Following the introduction of Leo Fender’s groundbreaking electric bass came the need to amplify the sound it produced. It was Ampeg who really focused their efforts to make a useable amp for the working bassist. This is perhaps due to the fact that Ampeg was owned and run by bass players. They produced a product that would define the sound of the electric bass.
Ampeg has been in business since 1949, when they were founded by Everett Hull, two years before Leo Fender’s electric bass went in production. Hull, himself a gigging upright bassist, had developed a pickup system for double bass in 1946. This attached to the end-pin, or peg, inside the bass itself. His wife Gertrude named the new bass microphone the Ampeg – short for ‘amplified peg’. The Hulls moved to Manhattan and changed the company’s name to the Ampeg Bassamp Company. Hull spent the first few years developing the Ampeg string bass pickup and producing the first amplifiers to pair with it.
A young electrician and gigging bassist named Jess Oliver took a visit to Ampeg in 1956 to buy one of Hull’s pickups. Hull was so impressed that Oliver had deftly installed the pickup on the spot that he offer him a job there and then. Soon after Oliver quit his job as an electrician and began to work for Ampeg, with Hull even paying for him to go to night classes to study amplifier design.
Oliver was dissatisfied with the amplification systems then available, including Ampeg’s own closed back designs. The bass response was still poor and reliability a serious issue. Oliver set about designing a new double baffle cabinet that would allow the bass frequencies to be better reproduced. While all amps to this point had been combos, several companies had experimented with separating the fragile electrics and valves from the cabinet. Oliver took this idea and having seen the Singer sewing machine’s rotating mechanism, added a flippable lid for the amp with the ‘head’ section attached.
The first Portaflex – a shortening of ‘portable reflex baffle system’ – was the 25-watt B-15, which appeared in 1960. It was quickly nicknamed the ‘flip-top’. It featured a many innovations, such as a single heavy duty 15” Jensen speaker, a closed back cabinet with tuned porting giving excellent bass response, and a new reflex design dampening the speaker and reducing speaker malfunctions. In addition, the B-15’s detachable head gave better cooling for the valves, plus reduced vibration, and was shock mounted, protecting the delicate electronics, thus making the whole unit much more reliable. Its success was instant and Ampeg quickly rolled out an entire line of Portaflex amplifiers including the B-12N with a smaller 12” speaker, the B-12X featuring vibrato and echo, and an electronically updated bass amp, the B-15N. By 1964 almost half of the amps sold by Ampeg were from the Portaflex line.
The B-15N became the bass amplifier of choice for just about every session and studio musician from 1960 onwards. Charles Mingus, James Jamerson and Bob Babbitt are just a few of the names who used the B-15N on countless thousands of records between 1960 and 1990. It was finally discontinued in the early 80s.
Ampeg released a reissue of the B-15N in 1997, named the B-15R. It was a dead ringer for the original B-15N, featuring the familiar blue check vinyl covering, light-up logo, and retro knobs and switches, although it had an infinite baffle design rather than the double baffle system of the original B-15N, which changed the sound significantly. It was also rated at a full 100 watts as opposed to the original’s 25.
In 2011 Ampeg released a limited edition ‘Heritage’ version of the B-15N. Jess Oliver was a technical adviser on this reissue and was keen that it was as close as possible to the original units in tone and design. It used the traditional double baffle design, period correct electronics including military NOS 6SL7 valves, and a custom designed Eminence 15” speaker. Oliver did add a few tweaks that he felt were improvements over the original design, including a choke to enhance the efficiency of the power section, and separate circuits for either a 64 bias (B-15NC) or 66 bias (B-15NF), widely considered the most sought-after incarnations of the B-15N.
Vintage B-15Ns are now desirable for their groundbreaking tone and retro appeal, and as a result they command a high price on the used market.