"The Mag-Echo pedal simulates tube tape echo sounds by using the delay circuit and a little bit of modulation. Tape echos have long been regarded as a warm and very guitar friendly form of delay. The Mag-Echo achieves similar results by using a touch of Lo-Fi delay, a slightly filtered echo response to keep things warm, and some modulation. Modulation, or “Wow and Flutter” in the tape world is a slight pitch shift or wavering that occurs as the tape is pulled across the heads. The modulation we use is similar to what we use in our Seafoam Chorus, a slight wavering of pitch on the trails of the repeats. With a simple set of controls for the delay – Time, Regen, and Level and with the “Wow and Flutter” controls – Depth and Rate you can create some very vintage or rather unique tones"
PedalPCB's schematic, info and pcb available here.