All who say preamps are invalid err and slander tone. The Zwingli SDD-3K Preamp takes the preamp from a certain popular 80s rackmount delay and swaps the toggle switches for knobs for more flexibility. Use it as an always one to get that certain “Edge” in your tone (Make it meatier, if you will), or set the Zwingli as a solo boost. Also features soft touch relay bypass.