I've used the phrase recently when writing about my recent acquisition of a 2M Bronze...."sounds great and will no doubt sound even better when it's run in...".

Played a new (used, but new to me) record last night (which was mint, incidentally - 1986 pressing with no noise...take note, Amazon) and muttered to my other half "I think the cartridge has run in...sounds like it's come into its own now..."

But what exactly does that mean in relation to cartridges? Is it the initial "run in" down to the minute wear of the stylus after a few hours? Or is it down to the inner wiring of the cart somehow changing/morphing/improving with use?

Genuinely curious to know.