How do you scale content production with AI without losing your brand voice?

Our marketing team of 6 can't produce content at the pace our growth target requires. We need 3× the output. I've tried giving the team access to ChatGPT and Jasper — output increased but everything we publish now sounds like everyone else. Our brand voice is specific and it's a genuine differentiator. How do marketing leaders scale content volume with AI without the brand getting flattened into generic AI-speak?