The RND 517 is a pre-amp with a selectable instrument DI and compressor in the one 500 series module. The 517 has been modeled off the award winning Portico 5017 Mobile Pre by Rupert Neve Designs. The 500 series version, is an extremely versatile unit with phase inverse, phantom power and a fixed setting compressor. One really interesting feature of the 517, is you can blend the instrument and microphone input signals. Whilst the 517 is only single channel module, this can be great for blending a guitar amp and direct signal together in real time.