After spending ages deciding on a cab, I saw an Ashdown MAG 115 this morning for less the I expected so I got it. I have a Hartke Mosfet 3500 (350watt 4 ohm, 240watt 8ohm) which I haven't had a cab for since buying, I got the cab home and was playing fine, sounded great, volume was great, then, when I hit my first B note, there was a crackilng/farting noise. I played around, and it does this on every B on the fretboard apart from the open B on my 5 string. It does it on both basses. Has anyone experienced this before? An amp having a problem with a particular note?