The original Chase Bliss analog delay. Highly regarded modern classic for a reason. The core sound of the delay repeats just sounds amazing. The red knob version doubles the delay time by adding in two more of the highly sought after MN3005 bucket brigade chips. By doing this the original intended core voicing was altered quite a bit. Brighter, cleaner, more prominent repeats. The Blue knob version is warmer for one thing. Has a unique slight grit that just adds to the overall sound. The repeats degrade a little faster, making this one better for delay that melts so beautifully into a dark murky ambiance. Sounds wonderful as an analog chorus/Vibrato. Without using the dip switches it's still amazing but it opens up a whole new world to explore if you do.