Using a bridge rectifier to break ground loops

[Baz1984]

Hey all,

In my diy cornish style pedalboard I'm having all sorts of horrors with ground loops and noise. I have been looking at installing a transformer and then adding the loop busting diode bridge discussed in section 5 here. 

https://sound-au.com/earthing.htm#s6

I was looking at installing a tirodal transformer, but this article advises against it (from what I understand) just wondering why?

Baz

[antonis]

Rod Elliott deals with power amps, heavy currents & transformers of hundrends of VA..
For a pedalboad, the use of a busting bridge rectifier is an overkill..

Maybe you'll have to check Spyder on GEOFEX..
http://geofex.com/article_folders/oldspyder/oldspyder.htm

[Baz1984]

Cheers for that info. I've seen the spider, I'm trying to trace transformers in the uk. At the mo I'm using a switch mode and screened wire so was going to put the 10 ohm resistor off the screens to the boards, ferrite choke and and lc filter.... then that is still. Noisy I'll look at maybe a 2 or 3 way transformer n go from there.... thre is about 15 different boards in the box so hoping that I dont need to have a 15 way transformer.

Baz

[Rob Strand]

In principle you only need the cap and the resistor.   However, for a mains powered device a mains fault can cause the ground voltages to be at different potentials.   That's a safety hazard.   The bridge rectifier covers that case.  That's why a high current rectifier is used in a circuit which normally does not conduct any current.

[merlinb]

I was looking at installing a tirodal transformer, but this article advises against it

Nothing wrong with toroids, and that article does not advise against it.

[antonis]

What Rob said..

[R.G.]

N.B.: As Rob notes, the diodes have to be high current types. The safety standards say that to pass, a grounded chassis fault must carry a 25A fault current and still keep the grounded chassis at less than a few volts. This is to ensure that the AC mains wire will not make the chassis hazardous and still conduct enough current to pop the fuse or possibly the wall socket breaker. A 20A or preferably more diode bridge could do this.

Re Toroids: Toroids are fine. They do have issues with any small DC offset on the primaries that EI types don't.

[Baz1984]

Thanks for the advice people. Will be having a play around on friday and see what happens... hopefully.

Baz