To get the Avalon sound, use the LALA (an opto-compressor similar to the one inside the 737) and follow it with the SSQ or Patron (for that smooth, musical EQ).
It captures the "warmth" and "slow" compression style that the Avalon is known for. B. Variety of Sound: PreX & Baxter EQ avalon vt-737 plugin free download
There are two main "official" emulations: and Kazrog . While they are paid products, you can get them for free using these methods: To get the Avalon sound, use the LALA