This is a must have in any studio for anyone serious about recording. PreSonus Bluetube Stereo Mic Preamp Pre Amplifier version I. This unit is in excellent condition and perfect working order. Upgraded with an European made JJ tube last month, so it now sounds definitely than new. The JJ tube warms up the sound much better than the crappy stock tube. Two channels stereo. Has both TRS and XRL balanced and unbalanced outputs for each channel. Very versatile. It will definitely improve your recording, great for vocal and instruments. The unit works perfectly without any issue. The original power supply is included. See the manual for the Bluetube preamp version II here: /media/manuals/11_BlueTubeDPManual.pdf The unit for sale is the same as the version II, except that version II has UV meters. But compared to the version II, version I is much easier to replace the tube and maintain. The Blue Tube is a mic preamp with tube warmth and features galore. It is a solid, good-sounding, easy-to-use unit that covers a wide range of applications. The Blue Tube serves as a microphone preamp, instrument DI, phantom-power supply, polarity re-verser, distortion box, signal splitter, and signal amplifier for long cable runs! An affordable, quality, 2 channel tube preamp from Presonus!