Found this, from the Cardas website FAQ:
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Cable Break-In
Q.) I have all tube electronics and don't want to leave my system unattended while I burn in the interconnects. Do I need to have everything on and playing music to burn in my new cables? - Nordoff
A.) Only the originating end needs to have signal. The cable will break in even if the terminating unit is off. To break-in the cable it needs two things, signal and stability - it should not be moved. -George
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Also finding other similar posts, so the answer may be "can burn in" without volume. Which would be great for everything but amp components, speaker cables, and speakers.
Was thinking about a cable cooker but given this, I'll just let my system do the cooking.
Not sure what a good workaround for speaker cables could be though.