You could output speech on the TRS-80 (which didn't even have any analog outputs) by pulse-width modulating 0/1 bits on the cassette port -- in conjunction with

You could output speech on the TRS-80 (which didn't even have any analog outputs) by pulse-width modulating 0/1 bits on the cassette port -- in conjunction with the inherent RC circuit provided by the output circuitry and speaker, you could get barely understandable speech.