SVT 3 Pro settings, as recommended by many: EQ to taste, other knobs and settings to taste as well. Dime the volume knob and use the Gain knob as master volume. Works nicely overall, get plenty of volume and good tone. Problem is that the amp has a "shhh" sound and occasional crackles. I figure that is a sign that I need to replace the tubes, since a similar problem in a Hartke head I had was greatly reduced when I replaced the tubes. Diagnosis anyone, before I send tubedepot about $55 of hard earned coin? Thanks!