sentences:  The updated head featured JJ-branded preamp and driver tubes and "Winged C" 6550 power amp tubes, all tested and matched by Ruby Tubes in California, along with a thicker 1.6mm two-layer printed circuit board with through-hole plating and increased copper weight.In May, 2018, Yamaha Guitar Group acquired Ampeg from LOUD Audio.Ampeg continues to manufacture and sell Heritage Series and SVT Pro Series models of SVT.