[marty_ell]

On some 1115's I have found h.f. noise may be injected into V1 if heaters are supplied from a floating winding on a transformer without an electrostatic screen in the PSU unit. It's a small effect, but noticeable if you are aiming to tweak the 1155 for top performance.

The simple solution is to make sure the PSU's heater output wires are kept close together (better if strapped as a pair in the cable bundle, even better if twisted) and add an a.c. rated cap between pins 3 and 4 right inside the Jones socket, 10n-100n is fine.

I have also come across one 1155 where some previous owner had rewired the set's heaters to be completely isolated from chassis, I'm guessing this was because the PSU had one side of the heater output already earthed. A poor choice.

Cheers, Marty