Catalinbread Topanga Classic Spring Reverb PedalThe Catalinbread TOPANGA gives you the classic three knob controls. It also includes a great discrete preamp that you can control via the Volume knob for a healthy amount of great clean boost when you want it. Dwell Knob The Dwell knob controls how much signal is going into and driving reverb springs. Tone Knob The Tone knob allows you to roll off just the right amount of high end from only your wet signal. Roll this knob back if you want the reverb