The problem with this is that, to judge sound quality, you HAVE to compare at identical volume levels (you know about the 'perceived EQ/Vol curve' thing your ears do, don't you?). If the sound LEVEL changed a 'world of difference' when you went to the two cords and a mixer approach, you aren't REALLY comparing apples to apples...

Now, don't get me wrong, I'm not saying there ISN'T a difference between mono out and external summing to mono, but without eliminating this variable you can't be sure...

The other thing that puzzles me about the whole thing is, if this problem DOES exist (and is not simply a result of the volume jump two cords and a mixer will give you), why are Yamaha owners not INCENSED about this issue, and demanding a fix? The electronics to make a true mono signal from a stereo one costs a few pennies, hardly something an expensive arranger can't afford to have on it... And this 'mono out' issue seems to have been out there for at least the PSR3k era onwards.

It seems something that the Yamaha engineers would not ignore, if it WERE true... This is why, rather than endless 'anecdotal' reports of the phenomenon, surely just ONE person knuckling down and actually doing the DAW test would put it to rest once and for all. Either the flaw exists, in which case you have every right to INSIST that, even if they can't fix YOUR arranger, they make sure it never happens on any future model of Yamaha arranger, or it doesn't exist, and is merely a product of everyone's imagination after hearing the sound through a different mixer chain... (and mass psychology in action )

It will only take ONE person to put this to rest. Permanently. Surely SOMEONE gives a damn?