Preamp External Power Supply Grounding

[StarTrucker]

What is the proper way to ground an external power supply and preamp?

Do you treat all the circuit and chassis grounds like they are in the same chassis?

Where is the best place to tie the circuit common to the chassis? I've marked point 1 and 2. My understanding is point 1 is not advisable because it injects shield currents directly into the power supply. If you tie the common to chassis at the input XLR on the amp (point 2), won't that leave the PSU filter caps without a chassis connection? Does it matter? Is it better to imagine it all as being in the same chassis, just with some extra lengths of wire and follow regular procedure?

 

[ruffrecords]

The analogue 0V (point B on you diagram) should be connected to the chassis at the same point the mains safety earth is connected (which should be very close to the mains inlet. The chassis of the amp should also have a connection to the PSU and be connected to the PSU chassis where it enters the PSU. See attached file.

Cheers

Ian

 

[Speedskater]

Connect the Safety Ground/Protective Earth to the chassis near where the cord enters the chassis.
Connect the transformer frame to the same point.

Do not connect the DC common to the chassis.
Do not connect the low voltage to the chassis.

Connect the power supply chassis to the pre-amp chassis.

 

[StarTrucker]

The analogue 0V (point B on you diagram) should be connected to the chassis at the same point the mains safety earth is connected (which should be very close to the mains inlet. The chassis of the amp should also have a connection to the PSU and be connected to the PSU chassis where it enters the PSU. See attached file.

Cheers

Ian

Wonderful resource, thank you!

 

[Speedskater]

Oh, dear.
And that paper stated so well.

 

[rp]

You might want to look into a humdinger arrangement for the heater circuit, or a DC heater circuit. I built a preamp with an external psu and AC heaters with a 100 ohm pot (or maybe 250? I forget) as the humdinger. The preamp has a little bit of 60hz hum, and the pot helps minimize it - not always in the same position of rotation. I've never gone in to chase down the remaining hum, but I suspect it might be related to using an unshielded cable for the umbilical run, and having the ac heater wires running right next to the B+ for a long distance (2-3 feet).