Diode bridge as loop breaker question

[Tyimo]

Hi!
After a serious grunding noise problem with a tubepreamp and the SEWA mosfet follower amp I was re-reading all my articles about earthing and I found something mistakable thing with the diode bridge coupling.

Mr. Pass wrote in the ZV4 docs:

Note in Figure 6 that we have chosen to isolate
the two channels through a rectifier bridge to ground, with each
channel’s ground appearing on one of the AC legs of the bridge.

As it is in the attached image.

Mr. Rod Elliot wrote:

Note the way the bridge is wired, with the two AC terminals shorted, and the two DC terminals shorted. Other connection possibilities are dangerous, and must be avoided.

as it is in the next attached image.

Now I have only one question:

How should I connect the diode bridge to the circuit grund?

DC legs to Earth - AC legs to the circuit? Nelson Pass
AC legs to Earth - DC legs to the circuit? Rod Elliot

So, Who has true?????????????????????????????

Greets:

Tyimo

[Tyimo]

Here is Rod Elliots version:

[Babowana]

Originally posted by Tyimo


DC legs to Earth - AC legs to the circuit? Nelson Pass
AC legs to Earth - DC legs to the circuit? Rod Elliot

So, Who has true?????????????????????????????

Both.

[Tyimo]

Hi Babowana!

Than why Rod Elliot wrote:

Other connection possibilities are dangerous, and must be avoided.

?????

Tyimo

[Babowana]

Originally posted by Tyimo



Than why Rod Elliot wrote:

?????

When he wrote that, he was unsure of himself . . . ?

I hope the attached sketches show the understanding.
The horizontal flip is always direction-free symmetry.
Either end of (+/-) or (~/~) could go the gnd.

[Nixie]

For a ground loop breaker, besides the diodes you should put a 5 to 20 ohm resistor in parallel, as well as a small cap as HF bypass (0.1-1 uf). Make sure the diodes are rated at sufficient current so that in a fault situation the fuse on the hot mains line blows!

[Babowana]

Originally posted by Nixie


For a ground loop breaker, besides the diodes you should put a 5 to 20 ohm resistor in parallel, as well as a small cap as HF bypass (0.1-1 uf).

Why?

[Nixie]

In most ground loop breakers I've seen, the diodes are there as protection in case of fault where the resistor would just burn out. It's the resistor that's doing the ground lifting--you just need sufficiently different resistances on each of the legs of the ground loop. If you just have diodes, the circuit ground is floating within the one diode drop from earth, with no connection to earth; with a low value resistor, I find it still breaks ground loops, but the circuit tends to stay closer to eart. The bypass capacitor allows earth to sink HF interference. With the scope I see less RF on the circuit ground when the cap is added.

[Tyimo]

Hi Nixie!

For a ground loop breaker, besides the diodes you should put a 5 to 20 ohm resistor in parallel, as well as a small cap as HF bypass (0.1-1 uf). Make sure the diodes are rated at sufficient current so that in a fault situation the fuse on the hot mains line blows!

Thanks! Yes, I know. Rod Elliot wrote the same. Most of time a simple diode bridge (35A) or a thermistor (10R/5W) was enough for me.

Greets:

Tyimo

[Nixie]

The diodes are there for safety reasons. Do not omit them, and again, make sure their current rating exceeds the main fuse sufficiently.