Analoguetube builds and manufacture's classic tube technology of the 1950's and 60's using traditional electronic methods with parts that are sourced commercially and that are commonly available. The AT-1 provides a repeatable *stepped* 21 position AC threshold control particularly useful when linking 2 units together and recalling tracks. The control has 21 steps with a 1% accuracy per division. The External *Key* input provides access to the compressor side chain input with