Grounding in bipolar supply circuits? (please RG,anybody?)

[Aharon]

I have been making tube amps for a while and somehow I'm drawing a blank here when it comes to the grounding in circuits that use bipolar power supplies.

The power supply in question is a 2X15 regulated PSU.
I have +15/-15 and 0V.
The input and output of the circuit are isolated from chassie ground(using plastic jacks).
Do I connect the circuit ground to the mains ground (at some point)or leave it separate?.
How does this work,will I have noise etc?
Thanks
Aharon

[Jason M.]

Yes, ground is 0V.

Connect the signal and circuit ground to the chassis.
I have made several of the Anderton EPFM projects which use +/- 9V and powered them from a DIY regulated supply.

So, what are you building?

J.

[Aharon]

I'm building a pre and a compressor but they are both bipolar suppies so I was wondering,I'm used to not worry because with 9V everything is one ground and with tube amps you tie to only one ground point too,that left bipolar circuits and I was afraid I was going to fry something.
Thanks
Aharon

[Boofhead]

There's a few things which to be cleared up here because it's easy to blur 0V, ground, chassis and mains earth.  On a tube amp they are often all the same.

As far as the circuit connections go the power supply 0V connects to ground.  The sockets grounds are of course part of the circuit and must connect to the circuit.

Whether you connect ground/0V to the chassis is a different issue.  A lot of (modern) circuits don't connect ground/0V to the chassis to avoid ground loops (which can cause humm).  When you don't connect ground/0V to chassis, you connect a 10ohm resistor, and/or a 100nF cap, between the circuit ground and the chassis (many different methods here).  When the circuit is powered from battery or a non-earthed supply it's not such a big issue and in this case you can connect ground to chassis without a ground loop - although you can get problems putting two metal cases on top of one another because they make contact.   The isolated sockets arose from adhereing to the isolated ground wiring schemes and also to avoid hum loops internal to the same box.