing A Bass Guitar Amplifier
Bass guitar is a complex instrument so getting the right tone can be challenging, but we are here to help...
Bass amps differ significantly from guitar amplifiers, in that they are attempting to reproduce significantly lower frequencies than a regular guitar amp and this typically requires more power and a different palette of tonal controls compared to the mid-range frequencies produced by electric guitars. Bass amplifiers are also generally expected to produce a cleaner signal than guitar amplifiers, without the overdrive/distortion and mid-range prominence that are often highly desirable in guitar amps.
Combo or Head and Cab?
The amplifier itself normally includes a preamp section for fine-tuning the sound with input gain and EQ controls (bass, mid-range, treble) and a power amp section that supplies the volume and power needed when connected to a speaker cabinet.
Combos incorporate the amplifier section and speaker cabinet into one enclosure, providing a portable, all-in one solution that is ideal for practice, rehearsals and gigs in small venues.
Combos are available in a variety of output / power ratings that normally correspond to the size of speaker they house from 8-inch to 15-inch speakers. The smaller the speaker the more lightweight and portable the combo will be, but this will nearly always mean lower output volume.
The down-side to using a combo amplifier is that you are committed to that speaker size, so if you want to add more low end to your 2 x 10" combo or more punch to a 1 x 15" combo you will need an external speaker. It also means carrying the whole enclosure around if you want to record some bass in the studio or run a direct out to the PA system in your rehearsal space.
Heads refer to units that house just the amplifier on it's own without a speaker enclosure attached, so called as they generally sit on top of a separate speaker cabinet that they are connected to.
Amp heads come in a great variety of sizes, weights and power ratings but as a general rule they get louder as size and weight increases, with the panel space that larger heads offer meaning they typically feature more professional features like detailed EQ, effect loop and channel switching.
The combination of a head and cab gives more flexibility and configuration options, as the cab can be swapped for different speaker sizes to offer different tones or to tailor the size of your rig to the gig. Because the head is separate from the speaker cabinet it can be used independently as a preamp for recording, or in rehearsal spaces and live music venues where speaker cabinets are already available.
Cabs is short-hand for cabinets, which are the speaker enclosures amplifiers are connected to in order to produce sound. The cab has an important influence on the tone of the bass, with large speakers such as 15-inch producing a deeper sound that accentuates the low strings.
Smaller speakers have a faster reaction time or transient response producing a snappier, more percussive sound that is important for the time keeping role of the bass as part of the rhythm section in a band. Although small speakers accentuate higher frequencies they can work in unison to push a large column of air when multiple speakers are housed in the same cab, so a 4 x 10" cab is a popular choice to cover both lows and highs.
Multiple cabs can be used with a single amplifier head and stacked to provide separation between the frequencies, for example a 2 x 10" cab with a 1 x 15" cab. This is an ideal set-up if space and weight allow and is particularly suited to the extended range of 5 and 6-string bass guitars.
Tube, Solid-State or Digital?
Tube amps are the most traditional design, using vacuum tubes or valves that produce a thick, warm sound still favoured by many bass players despite advances in amplifier technology. Tubes produce a characteristic distortion when overdriven called 'soft-clipping' that some bass players prefer, particularly in rock music. The Ampeg SVT is a classic example of an all-tube head, but their Portaflex range also features more compact, affordable tube models.
Solid-state components had largely replaced tubes in most consumer electronic products by the 1970s, and the clean sound of transistors is well suited to bass guitar amplifiers. Solid-state amps like Gallien-Krueger's RB Series are considerably lighter than their tube equivalents but still offer the high output required by professionals.
The introduction of digital / class-D bass amplifiers in the early 2000s has greatly reduced the size and weight requirements for producing heads of sufficient volume for performing gigs, even in large venues. Compact, lightweight heads such as Gallien-Krueger's MB Series are highly portable and can even fit in a guitar case or gig-bag for ultimate convenience. They are also ideal for fly-gigs and recording as their small footprint and direct output means they can be easily connected to a PA system, mixing desk or audio interface.