For sale mint (see what I did there? LoL) cMOY Headphone Amp. Asking $60. As made by Biosciencegeek, it doesn't look like he is selling them anymore (on E.....y). Using Burr Brown OPA2227, 9 volt batteries are set up to run in parallel. Base boost/gain switch, can be powered externally. Plugging in headphones turns it on.