Lynn,
I am having some real issues with the A-string on our upright bass. Here is our current set-up: Shen SB150, Helicore G & D, Spirocore A, and Obligato E. Using a Schertler Stat-B pick-up with an Euphonic Audio Doubler amp and Wizzy 12 speaker.
We get a real thumpy attack with the A...