Know Your Ampeg Bass Amps

Ampeg bass amps are so universally revered, it’s hard to imagine a time when they weren’t synonymous with electric bass amplifiers. But what started from a modest idea — literally, an “amplified peg” that would install into an upright bass — in Everett Hull’s modest shop in Midtown Manhattan in the 1930s, has become a towering name in the world of bass amplification.

The three Brainworx-developed Ampeg bass amp plug-ins available exclusively for UAD hardware and UA interfaces are the bedrock of the thundering Ampeg legacy and nearly every bass amp that came afterward. Each of these amps remain a staple in studios and stages around the world — with the UAD Ampeg plug-ins delivering spot-on results — and they each give you a different flavor of classic Ampeg bass tone.

Here, we decode what makes each of these iconic tone machines tick, and delve into the different components that contribute to each amp’s distinct, glorious rumble.

1960. Ampeg B-15

Forever associated with Motown bass legend James Jamerson, as well as Stax low-end kingpin Donald “Duck” Dunn, the Ampeg B-15 Portaflex (short for “portable reflex cabinet”) features a distinctive “flip-top” 30-watt all-tube head, complete with classic two-band Baxandall EQ, that could live inside the double-baffled 1x15 cabinet (typically a Jensen P15N speaker) while travelling, and flip upright to sit atop the cabinet during recording or gigs.

With its clever “tube cage,” the amp’s pair of 6L6 power tubes and three 6SL7 preamp tubes are kept out of harm’s way while the head was inside the cabinet. More importantly, the B15 sounds warm, round, and resonant — as suitable for jazz and soul players as it was for the growing army of rock and garage band aficionados.

Ampeg’s Heritage Series B-15N added a few key twists to this legendary design, notably the introduction of two separate preamp sections: one modeled after the spongier, quicker-to-distort 1964 preamp, a 25-watt cathode-based circuit; and the other the slightly cleaner and midrange-forward 1966 version, built around a 30-watt, fixed bias design. What’s more, each preamp’s selectable bias mode can be used with either preamp, allowing for even more subtle tone shaping.

The B-15N boasts a powerful twin-6L6 power section, three 12AX7 preamps, and a 5AR4 tube rectifier, along with an Eminence 15” speaker. The B-15N’s distinctive “double-baffle” porting is especially worthy of note, as it’s a revolutionary porting system that originated in 1960, and would be used for almost two decades of the combo’s stunning initial run, and is still used in Ampeg’s more recent Heritage B-15N reissues.

Listen to the Ampeg B-15N Bass Amplifier plug-in for UAD-2 and UA interfaces and dig how it perfectly emulates the classic thump of this coveted amp.

1969. Ampeg SVT-VR

As guitar amplifiers were getting bigger and louder toward the end of the ’60s, Ampeg — best known for compact amps with lots of clean headroom — jumped into the fray, debuting a massive new amp at the 1969 NAMM show, designed by Bill Hughes, that would become their best recognized, flagship bass amp for years to come: the 85lb, 300-watt RMS behemoth known as the Super Vacuum Tube, or SVT, which was designed to be paired with — not one — but two gigantic 8x10 Ampeg cabinets. Indeed, the SVT’s unprecedented power output raised concerns at the time about Ampeg’s legal liability, leading the company to ship SVTs with an ominous warning label: “This amp is capable of delivering sound pressure levels that may cause permanent hearing damage.”

As Ampeg’s Roger Cox has said of the beast, “We were going to build the biggest, nastiest bass amplifier the world had ever seen.” Ironically, though it’s now recognized as the essential big-venue bass amp, and was certainly designed as a bass amp, it wasn’t until 1974 that Ampeg officially listed the SVT specifically as a “bass amplifier.” Indeed, the Rolling Stones arguably put the SVT on the map in 1969 by taking a fleet of them on the road — paired with a variety of cabinets, including 4x12s and 2x15s — as both guitar and bass rigs for their world tour of that year.

Thus, what began as a slightly eccentric, even dangerous deviation from Ampeg’s more sober product line became the signature workhorse of the Ampeg brand, with a sound — fleshy, full of midrange growl and deep, resonant lows — that fills out rock and reggae mixes like nothing else.

The original SVTs from the late ’60s and ’70s were two-channel affairs, using a grand total of fourteen tubes, requiring a filament transistor and a cooling fan to keep the heat at manageable levels. These included six 6550 power tubes along with 12DW7 preamp tubes (eventually changed to 12AX7s). The SVT-VR (for “Vintage Reissue) retains most of the 70s classic’s feature set and styling — including two-channel operation, both bright and normal inputs, “Ultra Hi,” “Ultra Lo” and, for Channel 1, a “Bass Cut” switch and a midrange frequency select switch that allows users to craft their midrange timbre around either 220Hz, 800Hz or 3k center frequency. That combination of sheer power, timbral richness, and tonal control is why players from Roger Waters and Bootsy Collins to Tony Levin and Chris Squire leaned on the classic SVT live and in the studio.

Hear how the Ampeg SVT-VR Bass Amplifier plug-in for UAD-2 and UA interfaces not only captures the beastly roar and rock solid tone of the most popular bass amp ever, it also expands on it with various cabinet choices.

The ’80s & Beyond. Ampeg SVT-3 Pro

With its single channel, hybrid solid-state power amp and tube preamp sections, rackmount design, and onboard 9-band graphic EQ, the SVT-3 Pro, designed by Dave Pepmiller, is an entirely different kind of SVT. Still, with up to 450 watts of RMS power output and the same type of low and high boosts that make the SVT-VR such a workhorse, it offers much the same sonic boom — and arguably a tighter sound, more conducive to soloing, modern rock and metal, and brighter, funkier parts — at less than a third of the overall weight and about half the size of the all-tube SVT.

Jettisoning one channel of the older SVT allowed the SVT-3 Pro (inspired and designed in the mold of the earlier SVT-II) to add a footswitchable graphic EQ, along with an expanded 5-position midrange control — with a choice of center frequencies at 220Hz, 450Hz, 800Hz, 1.6kHz, and 3kHz — for even more surgical timbral crafting.

Perhaps the SVT-3 Pro’s two coolest features, though, are the Gain and the Tube Gain controls. Gain varies the amount of signal driving the preamp, allowing for effortless introduction of rich harmonic saturation from the amp’s phalanx of four 12AX7 preamp tubes. Tube Gain, meanwhile, varies the high voltage to the preamp tubes, for a more compressed and thicker sound at low levels, to an explosive, highly dynamic tone at the upper end — especially if you crank the amp’s power section at the same time.

The Tube Gain control is super useful for virtually any genre, really letting those nuances of your playing shine, but it’s surely not for the faint of heart. Which is perhaps why guys like Metallica’s Robert Trujillo and Primus’ Les Claypool swear by the SVT-3 PRO.

Check out how the Ampeg SVT-3 PRO Bass Amplifier plug-in emulates this modern rackmount classic to a “T,” elegantly modeling the wide array of tone sculpting controls, as well as its hybrid power section.