Rega Brio R

First define the actual problem. For starters, is the distortion in both channels? equally? different?

By way of a caution; you cannot charge into a modern, SMT amplifier like the Brio R, armed with a crude soldering iron and screwdriver with the expectation of finding anything wrong. If you touch things, short a few connections by accident, try to remove parts and replace them on a whim or hearsay, you can only expect to wreck it and that will cost you a lot more to fix than a properly diagnosed fault with a likely known history.