Ground Lift query

[polsol]

I have put together an external PSU for a preamp. Mains input is via a Roxburgh RIR-022-H IEC suppression filter. The rest comprises an on/off switch (dual pole), Toroid, LM317/337 voltage regulator and finally via a ground lift circuit (Rod Elliott design back to back diodes/10 ohm resistor/100nF cap) just prior to the PSU outlet.
I'm finding a significantly higher noise from the ground lift than from the chassis earth.
The following 'scope grabs show:
Chassis Earth in Yellow, Ground lift in blue
1) The PSU without any connections
2) The PSU with the mains cord connected but not switched on
3) Mains power on and the PSU itself switched off
4) Both the Mains and PSU switched on
5) Shorting the ground lift circuit to earth

Perhaps the Ground Lift is incorrectly placed prior to the outlet (after the voltage regulator)?
Might it be better to connect just after the mains inlet? Between Toroid and voltage regulator?

Scratching my head at this point. 😕
Any ideas?

Many thanks
Tony

Edit:
Sometimes one can't see the wood for the trees.
The 10 ohm resistor in the Ground lift is connected to a buss-bar and was not fully secure. 😱
Tightening the screw has removed the problem and the ground lift now acts as expected and there is little difference now between it and the chassis ground (± 260 vs 150 uV respectively).

 

[JonSnell Electronic]

Ground lift is only used on balanced line systems as it is not necessary if wired correctly.