The Ampeg SVT is a bass amplifier made by Ampeg. The SVT, which stands for Super Valve Technology, was designed by Bill Hughes and introduced in 1969. The SVT bass head produced 300 watts at a time when most amplifiers made less than 100. Throughout the years, the SVT has been through many design changes, but is still in production today.
There are three types of original SVT amps:
The first are the "blue line" SVTs. These are called that because of the engraved blue text and lines that surround the tone controls. Early 1969-70 "blue lines" used 6146B beam power vacuum tubes. The 6146B proved to be unstable in the high-voltage amp, and was switched to the more robust and reliable 6550 tube around mid-1970.
The second version of a vintage SVT is what many call the "black line" SVT. The lines and text are black instead of blue, and like the later run "blue lines" use 6550 power tubes instead of 6146Bs.
Later 1970s models have the same features as the "black line" SVTs except the lines around the tone controls have rounded corners and curve into the tone controls. They also came with 3-prong power cables, and no polarity switch. The SVT amps with 6146B tubes tend to put out a bit more watts of power as well as have a more pronounced grind in low mids that makes these amps desirable for some bass players.
The 6550A version of SVT amps tends to have a more rounder deeper bass sound, mainly due to the output transformer primary inductance with respect to plate resistance.The 6146 is much lower in transconductance and is less sensitive to drive signal, thus needs a bigger voltage swing to drive than a 6550. Another reason the 6146 amps have more growl than its 6550 counterpart is because the pre-amp is turned up a bit higher to achieve the equivalent power output swing, thus more grind from the pre.
In the early 1980s, Ampeg was bought by MTI in Japan, and the SVT resumed production there. Functionally identical, its primary cosmetic differences consisting of: white lettering on a black faceplate, black grill cloth, "elephant hide" or rougher textured tolex, and rack case-style spring-loaded handles, updated from the previous (and painful) rubber covered metal strap handles. Other notable differences of this era of SVT are found on the back panel, including a toggle switch for 2 or 4 ohm speaker impedance loads and a longer and thicker gauge 3-prong power cable.
Ampeg SVT-CL Specifications:
Preamp: Tube (2 x 12AX7)
Driver Tube(s): 1 x 12AX7, 2x 12AU7
Power Amp: Tube (6 x 6550)
RMS Power Output (2 Ohms): 300-Watts
RMS Power Output (4 Ohms): 300-Watts
Tone Controls: 3-Band
Mid Tone Control: 5-Position Selector
Ultra High/Low: Yes
Balanced Line Out: Yes
Preamp Out/Power Amp In: Yes
Slave Output: Yes
Dimensions (W x H x D inches): 24 x 11.5 x 13
Weight: 80 Pounds
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