Each Austin model has a unique output transformer. Each of the 3 output transformers is manufactured slightly differently, and each will give your ribbon microphone a slightly different sound:
 
MODEL 1 – Our AUSTIN™ OTA-2 is custom-wound especially for us in Texas. Fat bottom punch, and excellent mid/high-frequency output. Best for recording electric and acoustic guitars, and bringing-out the warmth of male studio vocals. $299
 
MODEL 2 – The Cinemag CM-9887 delivers slightly brighter highs than our OTA-2, and is shielded in a Mu-Metal can for extra hum protection. It also has the longest wires of all the transformers, making it very easy to install. Best for full-range instruments like piano and drums, or breathy female vocals, without the brittle crispness of a condenser microphone. $359
 
MODEL 3 – The Lundahl LL2912 delivers a wide, flat frequency response with flattering highs, but it's amorphous core emphasizes smooth, natural bass. Best on sources that have very low frequency components, like a double-bass, tympani or baritone sax. $399