Block trained its new speech model on a single Nvidia GB200 NVL72 , a liquid-cooled rack that Nvidia says holds 72 Blackwell GPUs and 36 Grace CPUs. The finished model, called Dessa, runs on a MacBook Pro with an M4 Max chip or better, and everything it knows came from human conversation, with no text and no pretrained model underneath.

Block’s in-house AI lab put Dessa online Thursday with a demo site full of recorded conversations. Jack Dorsey, Block’s co-founder and chairman, promoted it on X that afternoon and added in a reply : “this is big (but also really really small…small enough to run on your macbook).”

Why it skips the text step

Most voice assistants work as a relay: one model transcribes the caller, a language model writes the answer and a text-to-speech engine reads it back. Nvidia’s open Nemotron Voice Agent blueprint is built that way.…