Every instance is minted with its own serial number and its own character, the small manufacturing differences that make this unit sound like this unit and no other.
On the Rack that character runs the length of the signal path. One rack's preamp breaks up a touch sooner. The EQ bands sit at slightly different centre frequencies. The compressor grabs transients at its own threshold and breathes with its own timing. The summing bus has its own resonance and crosstalk, the saturation its own warmth, and even the noise floor takes a different colour. No single one of those is obvious on its own. Together they are what gives a rack its voice.
Every new instance can be a different unit, or it can be the one you have chosen to keep. The Rack button in the header is where you decide.
Saved units live in your Documents folder, a folder per product, so you can find them, back them up and copy them between machines.
A unit is the character. A patch card is the character plus everything you set on top of it. Save a patch card and it carries the unit it was made on as well as the settings, so loading one back gives you a choice: Recall Unit brings that machine back with it, character and all, while Apply Settings Only keeps the unit you are on now and takes just the knob positions.
You cannot choose a unit's character any more than you can choose the character of a real machine. But you can learn it, and you can keep the one you love.
