I recently purchased an ampeg ba-115 and I have a slight problem. Sometimes when I play through the amp, some of the notes sound out of tune by a half step or so. The guitar is definitely in tune, and I played it on other amps without this problem. This leads me to believe that the amp is the problem. Also, if this helps (especially if you are familiar w/ the amp), it seems to be worse with the style selector set on "1" (the fattest and best-sounding one) and the problem is very rare on style "5." Please let me know what is going on!