Microphone to stompbox

MicSplitSigOver the years, I’ve seen dozens of posts within audio forums asking about ways to plug professional microphones into guitar amplifiers and/or effects pedals. The answer is always “You need a microphone preamp!”. The problem with that has always been the form factor and cost. Nobody wants to drag an expensive rackmount microphone preamp out to a gig. Even if you did do that, good luck finding a sound guy willing to let you experiment with his microphone setup. I think I have a solution….

I’ve developed a stompbox sized microphone splitter/preamp/buffer in-a-box. If you take a look at the crude drawing above let’s start at the microphone on the right and work our way to the left:

  • The microphone plugs in to the box via a Neutrik XLR connector. The microphone signal is split two ways via a Jensen or Edcor transformer. One side of the split signal is fed to a mixer (or recording interface). The mixer (or recording interface) will supply phantom power if you are using a condenser microphone. This side of the signal can be sent to PA system (or recording interface) as your “clean” channel.
  • The other side of the split signal feeds a TI INA217 based microphone preamp. It’s a super clean and detailed sounding IC. It is at the heart of several high dollar microphone preamps on the market. This chip is capable of providing 60db of clean gain.
  • After the preamp stage the signal feeds into a buffer. This buffer provides an unbalanced low impedance output capable of driving long cable runs and complex pedal board wiring without “tone suck”. You can plug this in to your guitar FX, to your guitar amplifier, your computer soundcard, your home theater system, the aux input in your car…anything looking for an instrument, aux, and/or line level signal (just adjust the gain on the box).
  • The stomp switch mutes the output signal (the signal feeding your guitar FX/amp/etc). The signal that is going to the mixer is always active.



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