Guitar 101: What Is a Bass Amplifier?

A bass amplifier is an electronic device that makes the sounds of a bass (or other low-pitched) instrument audible to audiences. Most bass amps are designed for electric basses: the bass strings produce audio vibrations, the vibrations are converted to electrical signals by the bass’s pickups, and the amplifier process those signals, sending them back out into the world as audio from the amp’s speaker.

Bass amplifiers convert an electric signal into an audio wave over the course of four internal sections:

• The preamplifier (a.k.a a preamp or pre)
• Tone controls
• The power amplifier
• The speaker

The differences between these four components are what distinguish one model of bass amp from another.

• Bass amps differ from other electronic amplifiers (like those for guitar) due to the physical requirements for amplifying low-end frequencies. As a general rule, the larger and heavier the amplifier is, the more able it will be to produce satisfying bass tones.
• To contextualize this, think of a home stereo system. Most multi-speaker systems feature relatively small left, right, and center speakers. Some “surround” speakers even fit on bookshelves. But the subwoofer, which produces bass, is large and heavy, and usually needs to reside on the floor.
• The same physical requirements that make home subwoofers large and heavy also govern amps for electric bass. While some of the most famous electric guitar recordings were made on tiny amplifiers with 10-inch speakers, bass amps tend to be quite large, with speakers starting around 15 inches and increasing from there.

Unlike most guitar amplifiers, the majority of bass amplifiers are solid-state. They don’t use vacuum tubes (or valves) in their preamp and power amp sections. This wasn’t always the case, however. Shortly on the heels of inventing the groundbreaking Precision Bass, the Fender Musical Instrument Company created the Bassman amplifier, a 50 watt tube amp. Early rock n’ rollers embraced it, but the Bassman was also popular with guitarists. In fact, it became the basis for Marshall guitar amplifiers built in England. (Fender employees are said to refer to a Marshall amp as an HMB—”Her Majesty’s Bassman.”)

Among the most famous tube amps for bass are the:

• Fender Bassman Pro 100T
• Ampeg SVT-CL series
• Orange Amplifiers AD series

But tube amps have their disadvantages. For one thing, tube systems make amps heavier, and bass amps were already heavy to begin with—much more so than a typical guitar amp. Tubes are also fragile (they’re made of glass) and simply weren’t the best fit with big, bulky bass amps. What’s more tubes were sought after by guitarists to intentionally color their tone by adding a mild form of distortion. This helped soften the guitar’s sometimes piercing high frequencies. Bassists, by contrast, had less use for this tube-based distortion. This led them to solid state amplifiers.

Solid-state amps use transistors to amplify sound. Compared to glass vacuum tubes, transistors are lighter, less expensive, less fragile, and easier to maintain. Guitarists nonetheless often resist transistor-based amps because they tend to accentuate piercing high tones without the mellow distortion that tubes provide.

Bassists don’t have to worry about piercing high tones and they rarely seek out distortion. Therefore the advantages of tube amplification didn’t apply to them as much, and over the course of the 1960s and 1970s, many bassists switched to solid-state amps.

Among the most well-regarded solid-state models are the:

• Markbass CMD series
• Gallien-Krueger MB112 combo amp
• Ampeg SVT-7PRO Head
• Aguilar AG 700
• Fender Rumble 40 and Rumble 500 (lower-priced options)
• Peavey Max 115 (another budget-friendly option)

Some bass players get trapped in the tube vs. solid-state conundrum, but fortunately for them, another option exists: a hybrid amp. These typically have tube preamps (which, compared to power tubes, are lighter and require less maintenance) and solid state power amps. For bassists who want a little natural grit in their tone, a hybrid amp can be a “best of both worlds” solution.

Hybrid bass amps include the:

• Fender Bassman 800 Hybrid
• Gallien-Krueger Fusion 550
• Aguilar DB 751
• Hartke HA3500C

A bass amp is a big investment, but it’s one that’s shaped by personal taste. The best bass amp for one person’s style of playing may not be ideal for someone else’s. So while keeping in mind that bass tone is subjective, here are some things to look for:

1. 1. EQ options. Any bass amp you purchase can provide a wide range of tonal possibilities via its EQ section. The basic amps will include a 3-band EQ, which is typically denoted through knobs marked Low, Mid, and High. But if you have the option to get an amp with a 4-band EQ or more (such as an amp with a graphic EQ), it may be worth the extra money. Shaping your unique tone can help you stand out among the competition.
2. 2. Think about where you’ll be playing. If you aspire to be a regular gigging bassist, you’re going to be hauling around an amp quite a bit. (A lot of nightclubs have their in-house bass amp, but there’s no guarantee you’ll like what they have on offer.) So for players lugging gear, consider a bass combo amp, which combines the actual amplifier and speaker in one single package. If you’ll mostly be in a studio, maybe a heavier tube amp (with a separate cabinet) will better suit your tonal needs.
3. 3. Will you really use the tube sound? Tube amps are great when they make practical sense. But their weight and cost can be drawbacks. Consider whether your personal tone requires that tube saturation. Or perhaps you can achieve that effect using stompbox pedals or a tone shaping plugin on your recording software. But if you know you need that tube sound to achieve great tone, don’t hold back. Above all you want to select an amp that you’ll be thrilled with for years to come.

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