Hi Wayne and thanks for the info re KPA500 power supply
The toroid transformer in the KPA 500 takes up most of the space available in the K3-sized cabinet and it is amazing that the developers managed to add a linear regulator and even a 500W amp etc. – hi!
Now toroids are a bit "hard" on the inrush current and I guess some soft-start device has been provided for.
But my main concern is this: Is the toroid rated in such a way that no saturation/overheating will occur with the European mains frequency of 50Hz?