sentences:  The second version of a vintage SVT is what is called the "black line" SVT, earning its name from the black (rather than blue) faceplate screen printing.Like the later-revision "blue lines" models, the "black line" SVTs utilize 6550 power vacuum 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.