The Portaflex is a line of amplifiers for electric guitars and bass guitars created by Ampeg. Originally designed by Jess Oliver, the main characteristic of the Portaflex is that the head of the amplifier is stored inside the cabinet and flips over when being used. The Portaflex line has many different configurations.
SB-12
Ampeg manufactured the Portaflex SB-12 model amplifier from 1965-1971. This lightweight (67 pound) cabinet incorporated the flip-top design of other larger Portaflex amplifiers of the time. Although the SB-12 isn't as well known as the more powerful B-15, it is still highly sought after by musicians who use it mainly for studio recording.
The 'SB' in SB-12 stood for string bass; the '12' indicates the diameter of the speaker in inches. It contained a single-channel, 25-watt tube amplifier and a single Jensen speaker. Unlike bulk of the Portaflex line of bass amplifiers, the SB-12 was designed as a universal amplifier. It incorporated two separate inputs, one labeled "Bass" and the other "Instruments".