Warmth is usually the result of the electrical noise generated by analogue gear. There are plenty of software processing plugins to simulate this, and they get

Warmth is usually the result of the electrical noise generated by analogue gear. There are plenty of software processing plugins to simulate this, and they get pretty accurate, but it does amuse me that producers spend an inordinate amount of time and money trying to reproduce the sound of a valve amp or an analogue synth when they could just go out and buy a valve amp or an analogue synth.