Why do some manufacturers reverse preamp polarity in the first place?


My Rogue RP-5 reverses polarity, so I switch the pos / neg at speaker terminals. The manual does not mention this, however, I wrote the company and they the amp does reverse the polarity. 

Now my question is...why? I would say 98% of buyers of this amp do not know to reverse the cable connections. I would say most reviewers did not as well. Yes, I realize, polarity reversal is not noticable in most instances. Especially, since many recordings are all over the place when it comes to polarity (at least that is what I've read).

So the question remains...why...why not just have the amp terminals set up so the buyer can just plug in as normal?
aberyclark
A point that hasn't been mentioned is that when the setting of the polarity switch that is provided on some components is changed, in addition to the polarity of the music signal being inverted the sonics of the component could conceivably change, at least slightly, depending on the specific design.

I'd expect that to not be the case with a fully balanced design, such as Ralph's (Atmasphere's), since polarity in such a design can be changed by simply interchanging two signals somewhere in its internal signal path.  But with a design having an unbalanced internal signal path it is not necessarily that simple, and in some designs I wouldn't be surprised if sonic side-effects were to occur when the position of the switch is changed.

Perhaps in some cases that is one example of how easy it can be in audio to attribute a perceived difference to the wrong variable.

Regards,
-- Al 
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