But no sorry; can't help other then suggest get the service manual and see what adjusts the 55 has and try and do 'em (and perhaps clean some pots, etc.). I've become an "expert" at doing these on the 45, but was told that the 42/45 was unique in at least one of these (the "damping" adjustment which I'm about to hopefully fix once and for all with the "drift/fix" SB update for that one!).
LR: AudioEngine wireless link from family room preamp to Barcus-Berry 2002R Sonic Maximizer to GlowPower Zyxt IC's to Sunfire 300x2 to Nordost 6M bi-source wires to AOS 28" MDF spherical speakers using six 6.5" woofers and eight 1" dome tweeters symm. arranged around the surface.
SS system: CX-995V DVD to AV-634x 3-4 channel amp (center/rears) & M1.0t mk-II opt2(fronts).
Garage: 300 disk changer to Entech 202.5 DAC to MXR150 Receiver (pre) to TFM-42 to EPI 400 speakers.