SWL3600
Super Member
It may be a piss-poor volume control. Lower-end models, like the 2230, don't exactly have a high-end volume control and L/R tracking is commonly off at lower volumes. I'd bet it gets better as you turn it up. If so, you may have to live with it, or see if you can fit a new volume control in there.
I have this issue with my Marantz Model 3600 preamps. If the volume is too low....and I mean pretty low....the center image will always favor the left side. Drives me nuts. Since most of my listening is from my PC, I keep the volume up enough on the Marantz to keep the image centered and turn down the volume on my PC to compensate. Works well.