To Float or not to Float...

georgehifi

Look at most CD players, tuners, phono stages ect, they mostly have a figure 8 mains plug on the back yes just two pin, and yes it get’s it’s earth ref from the next stage ...

I thought we were talking about components manufactured in this millennium, which typically use IEC connectors and either have safety grounds or special construction to insulate the chassis. It’s rare for modern equipment to use figure-eight, two-prong AC connectors.

You might still be relying on obsolete knob-and-tube wiring in your house, too. But most of the world has moved on from that.

No matter how you to try to twist this discussion, @georgehifi , interconnects are not intended to carry a safety ground. And there is no inherent risk in having a system with multiple safety grounds. The goal is to have equal electrical potential of each ground - rather than to bypass safety grounds.

georgehifi
2,764 posts                                                                       09-13-2017 11:20pm

What if all the AC powered audio equipment uses two pin mains plugs?

Then this is lethal, there must be always a ground.
Look at most CD players, tuners, phono stages ect, they mostly have a figure 8 mains plug on the back yes just two pin, and yes it get’s it’s earth ref from the next stage, the pre if it’s earthed, via "guess what" the interconnects.

Cheers George

No, an earth ground is not needed when the equipment is Class ll (Double Insulated) power rated.

If a piece of audio equipment is Class ll rated the power cord will be two wire. In the US and Canada at least the NEMA 5-15P or 5-20P plug will be polarized so it can only plug into the wall receptacle in one direction.

For detachable power cords there are of number of IEC connectors available.
The C17/C18 15 amp combo is widely used.
https://en.wikipedia.org/wiki/IEC_60320

Picture of power cord with a C17 female IEC connector.
http://www.yunhuanelectric.com/Clkj_Images/upfile/image/IEC-60320-C17-Power-Connector.jpg

Picture of the IEC C18 inlet connector.
http://usr.audioasylum.com/images/1/14409/C18_IEC_Inlet.jpg

Where the inlet IEC is a C18 a 3 wire power cord with a female C13 connector can be used. (Though NO earth connection is made to the equipment.)
https://www.kenable.co.uk/images/RB-291_i1.jpg

Here is a picture of the back of a Marantz PM8005 Integrated amp. Note the inlet connector is non earth grounding.
http://www.us.marantz.com/us/Products/Pages/ZoomImage.aspx?img=/Assets/images/products/PM8005/XL_pm8...

Here is a picture of the back of a Marantz SA8005 player.
http://www.us.marantz.com/us/Products/Pages/ZoomImage.aspx?img=/Assets/images/products/SA8005/XL_sa8...
Note the inlet connector is a 2 wire non grounding type.

NO earth ground connection is used.

~ ~ ~ ~ ~

As for using the small gauge signal ground wire of an IC for a safety equipment grounding conductor.

First the IC cable is not approved to be used as an equipment grounding conductor by any recognized third party testing laboratory. NONE.

IF a ground fault event, from the hot conductor to chassis on the load side of a small amperage value fuse were to occur it is possible the small gauge signal ground wire might carry the current long enough to cause the fuse to blow. Might.

If the ground fault event happened on the line side of the fuse, NO WAY. In the USA the typical 15 amp branch circuit breaker could pass 100 amps before it would react to the ground fault event and trip open. NO way the small signal ground wire of the IC can handle that kind of current. What will happen the small wire will blow, burn, itself free at one end or both where it connects to the connector. If the IC jack on the back of the audio equipment is soldered directly to a circuit board it may melt the solder and the arcing that follows may cause damage to the small circuit trace.

Now what if a ground cheater is used on a big honken Krell power amp that uses a 15 amp magnetic breaker to protect the amp. Do you think the small signal ground wire in the ICs will carry the high ground fault current and cause it to trip open?

Jim

Correction:

If a piece of audio equipment is Class ll rated the power cord will be two wire. In the US and Canada at least the NEMA 5-15P or 5-20P plug will be polarized so it can only plug into the wall receptacle in one direction.

That should read NEMA 1-15P plug. A 125V 15 amp two wire polarized plug.
Example:http://rockyroadweb.company/ebay/2_prong_stereo_cord1.jpg

They make a NEMA 1-20P plug, but I have never seen one.....

Jim

First the IC cable is not approved to be used as an equipment grounding conductor by any recognized third party testing laboratory. NONE.

This is exactly how more than half the source equipment that use earth figure eight two pin mains cable get their earth reference, via the interconnect.
We in Australia have one of the most stringent mains safety rules and regulations as we are 240v (lethal), nearly our sources have their mains reference given by the interconnect, and guess what we don't have many earth hum noise problems, because we don't get many ground loop issues.
We may get a earth loop problem when two mono blocks poweramps amps each have earths and are plugged into different power points who's earths take different routes around the house, this can sometimes create a loop, usually then one is floated (not ideal I admit) or we get longer leads and plug then both into the same power point.  

Cheers George   

This is exactly how more than half the source equipment that use earth figure eight two pin mains cable get their earth reference, via the interconnect.

IF the equipment is Class ll (Double Insulated) Listed that uses a two wire power cord and plug, why do you think it still needs to be earth grounded?

Jim