The Piano 88 Dual Tube Microphone Preamplifier


Built for Ed Carlsen 

The latest microphone preamplifier from Rerun comes from a request from Ed Carlsen to create a unit that will respond well while recording piano.  Most of the time condenser microphones are used to record piano in the studio.  This means that a dedicated preamplifier doesn’t need a lot of gain but does need to be very low noise and not prone to distortion.  For this preamp I set a goal of around 45dB of gain and tried to keep things as simple as possible.  Due to the restrictions, a transistor-regulated power supply was a must which does add a certain amount of complication; however the benefits of doing so outweigh any hesitations.

The name come from the fact that I used two different “88” tubes– the ECC88 as output driver and an ECC808 as gain stage.  Of course the fact the piano has 88 keys is just a happy accident!