The Tube Microphone Preamplifier, or Tube MP, controls the sound created by a microphone before it hits the amp. For mics that need phantom power - this unit provides it. Even if you don't need phantom power however, the Tube MP is still great for getting a full, rich, warm tube sound - plus, it offers another 70 dB of gain. The Tube MP is a must if you are using our OM500 mic and you're going to plug directly into am amp, but it can be used with other mics and equipment as well.