Some Thoughts On Vacuum Tubes; Mounting Instructions - PRESONUS BLUETUBE User Manual

3 . 4 S O M E T H O U G H T S O N V A C U U M T U B E S
The Blue Tube comes supplied with a 12AX7 vacuum tube
that meets or exceeds the stated performance criteria for the
unit. We expect some owners of the Blue Tube will try
different tubes to investigate the various performance
possibilities they might provide. Tube replacement can be
easily accomplished by first unplugging the unit from the
electrical outlet and removing the screws which attach the top
to the chassis. The tube is mounted in a transverse fashion
and care should be taken to properly align the pins on the
tube to the corresponding holes in the receptacle. Make sure
the tube is completely seated in the receptacle and replace
the top of the unit before restoring power to it. Remember:
Tube life and performance are affected by how often a tube is
used and by how hard the tube is driven when in use. Signs of
wear may be exhibited by poor performance or by the tube
becoming "microphonic". Periodic replacement of vacuum
tubes is recommended . The time between the suggested
replacement varies greatly with use. If you notice a
deterioration in sound quality then it's time to change the
tube.
Mounting Instructions for the PreSonus Custom