The Radial Engineering JDV is a complex direct input box that is unlike any other DI box out there. It has a ton of features - way more than any other direct input boxes that I have seen. There are a bunch of 1/4 inch connections and the unit also has a low cut and high cut filter as well as a bunch of other helpful features that are rarely seen on DI boxes. The Radial Engineering JDV isn't a rack mountable piece of gear as it is a direct input box.
Even though it is more complicated than most direct input boxes out there, the Radial Engineering JDV is still pretty easy to use, especially as far as the basic functions go. It did take me a little bit of time to understand all of the features and to master using them simply because it there is a lot going on. Everything is labeled clearly and it is great to have so many different features as it just makes the DI box more versatile. I wouldn't think that a manual would be needed unless you are a beginner, but I haven't seen the manual anyway so I can't speak to if it is helpful or not.
The Radial Engineering JDV direct input box is probably the cleanest DI box that I've ever used. It doesn't color your sound at all and simply translate the information with crystal clear precision. All of the extra features make it possible to get a wide array of sounds as far as a DI box goes and allows this to be used with pretty much anything that you would want to take a direct signal from. I use the Radial Engineering JDV mostly for recording bass guitar in the studio, but also have used it for keyboards and even electric guitar if I am looking to get a direct signal and add effects or amp modeling later on. I can't say enough about the clean signal that the Radial Engineering JDV will provide you.
I first used the Radial Engineering JDV about a year ago and I was immediately impressed with the great sound quality. It has a slew of features that are very helpful and through and through is one of, if not the best direct input box that I have used. However, you get what you will pay for as this unit will cost a pretty penny for a DI box and is also one of the most expensive ones I have seen. For this reason I would only recommend this DI box for those who are professionals looking for great tone regardless of price. Overall, the Radial Engineering JDV is a great DI box but the price tag is probably a little bit too steep.