When my fender rumble 25 combo amp is turned on and I then plug my bass or my son's guitar into the input jack, there is a LOUD pop. Then everything sounds fine as I/him plays. Likewise when we unplug the guitars and it is turned on. We get around this by only plugging in or unplugging when the amp is turned off.

If we turn the amp on after we plug in, there is no pop.

Does this happen for all combo amps, or is there something wrong with mine? Also, I'm pretty sure the electrical outlet is not grounded. Could that be why it pops?

  • 2
    Using amps without an earth (ground) connection isn't a sensible idea. Often amps do pop when something is plugged in, especially when the jack is put into the guitar. It's best to turn the amp volume to 0 before, but it does sound like there's a problem.
    – Tim
    Dec 20, 2017 at 16:37
  • @Tim, I just tested a bit with it. With the amount volume at 0, I plugged a cable into the amp and it didn't pop. But when I touched the other end of the cable it did pop and hum. And by touch my finger, I mean I bridged to two metal halves of the 'male part' together.
    – rjholtz
    Dec 20, 2017 at 16:43
  • 2
    yeah... don't do that.
    – Tetsujin
    Dec 20, 2017 at 16:55

1 Answer 1


This is true for all kinds of amplification equipment. The last thing you do when setting up musical equipment is turn on the amps and the first thing you do when packing up is turn them off.

Also electrocution is a very common cause of accidental death among musicians. Get a simple electrical outlet tester and use it for every outlet you haven’t already tested for the test of your life. Don’t plug into bad outlets. Literally the first thing I do at a gig after moving my gear on stage is test outlets.

  • 2
    I have always used, since the 80s, a BBC ['scuse the language, their term, not mine] 'buggery box' which is an isolated 1:1 transformer - for a shock-free & hum-free life.
    – Tetsujin
    Dec 20, 2017 at 19:33
  • This is also why many amps have a standby switch. So you can turn on and plug in, and then bring the output stage onboard in a controlled manner.
    – Doktor Mayhem
    Dec 21, 2017 at 18:12

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