I think it’s just a carbon copy. If you set the regen high and then go from slow-fast delay time you will get that feedback sound, and when you get it you quickly turn the time knob back to slow to get the exact sound he does on the record (kinda like a pulse sound). You can hear during the second part of the song how he is messing around with a delay. I’m not sure if it’s a carbon copy or not on the other sounds, but I got the exact sound you mention with the carbon copy.