Short hum burst in PSU circuit

[Walter66]

Hello, with this PSU circuit, there occurs a swelling hum some minutes after power on.
It just swells to maximum hum and then immediately decongests right to zero hum.
The complete interruption is just three seconds long approx.

Any advise on what to change?
Does it happen because the voltage ramps up so slowly?
Maybe the 820K resistor needs a different value?

 

[JohnRoberts]

Are you talking about mechanical hum in a component? Which component?

JR

 

[Evertide]

Is the load about 6k8?

 

[Walter66]

Are you talking about mechanical hum in a component? Which component?

JR

It's a voltage hum burst on the output of the PSU which is regulary audible for a short time in the speakers of my hifi system.

 

[Walter66]

Is the load about 6k8?

The load is a high impedance tube amp circuit ( which consumes about 13mA) and a parallel connected resistor dummy load on the output of the PSU with a value of 9K4 Ohm to simulate the load of the later completely assembled preamp.

The whole system actually is semiconductor Diode rectified but will be tube rectified in the final amp, so the dummy load draws current from moment zero, but the tube amp will slowly ramp up consuming current.