For example, on a 5F1 or 5F2A the stock NFB resistor is 22k for a 4ohm Speaker Load. For the equivalent outcome with an 8ohm Speaker load, one would substitute a 33k (22k squared). But if using the 5k OT tap rather than the 8K, what does the standard, stock NFB resistor need to be? My ear likes the NFB around 56k, so I currently have a 33k and a 50k pot in series. This is a 5F2A with a 5881 using the 5K OT tap.