Cable conundrum: Parasound A21 with RCA AND XLR

I have a Parasound C2 preamp processor normally connected to a Parasound A23 amp using balanced cables. My ground switch was and is in the normal position and the cable switch set for balanced cables. I decided to try adding a set of unbalanced cables between the C2 and A23 based on Evergrey's post. The sound seemed fuller and more detailed through my Salk SongTower Speakers with both balanced and unbalanced cables connected whether the amp was switched to the balanced or unbalanced cable position. The unbalanced position sounded slightly better to me when the sound level was matched.
I do not believe the position of the ground switch is the explanation since mine is set to normal (not lifted). I have noted that even when the switch on the amp is in the wrong position for the type of cables used (that is unbalanced if only balanced cables are used or balanced if only unbalanced cables are used) there is some sound output albeit at a lower level. It may be that the amp is being input by both sets of cables although one at a much lower level that for reasons unknown to me gives a richer sound at the same volume. Then again this may be a placebo effect. In any case it was worth trying as I had the spare cables available. YMMV.

Well, this investigation has taken a turn for the worse. I decided to remove the Synergistic RCA's from te amp and turn the ground switch to 'normal'. After i turned my equipment back on from the cable change, i lost sound out of the left chennel. I've tried every scenario to see if it wasn't my source, preamp, speakers or different cables. I've deduced that my amp blew a channel. The 4 buss fuses inside, although taped uo to hide the filament, seemed to still work because the 2 blue lights on te front panel were lit up, the 'Hi Temp' light was off, and te right channel worked.
This is a total bummer and now i have contacted Parasound to see what my options are.
Thanks to everyone for all your input.
Mlenn, are you going to leave both IC's sets connected? didn't know that it would have a similar result for others or not.

Evergrey, sorry to hear about the problem with your amp. I do not know why this problem would be related to your cable change if the system was off when the change occurred as you indicated. Thanks for the warning and please keep us updated on what you hear from Parasound.

Yes, I plan to leave both sets of cables connected to my A23 for the present, but will continue to avoid any changes in switches or cables unless the equipment is off. I blew the external fuse on my A21 (used in separate HT system) once when thoughtlessly switching from ground to lift with the system on. Fortunately, a simple replacement of the fuse fixed my problem. Lesson learned.

My C2 will sometimes switch into a silent protection mode if I touch the unit or connected equipment and get a static spark. Switching to another source or turning mute on and off returns the unit to normal operation. I appreciate this is likely unrelated to your A21 problem.

Hope you get your amp problem resolved soon.

Mglenn, thanks for the support. I'd like to open the discussion back to this cable discovery. I wonder why this is not discussed more frequently amongst users, in utilizing both XLR and RCA at the same time, if results like this can be achieved. I suspect that the approach of good quality cables in both categories can help achieve some terrific results.

EG, sorry to hear of the left channel problem, which I can't shed any light on.

Re your and MGlenn's observations of improved sound with both sets of cables connected, I suspect that the reason it is not discussed more frequently is that it is specific to your equipment.

I think that MGlenn's observation that significant sound comes through even when unconnected inputs are selected is key. That indicates crosstalk between inputs within the A21, and is most likely an unintended (and non-ideal) characteristic of the design. For whatever reason, though, it apparently happens to be synergistic with the A21's overall sonic characteristics and/or the characteristics of the rest of your systems.

Best regards,
-- Al