Wednesday, September 28, 2016

American Muscle: The Ampeg SVT

In the late 60s, England was clearly in the driver's seat of the high-powered tube amplifier game. Fender designs had topped out with the 100-watt Dual Showman, while bands like Cream and The Who were filling arenas with 200-watt heads by Marshall and Hiwatt, and walls of 4x12" cabinets stacked behind them. The Rolling Stones, however, weren't too keen on the British rock sound at the time, after their initial endorsement deal with Vox expired, and preferred the "American" sound of Fender amps like the Twin Reverb and Showman. When they arrived in America for their massive 1969 world tour, one thing was certain: they needed power behind them.

The original Ampeg HQ, Linden, NJ

Ampeg built it's name in the 1960s with their flip-top Portaflex bass combos, becoming an industry standard for bass amplification with the B-15 used in studio and live by Motown's James Jamerson, Stax' Donald "Duck" Dunn, and countless others.  Their ReverbRocket guitar combo amps were also the first to include built-in reverb, beating Fender to the punch by about two years. Along with the Jet and Gemini amp models, Ampeg competed neck-in-neck with Fender in the early 60s, but despite these great products, the original owner of Ampeg, Everett Hull, had a strong aversion to rock'n'roll music and treated it as a passing fad. The company never evolved the way Fender did, and by 1968 was sold to Unimusic, where Dan Armstrong and Bill Hughes would push Ampeg into a new generation, with some bold new designs.

The incredibly innovative and still hip Ampeg B-15N Portaflex combo

Meanwhile, the Stones were rehearsing in Hollywood, getting ready for their biggest tour yet, and their entire backline of Fender amps had been fried by the change in voltage from Europe to the US. Their road manager, Ian Stewart, reached out to Rich Mandella of Ampeg, who had a regional office nearby, and he came to the rescue with several prototypes of a brand new design, the only units in existence at the time.

An original "blue line" SVT head

The SVT, or Super Valve Technology amplifier, was Ampeg's answer to the high-powered English amps of the day, yet delivering a unique tone of it's own. Featuring 14 tubes, delivering 300 watts RMS, and weighing 85 pounds (just the head alone), the SVT was unlike anything before it, and changed the game for everything after. Originally using six 6146B power tubes, the heads required two cabinets to function properly, until proper speakers were designed to handle the amp's power. The amps offered the cryptic warning label on the back, “This amp is capable of delivering sound pressure levels that may cause permanent hearing damage”.

Original SVT doublestack; Hurts just to look at.

As Keith Richards, Mick Taylor, and Bill Wyman all began using these new amps, the volume grew louder and louder... and Keith loved it. The sound was thick, muscular, and powerful, with both guitar and bass. The Stones kept the prototypes for their entire tour, including the infamous Altamont festival, and Rich Mandella accompanied them as official Ampeg babysitter along with a team of techs to prevent the new designs from meltdown. These original SVTs can be heard on the Stone's fantastic live album Get Yer Ya-Ya's Out, and also in the Gimme Shelter concert film

The Stones on tour with Ampeg SVTs behind them

Keith taking a break in front of his Ampegs

After this beta-testing period with the Stones concluded, the SVT went into production, first with the original 6146B power tubes plus an extra delay relay tube (which was quickly omitted, only 50 or so amps made with this), and by mid-'70, switched to the more stable 6550A power tube. Although still technically requiring a pair of cabinets for full power, most were paired with a single 8x10" cabinet designed specifically for bass, remaining a classic partnership for decades. The square-back cabinets featured custom-designed speakers by Bob Gault, originally manufactured by CTS, later by his offshoot Eminence in 1972 (An upcoming speaker post will explain this in greater detail). The combined surface area of eight 10" speakers, along with the faster reaction time of smaller drivers emphasizing the attack and upper harmonics of the tone made the 10s a much better option than larger 15- or 18-inch speaker options.

The SVT's popularity among the Stones led to the development of the V4 (100w head), V2 (60w head), VT-22 (2x12" 100w combo), and VT-40 (4x10" 60w combo) guitar amps, all featuring the same preamp circuit with a power section based around 7027A tubes, and available with a 6550A upgrade kit for more power as well. There was also the V4B 100-watt bass head, B-25 55-watt 2x15" tube stack (although more closely related to the B-15 combo in circuit design), the BT solid-state series, and the very rare SBT solid-state preamp with a pair of self-powered 2x15" Altec-Lansing cabinets delivering 240 watts RMS. Later on, the V9 amplifier and even larger 9x10" cab were introduced for guitar, featuring the same 300-watt power section as the SVT (the amps would even share the same chassis, labeled SVT/V9 on the back panel), but with a similar preamp and tone circuit as the V4, and reverb. 

