So this is a very simple device. It varies the input impedance your guitar or bass "sees." it varies the electrical load on your pickups so that the guitar feels and sounds more like it does into an amp.
What does that mean? Well on my simple home rig I've done a lot of direct recording and could never get a sound I liked. The guitar always seemed "thin" and a little plinky. I have a decent Direct box, an Avalon U5. But even with the avalon I was unhappy with the direct sound.
The Dragster solved the problem. It's a ridiculously simple device. Plug the guitar into it, then plug it into whatever is feeding your DAW. There's a little thumbwheel labeled "less" and "more." Dial it all the way up to "more" and the tone gets muddy and weak. Dial it all the way to "less," and the tone gets' louder and thin. There's a sweet spot, where the tone has "body" and range but isn't thin or plinky. That spot is different for every guitar. but the end result is really great direct sound.
A couple notes: there's nothing to this device. Open it up and you see it contains s single resistor. That's it. You could make one for the price of two jacks, a thumbwheel pot, and a resistor, and a metal case. The dragster generally sells for 49.99. You could build it yourself for less. But think about your time, what's that worth? And the box itself is sturdy, compact and east to mount. So IMHO it's worth 50 bucks. I paid 20 for mine, which I found used.
It doesn't have any marking or gradations on the thumbwheel, So you have to set it by ear each time-there's no "recall" marks. But that's why you have ears.
So bottom line--simple device, does exactly as advertised, really effective, worth the price. Best bang for the buck of any piece of gear I've ever bought, except maybe those clamp on the headstock tuners