Related Clues:

• Increase the intensity (with "up")
• Current measure shown by a member?
• Sound magnifier
• Concert volume booster
• Excite, with ''up''
• Bass player's accessory
• A mic might plug into one
• Electric bass accessory
• Band's sound booster, for short
• Unit of current, in brief
• Volume-boosting box
• iPod part
• Box for a rock band
• Intensify, with "up"
• Music festival box