Well, without knowing what the product is - Sony uses the "Walkman" name on all their portable audio and video players - and what those acronyms that you stated from the manual mean - it's still probably fine.

The only thing to remember is that rechargeable batteries such as AA are usually 1.2 volts compared to alkaline 1.5 volts, so the product may give a low-battery indication sooner or not operate as long - so, just recharge them!

Daisy -- We use rechargeable batteries for many things, but our camera and one other 'gizmo' won't work with rechargeables -- because, as Bill has already said, rechargeables have that teeny bit less power. For instance, if your Walkman requires 3 volts, it may only get 2.4 volts from two rechargeables. -- Sue