|Near the input jack on most larger bass amps, there’s very often a button labeled “-10dB” or “-10dB pad”. Sometimes it’s -6dB or -9dB (often seen on Fender bass amps), and sometimes it’s labeled not with figures, but with the phrase “active/passive.” What is that button for?It’s called an input attenuator. If you’re playing a passive bass guitar—that is, one without an onboard preamp and its attendant rear battery compartment—you don’t need to use it.
If you’re playing an active bass, however—the kind with the battery compartment on the back—your input signal might be too hot for your amp, overdriving the preamp and causing the amp to clip. You’ll know your amp is clipping when the sound gets all distorted and weird in an obviously unpleasant way that sounds more like fabric ripping than bass pumping (well, that and when the clipping light starts flashing).
That’s when you hit the input attenuator button, which takes an input signal that’s too hot and chops it down by several dB to an acceptable level that your amp’s input stage can handle much more easily. You still get the distinctive tonality of your active instrument, with a signal level that won’t make your amp clip.
-9 dB input attenuator or “pad” button on the face of a Fender TB-1200 bass head (above) and -6dB button on a Rumble 350 Combo amp (below).