I tested it with a guitar and with a keyboard. It cut the hi freq. in a very evident way. I compared to a BSS and to a Rupert Neve DI boxes and it is not usable in my opinion. The Palmer DI is much better!
I found a good usage decoupling the sub-woofer of my home theater system. There was an humm caused by a ground loop. I lifted the gnd modifying the wires in the connector and It is perfect for that usage. ;-)