Groove Tubes GT-ECC83-S. Note: All tube sales are final. Groove Tube's highest-gain preamp tube, this tube has a huge amount of gain, with terrific output that makes it a great choice for driving modern, complex high-gain circuits. It has a tight, strong and relatively bright tone that can really liven up a weak or tired old vintage amp or a new amp with stock tubes. • MFSKU 5550112391 • UPC 736021123915