Power grounding question

[Govmnt_Lacky]

Can the center tapped ground from an AC/AC step down transformer be tied to the safety ground of a 3 prong plug?

Didn't they do that with the MXR flanger?

[amptramp]

If you are talking about a centre-tapped primary, NO!

If you are talking about a secondary, everything that connects to it will use that point as the safety ground.  If you use it in an effect and there is a connection in an amplifier (usually through a capacitor), you will get the ground loop from hell.  If anything connects this to the line, either inadvertently or by design, you will short out the power source.  Ideally, the amplifier should have its chassis grounded to the safety ground (because it carries the highest current) and all other signal grounds should connect to it at the amplifier at a single point.  Draw a diagram of it, you will see what can go wrong.

[R.G.]

One of the two whole points of transformers is that secondaries not deliberately connected to the primary are galvanically isolated (that is, the resistance between them and everything else is arbitrarily large.)

So for a transformer with an isolated secondary, yes. the center tap can be connected to AC safety ground. In fact, any of the secondary terminals can be connected to AC safety ground as long as there's only one connection. Two connections to the same place would short the secondary.

[Govmnt_Lacky]

Thanks for the replies gentlemen.

I was referring to the center tapped SECONDARY. So I would be connecting the center tap from the transformer Output to the 115VAC Input safety ground. Kinda like they did in the MXR M117 flanger. They just tied the safety ground from the 3 prong plug directly to the enclosure which was also connected to the PCB signal ground via the in/out jack sleeves   

[R.G.]

That is in fact the way that the vast majority of equipment is grounded. Signal ground is attached to chassis, which is also tied to safety ground.