This is one of the best Delay pedals every made, and has the only mod on it that made the pedal better. These are rare, and don't come up often at reasonable prices.

The Line 6 DL-4 is a popular delay modeler pedal that can be modded for enhanced performance. The Keeley mod for the DL-4 includes several upgrades such as fixing the volume drop issue, components inside are replaced for a clearer sound, including Burr Brown opamps, which improve the quality of each delay effect and loop recording. These mods make the pedal sound more pristine and reduce unwanted noise.

It’s worth noting that Keeley-modded DL-4 pedals are quite rare since Keeley no longer offers these modifications.