I think their function is as a shield, not as a damper. I've had a couple of vintage amps that use a single metal-can shield only on the input/"gain" tubes. Then again, most modern amps don't seem to bother.
Not sure if they're necessary in this case, as I doubt they're using those 12AX7 tubes for gain - though it seems an odd choice of tube type for a line-driver.
Not sure if they're necessary in this case, as I doubt they're using those 12AX7 tubes for gain - though it seems an odd choice of tube type for a line-driver.