arth shattering as say putting a brilliant power supply in a Kairn but have improved the sound of the amp. Notably, serial number 2700 there was a shim mod that improved sound quality, serial number 4700 (approx) shake proof washers were added to improve grounding and serial number 5179 they added a capacitor on the transformer connector on the main board which further improved sound quality. The new ones do sound better but the old ones are still great. As far as the crossovers, from serial numbers 200 -1165 there is a tad bit of mucking around to convert them to aktiv but under 200 serial number and over 1165 it is a very basic procedure - quite a similar connection as the LK140."