Beginner question: If I understood correctly, the NFB resistor in 5F2-A is 22K. The amp has a NFB switch. When bypassed, the amp is a little too bright and 'wild'. With NFB - little bit too tamed. I figured out that the optimum is somewhere between. Brightness and volume difference is quite significant between NFB on/off. Could a resistor of 10-15K be the answer? If yes, do I need to tweak something else besides the resistor?