Can confirm that the shottky's, choke and good caps are a good thing.
Also you will want to try bypassing each of the schottkys with a .1mf good quality cap and the other thing I have tried is to balance the centre tap of the HT.
There are two red colored wires coming from the power transformer to the rectifier tube and a red/yellow that is attached to the ground bus. If you measure the resistance from each of the red wires to the ground bus they should be the same (but they are not becuase one wire is slightly longer than the other - they are wound over each other) - this caused a ripple to get into the supply that cannot easily be filter out. The way to cure this is to add an equalisation resistor to one leg. In my case I measured 54 ohm on one leg and 54 ohm on another - so I added 3 ohms to one leg.
Try it!
Red....
