Ampeg SB-12 Portaflex Model Fliptop Bass Amplifier (1966), made in Linden NJ, serial # 025898, blue checked Tolex finish.
Ampeg's 1960s SB-12 was a slightly simplified, lower-powered line-up companion to the iconic B-15N, taking the place of the earlier Portaflex B-12N and B-12NL. This particular example is one of the last of Ampeg's "blue-checked Tolex era" from 1967, which gave way to a less distinctive black covering the next year.
At the time the SB-12 was primarily marketed as a companion amplifier to the upright Baby Bass. Ampeg legend holds that "SB" stood for "string bass" and was Everett Hull and Jess Oliver's preferred design for upright bass once the B-15s became more deliberately marketed for the electric bass guitar. Earlier catalogs proclaim the B-12 models to be for "upright bass primarily" and the B-15 models to be for electric or "upright bass if a deeper tone is desired".
Featuring a simplified single channel design, the SB-12's front panel still sports the familiar dedicated instrument and bass inputs alongside master volume, treble and bass controls. Two 7868 power tubes in push-pull yield approx. 25 watts of power into a single 12" speaker. This iteration of the model also had the fairly clever idea of connecting the speaker through the cabinet latches, eliminating the need for a dedicated cable. This particular example also has the chassis mounted directly to the lid, forfeiting the 'shockmount' tray commonly seen on Fliptops; this appears to be the way this amp left Ampeg, as the schematic and wires appear unaltered. While less powerful than the B-15 this is still a lovely lower-volume bass amp, quite suitable for recording purposes with a versatile sound and the deep round response Portaflex Ampegs are famous for.
Height is 27 3/4 in. (70.5 cm.), 17 5/8 in. (44.8 cm.) width, and 12 5/8 in. (32.1 cm.) deep.
Cosmetically, this amp has seen some wear and tear over the years but overall is in fairly decent shape considering the less durable covering of this era. The signature blue-checked Tolex is overall intact, save for a few minor scuffs here and there. The chassis is clean overall with all the original knobs present. There is some light corrosion to the chrome but most of the decorative stenciling is still nicely intact. The grille cloth is clean and nicely intact with no notable signs of tearing or fraying and both the illuminated acrylic plate and metal logo are present as well. The handle is a newer correct replacement.
Electrically, the amp is nicely original overall. Although no legible markings remain, the speaker appears to be the original square-magnet CTS, which both tests and sounds great. The power and output transformers are both original and bear the codes 682-543, 682-539, dating them to the 43rd and the 39th week of 1965, respectively. Visible pot codes all date to 1966. The only modification is that the amp has been converted to use a solid-state rectifier, much like the short-lived Ampeg B15NB. Otherwise, has seen our typical maintenance and servicing, including a grounded 3-prong power cord, some light speaker and baffle repair, replacement of electrolytic capacitors, replacement of any out-of-spec components, cleaning of all sockets, pots and jacks and power tubes biased to spec.
This SB-12 sounds great, making for a fine lower volume bass amp (set at "4.5" or below) offering a nice warm well-rounded sound. It can also double as a surprisingly rip-roaring guitar amp when cranked; in many ways a perfect home or small studio 2-in-1 recording amplifier. Overall Very Good Condition.
