Program Equalizer and Microphone Preamplifier Eighteen’s preamplifier circuit isn’t just another clone, but an original design built to pay proper tribute to some of the most classic designs ever made. The Eighteen starts with a Cinemag input transformer, but that’s far from where the magic stops. In order to get the absolute perfect sound we were looking to achieve with Eighteen meant a bit more work under the hood. This is where our new BLA1831 custom, discrete op-amp comes into play. Through an extensive period of component matching, we were able to create a custom op-amp that matched the vibe we were aiming for, while still matching a noise floor that is akin to modern equipment. The preamplifier also features polarity inverse, 48V phantom power, an 80Hz high-pass filter, and a 10kHz low-pass filter.