Ever the sucker for a silly name, I bought the AKAI EIEIO audio interface - the Pro version - and tried it out on a friend who came around with an acoustic guitar and some songs. I put a Rode NT4 (stereo mic) into two of the inputs and my trusty TLM103 into another. The Rode was fine but the Neumann gave a whine, clearly audible in any silences, at around 2.5kHz. It no longer whines but now gives a hum like a bad earth.

I have swapped inputs, cables and cleaned contacts to no avail. The TLM103 is fine going into my Allen&Heath desk, into a Zoom H4 and into an old Roland 1680. I've tried to replicate the hum with the Rode and with an SE2200a but they both work fine with the AKAI.

I have measured the phantom power output of the AKAI unit and this measures 51.4v at the unit and 51.v3 at the mic (inputs 1&2) and 50.4v at both the unit and the mic (inputs 3&4). The current measures 6.86mA at the mic.

Do you have any suggestions? The TLM103 is fine with every other piece of gear I've encountered and the AKAI works perfectly with every other microphone I have used with it. I'm puzzled!