The design of the unit went through numerous changes, taking a while to hit its stride. The originals were somewhat noisy, prompting Brad Plunkett of Urei to design the Low Noise circuit that gave the unit its ‘LN’ designation. Improvements continued to be made over the years, with the result that there are 9 major revisions of the vintage 1176, given the letters A, A/B, B, C, D, E, F, G, and H. The substance of these revisions is detailed below, gleaned from the Universal Audio website.
Based on the look of their faceplates, Revisions A, A/B, and B are all nicknamed the Bluestripe, since they all featured a section of blue paint around the VU meter. Revisions C to G all have the nickname Blackface for their black anodized aluminum, while the final Revision H is known as the Silverface, for its natural brushed aluminum. Most units include the revision letter with the serial number on the back. Revisions C, D and E (the first three with the LN circuit) are all very similar, and are historically the most beloved.