Electro-Harmonix LPB 2ube

The Electro-Harmonix LPB 2ube is a pedal-based stereo tube preamp for use with unbalanced line or instrument sources, including guitars and basses. The all-tube signal path (using 12AX7s) has two valve stages per channel, and is run at a high voltage, even though the external power adaptor might seem to indicate to the contrary. The circuit has been designed for a nominally flat 20Hz-20kHz response.

A rotary switch sets the input level between Lo (instruments) and Hi (line), while two pots per channel provide Drive and Volume control. Overdriving the tubes can create anything from warmth to noticeable distortion, and the Right/Mono input can be used on its own, allowing a single input to be fed to both channels. Furthermore, using a cable to connect the right output to the left input places both channels in series for seriously overdriven sounds! The lack of balanced I/O and proper metering may put some studio users off, but with short cable runs noise isn't really an issue, provided that you take precautions against ground loops.

I found the LPB 2ube to work well as a DI box, adding a minimum of noise. At lower drive levels, and it firmed the sound up nicely, retaining punch and clarity. Because the unit is capable of subtlety, it also works well as a mix processor, but if you drive it to the point where hard distortion is audible, it really needs to be used in conjunction with a guitar amp or speaker emulator, as the upper harmonics of any unfiltered distortion can sound pretty nasty. Overall, however, the unit adds weight and clarity rather than fizz and mud. If you find software tube fakery unconvincing, then try the LPB 2ube.