The VT-22 and VT-40 combos became favorites of the Stones in the studio for some of the best recordings of their career, and when they embarked on their even bigger 1972 world tour, exclusively featured an entire backline of Ampeg, particularly SVTs and V4s (Keith was also playing the Ampeg Dan Armstrong see-thru guitar quite a bit at this time). The entire amp lineup became very popular throughout the 70s, and is still favored by some for it's thick, muscular midrange tone, like Josh Homme of Queens of the Stone Age, who uses a wall of VT-40s on tour, and others in the studio. Early 70's models were non-master volume designs, with independent volume controls and reverb, while beginning in 1976, models featured a switchable distortion circuit as well as reverb.

Keith Richards playing a Les Paul through an Ampeg VT-22 while Mick Jagger observes,
at Sunset Sound in Los Angeles finishing up Exile On Main Street

Keith's Ampegs doubled as a wet bar

An early 70s Ampeg ad featuring the Stones

An early 70's V4 head (top) with separate volumes,
and a later 70's V4 (bottom) with distortion circuit

Slight variations on the front panel design of the SVT include the change from "blue lines" to "black lines" around the knobs, coinciding with the company's purchase by Magnavox in 1971, shortly after the switch to 6550A power tubes (blue line SVTs with factory-installed 6550As are considered the rarest models, but originals that haven't been converted from 6146Bs are growing scarcer, as most users have this procedure performed by an amp tech). Circuit-wise, there were no major changes at this point. Later in the 70s, the black lines became curved, along with the change to more modern three-prong AC cables and loss of the polarity switch. In 1980, Ampeg was purchased by MTI, a Japanese company, and the look was changed to all-black with white lettering; still the same basic circuit, and great sounding amps. MTI declared bankruptcy and was acquired by St. Louis Music in 1986, bringing the Ampeg name back to America. A "Drive" control was eventually added to the circuit in 1992, the first major design change in years, enabling preamp tube saturation at lower volumes.

An original "blue-line" SVT head on top of a late 70s "curved line" head
Great example of a 1974 Magnavox-era "Black line" SVT

An 80s MTI SVT atop a monstrous V9 cabinet (left),
while a V4 head sits atop a smaller cab, possibly 2x15" (right),
with an Ampeg Dan Armstrong guitar resting in front of it.

Ironically, it was an SVT bass head cranked to the hilt that Elliot Randall used to record the famous guitar solo on Steely Dan's "Reelin' in the years"; for a band that spared no expense in the studio, it was the only amp available that day, and "worked a storm" according to Randall, as the thick tone along with his incredible performance became the signature of the tune. The influence of the SVT can also be found in many rare Dumble amps, particularly the Dumbleland Special and Steel String Singer power sections; Stevie Ray Vaughan's Dumble was once crudely described as a Twin Reverb preamp with an SVT output section, although this is a gross oversimplification of a great design.

The SVT amp & cabinet has been the industry standard since it's inception, used by countless bassists across all genres, from hard rock and metal to funk and indie, even some blues and jazz players (although the B-15 is still very popular for those styles). Robert Trujillo of Metallica, Cliff Williams of AC/DC, Sting, Tony Levin, and Juan Alderete are just a few famous SVT users over the amp's history. Ampeg ownership has changed hands several times, but the popularity of the SVT has never showed any signs of decline, with the original design still in production today as the Vintage Reissue (VR) model, along with several variations over the decades to meet the needs of the day, such as master volume circuits, the SVT Pro series with rackmountable chassis, and the SVP preamp. It's a testament to great design and a forward-thinking business model that wanted to be the best and loudest in the world.

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  1. Not to be picayune but the VT-40 is a 60-watt amp, not a 50-watt amp. And the V4, VT-22, V2, VT-40 amps are all based on the 7027a power tube. This is important to point out because that tube is part of their unique tone and powerful volume.

  2. I've been using them almost exclusively since 1977. Started out with an original 6550 blueline which I stupidly sold in 1995 with two cabs and went to two 70's curved line heads with early square back cabs. Love the tone and the fact that it's almost impossible to get to the breakup point in clubs. I also use a B-15S and have owned other B-15's over the years, Ampeg has The Tone.

  3. "We were aware of Peter Traynor's work in Canada" (from memory, not an exact quote)
    Traynor's big bass amp had six ten-inch speakers, and in those days big bass amps did not have ten-inch bass speakers. I think that the Traynor was about the biggest at that time.

    I just say that because we were big Traynor fans in those days and if the Traynor design influenced the SVT (I think it had to) I'd love for it to be in the record.

    Or if this is all baloney, then forget it.

  4. Hi Am a Belgian dinosaurus tube tech and to me Classic and Heritage SVT 410 HLF are the best bass cabs I ever played and worked with they are so sweet and deep , no SVT fridge 810 can match the deep warm bassreflex sound of the HLF ; but I must admit my custom Faylon pro 200 Belgian Vintage production amp is absolutely tops and beats the Old V4b that I own , both in dynamic power and in tone versatility . anyway Ampeg is a standard !

    1. Bonjour. Avez-vous une expérience des ampeg svt II pro ? Car j'ai lu beaucoup de choses sur la modification de ces amplificateurs pour une meilleure fiabilité. Merci

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