Ampeg B-15N Portaflex Model Large Tube Bass Amplifier (1963), made in Linden NJ, blue checked Tolex finish.
Overall this is a very nicely preserved example of the all-time classic recording bass amp, Ampeg's B-15N. Conceived by Jess Oliver in 1958, the iconic 'flip-top' design has been for decades since the preferred in-house bass amplifier for the great majority of professional studios, and was a lower-volume gig standard from its early days as a union-provided amp on the Manhattan bass club scene.
The 'flip-top' design was partly inspired by contemporary sewing machines, allowing the amp to effectively be stored inside of itself, making it highly practical for transport. Another innovation was the double-baffle cabinet design, which places the speaker between two baffles, one outer and one inner that was fixed to the cabinet, and to which the speaker would be mounted to. The inner baffle featured a number of ports, effectively allowing the rear and the front waves of the speaker to meet perfectly in-phase.
The B-15 saw a number of revisions through the first half of the 60s. This particular amp appears to be a rarely seen transitional specimen, still utilizing a 5U4G/5U4GB tube rectifier and octal speaker connectors of the initial design, alongside their new signature blue checked Tolex covering, but still prior to the switch to a solid-state rectifier in the 'NB' revision; this amp lies somewhere between the initial N and NB! Because the 5U4 drops about 50 to 55 volts, these earlier models have a uniquely warm and more compressed, "sag-heavy" characteristic coveted by James Jamerson fans!
The amp features two channels, each with its own volume, treble and bass controls, guitar and bass inputs for channel one and an instrument input for channel two. The push-pull 6L6-driven power section puts out roughly 25 watts into a single 15" speaker.
From James Jamerson to John Paul Jones, to even Jimi Hendrix, who was known for plugging into a pair on occasion, these amps have arguably hosted some of the most influential musicians in modern times. Any studio claiming to embrace "Vintage sound' needs at least one of these amplifiers in their sonic arsenal.
Height is 29 in. (73.7 cm.), 21 in. (53.3 cm.) width, and 13 3/4 in. (34.9 cm.) deep.
Externally, this amp is very well-preserved. The signature "Blue Check" Tolex is in fabulous shape with only some VERY minor wear mostly around corners and edges. There are a couple lighter scuffs to the tops of the transformers and tube cage from decades of the amp being flipped and stowed in the cabinet. The grille cloths is equally in great shape, with no notable signs of tears or fraying. The original Ampeg logo from the upper front of the cabinet is present as well. The chassis is beautifully clean overall, showing only light wear overall and the amp even retains the original earlier plastic handle!
Internally, this amp remains mostly original. Although no serial number visible, components date the amp to 1963. The speaker appears to be the original Ampeg-branded Jensen C15N. The speaker retains its original cone and sounds great. Visible pot codes date to early-mid '63. as is very common with Portaflex models the power transformer is a newer correct replacement repro; the output transformer is original. The amp has otherwise seen our typical servicing and maintenance, including replacement of all electrolytic capacitors, adding a grounded 3-prong power cord, cleaning of all sockets, pots and jacks and biased to spec.
This is a lovely example overall; a true classic amp and perennial studio staple that always sounds as "classic: as it gets. Excellent Condition.
