Well I tried that Maplin link and yep it's working now. Ta. I've had a good look at the Rotel's pot, and measuring the carbon track gives me approx 250K. Looking at the carbon track there's a bit missing in the middle at the top of the travel (centre position), so the wiper at this point isn't contacting the carbon track but is connected to a 4th pin on the pot which is wired to the rotels main board with a flying lead. I think I'm gonna experiment with dual gang pots....but at the mo I'm just confusing the hell out of myself!