Leo Fender's development of the electric bass was as much a musical revolution as the Esquire/Tele electric guitar he also brought to life. Suddenly, bassists weren't stuck behind a cumbersome, unwieldy wooden box. The sleek profile, comfortable neck and lighter weight of the original 1951 Precision made it possible for the 4-piece rock group to displace the big bands of the previous generation.
Unfortunately, accurate reproduction of the P's intense low notes would take a few more years to develop. The original '52 Fender Bassman, the amp intended to match the first-generation Precision, was a combo amp with 26 watts (8Ω) into a single 15" speaker. These days, that would be OK for a practice amp, or a coffeehouse gig with an acoustic guitar, but not for a full size band.
After brands like Marshall came to prominence, the amp war started to heat up. Unfortunately, that's also when chiropractors and physical therapists started raking in the bucks. Those puppies were (and remain) daunting challenges to anyone without a road crew.
However, things have now come back down from the monolithic stacks that kicked in stadium and arena doors of the late '60s and early '70s. The combo amp has re-asserted itself in the bass players' arsenal, and its' cousin the mini-stack is standing right alongside. Here are some notable examples.
Ampeg started out specializing in bass amplification. Their first product (in the 1940s) was a pickup for string basses called an "amplified peg", hence the name. Since that time, they've been a favorite of bass players worldwide. One of their current offerings is the Micro series. The Micro VR head is a MOSFET (solid state) amp putting out 200 watts into 4 ohms RMS; expect prices in the low-to-mid-$300s. There's a matching cabinet with two 10" Eminence speakers. It's ideal for small to medium club or studio settings, with a punchy, full sound. Likewise, the cab is priced in the same low-$300 range.
For decades, the Ampeg Portaflex was the go-to combo amp in the studio. Now, there's the PF-350, a Class D (switching power supply) amp small enough to fit in a backpack, with 350 watts into 4 ohms RMS. Most websites will accommodate prices around $300. The PF-350 will fit neatly on top of the current Portaflex PF-115HE cabinet, which augments the 15" speaker with a compression tweeter and high-end level control. The compression driver is a welcome alternative to the usual piezo tweeter, which can often sound harsh and scratchy. Prices for the cabinet are mostly in the low-to-mid-$400's.
TC Electronic has some chips in the bass micro amp game, also. The BH and RH series are for portable power, with a small footprint. Aside from a minor product recall with the BH 250 (some of the mounting nuts inside the unit weren't properly secured), they haven't had any complaints form their legions of fans. There's also the BG250, a combo Class D amp with a 15" woofer and a high frequency driver, as well as on-board effects which can be downloaded from the TC website. Recent price drops (look for prices in the mid-$300 US range) make this an attractive option for the gigging bassist.
Of course, no one can dispute the impact that Gallien-Krueger has had on the bass world. They were focused on solid-state design from the start. Their current MB series (amp/cab and combo units) keep an eye on the scale and the price tag, while putting out 100 watts (8 ohms) and better. One can spend less than $500 US retail and walk out with a well-voiced, powerful set-up that covers everything but the largest venues.
Although there are several other brands that fit in this niche (Peavey, Hartke and Roland among them), let's close here by bringing things full circle. Fender has kept things going for its' bass faithful, with their Rumble combo amp series. The combos have stepped up considerably from their humble beginnings. How about the Rumble 350, with two 10-inch bass drivers (and a high-frequency transducer with cut-off switch) in a ported enclosure pushed by 350 solid-state watts (4 ohms)? It also features a 4-band active EQ, 6 dB input pad for active pickups, built-in compressor and an XLR direct out jack. Not bad for a street price of about $500 US.
That's just a snapshot of some currently available amps, that can handle almost anything you need short of the O2 Arena or Madison Square Garden. The gigging bassist now has greater choices than ever, and less weight to carry around than before.