If you're looking for a combined pre-amp and DI, with the ability to blend between the two, there's really not much choice. Luckily, though, you don't need to look any further than this little beauty. The fact it's available in a 500-series module means that it's possible to use this kind of gear on the road as part of your instrument set-up, which is pretty astounding. As you might imagine, the thing is built like a tank, and cosmetically looks excellent. The signature Portico knobs are great to grab and feel solid. Before I got hold of one of these, I was using Focusrite ISA units as my main pre-amps, and to be honest, I didn't expect to hear any noticable difference between those and the 517, especially considering it wasn't a dedicated pre-amp itself. However, comparing the sound of an acoustic guitar through a DPA 2011C, I couldn't believe how much more detailed the 517 sounded. On the strength of this, I bought a 551 EQ (also excellent), and I'm also considering buying a few other rack units in this range. Top notch!