Cable conundrum: Parasound A21 with RCA AND XLR


Ok, hope someone can give me a lesson. I recently aquired a Sonic Frontiers Line 2 preamp with both unbalanced and balanced outputs. First I hooked up my Audio Metallurgy GA-0 XLR's to my A21 amp, and I was not pleased with the sound. No depth, soundstage was choked. (gain was adjusted) I then connected my Synergistic Res RCA's to the outputs after disconnecting the XLR's. still not that pleased with what I thought was an upgrade.

In an accidental discovery, I reconnected the XLR's to the preamp WITHOUT ever disconnecting the RCA's. BLAMMO!! What sound I got! almost 5.1-like wide soundstage, reach-in depth, and the detail...let's just say i heard things from my CD's I never heard before.

So...how can this be? Both outputs from the preamp go to both inputs at the amp (balanced and unbalanced). Parasound tells me this is not a detriment to the amp. But I thought you could only use one or the other. Not both at the same time.
Any explanation?
evergrey
Well tell us, are you still running both XLR and RCA?

If so how does it sound now?
Sorry for the delayed response. Milpai, i share the same thoughts as you do about this amp. Running through my Sonic Frontiers tube preamp, I feel like i have a great combination of both detail and warmth. The soundstage is very plentiful as well. I gotta say that this combination of BOTH xlr and rca connections really makes that combination wake up. Insofar as tube rolling goes, i was referring to the stock sovtek 6922 tubes that came with the preamp. I'd like to change (roll) these 6 to the recommended Amperex or Phillips equivalent.
My speakers are the next thing to be upgraded, but i really am not sure what to go for. Considering my appetite for prog rock, jazz and tech metal, I am keeping my eye on B&W 803's, Tyler Acoustics, Von Schweikert VR4jrs, Dali Ikon/Euphonia's.....but i am not sure if these are the right combination. I have no ability to audition these locally. What is the speaker choices that other A21 users enjoy?
Re-opening an older thread. I have ordered a pair of XLR cables to go between my preamp and the A21. Of course, they are Signal Cable Silver Resolutions.
Very keen on knowing what others have experienced when they switched from RCA to XLR on the A21.
A shot in the dark -- any chance you dropped your effective input impedance to the A21 in half by using 2 parallel sets of interconnects? This shouldn't tell the tale, since the SF output impedance is pretty low (~ 150 ohms) and the A21 input impedance is suitably high (33 kOhm & 66 kOhm, depending on which inputs you use), but you never know. Is the amp seeing the preamp "halved"?
My path of discovery with Xlr's vs. Rca's to my A21 was the XLR's where a more refined and taller image and increased separation between instruments, plus a lower noise floor. Last year I added a HFT Silver Star fuse for the main ac line. The cables used for the comparisons at the time where AQ's Columbia XLR & RCA I then switched those out for Morrow Audio's MA3 XLR's which where a better synergistic match in my setup to reveal the A21's musical prowess!