@OP, there's no way to tell except by listening. MWH777's post explains it well. To the extent that it is audible, the effect is likely to be more obvious by playing some simply mic'd recordings .
Invert ?
I’ve owned the Audio Research Ref 6 SE for about a year or so. One thing I don’t understand is the Invert switch. What is this used for exactly. The manual doesn’t not go into detail at all. Actually I’ve always been afraid to use it thinking I may damage something. Thanks in advance