Amp making an unusual noise (hum, buzz, or rattle)

Every so often we hear that an amp is making an odd sound — a hum, a buzz, an internal rattle. It's rare that the amp itself is the source, so it pays to troubleshoot the whole rig. Start with the usual suspects: - Instrument / pickups. A little fizzy buzz until you touch the strings is normal — your body grounds the guitar and kills it. If holding the strings doesn't reduce the buzz, move on. - Cable. Hum or buzz often means a cable going bad. Plug into your guitar and turn its volume all the way down — it should be as quiet as the amp with nothing plugged in. If there's still hum, gently flex each end of the cable; if the hum changes, the plug terminations are failing. Also try grasping the cable in the middle without touching the strings — if the hum increases, the shielding isn't doing its job. If it still persists after standard troubleshooting, go further: - Run the amp by itself. Power it on with no instrument and no pedalboard connected. If the noise disappears, it's 100% something in your rig. - Run the amp by itself through headphones. This also rules the speaker in or out — if the noise vanishes with headphones and no load, the speaker is the source. - Run the amp in a different room or building. Bad AC or a bad ground in your building can cause noise. If it's gone elsewhere, that's your answer. Please do all of this before sending an amp in — an enormous share of units we receive for noise perform perfectly on the bench.