An 8×10” Fender bass rig powered by a TBP-1 Tube Bass Preamp (top) and an MB 1200 Power Amp (bottom). When powering up such a rig, the preamp is turned on first, followed by the power amp. When powering down, the power amp is turned off first, then the preamp. This order of operations pertains to all preamp-power amp combinations.
For guitar, bass, keyboard and PA gear, if you use a separate preamp and power amp, there’s a certain correct order of operations when turning devices on and off.
First, you must turn the preamp on before you turn the power amp on. The reason is this: Were you to turn the power amp on first—before turning on the preamp, that is—the power amp could then amplify the electrical surge and “pop” when the preamp is turned on, possibly to the tune of hundreds of watts of power. You don’t want that to happen. At the least it could be annoying; at worst it could damage your gear.
Conversely, when powering down, you must turn off the power amp first and then turn off the preamp.
OK, so, remember: The preamp is the first thing on and the last thing off. The power amp is the last thing on and the first thing off.
This order of operations follows the conventional sound reinforcement wisdom that you power up from the start of the signal path to the end, and power down from the end of the signal path to the beginning.
If you use a pedalboard, for example, you’d want to power it up before you turn your amp on, and then power down your pedalboard after you turn your amp off. Or, when setting up a PA system, you’d power up the mixing board, compressors, EQ, etc., before turning on power amps or powered speakers; when tearing down, you turn off the power amps or powered speakers before turning off anything else.
For a replacement on/off toggle switch, click here.