Shop Favorite FAQ Policies Contact MXR M87 Bass Compressor Phantom48 is proud to be an Authorized MXR Dealer! Take your favorite studio compressor to the stage with the MXR M87 Bass Compressor. A complete array of controlsâAttack, Release, Ratio, Input, and Outputâmakes it easy to fine-tune your sound, from subtle peak limiting to hard squashed compression effects. Its CHT⢠Constant Headroom Technology gives you plenty of headroom and clear performance.