To Float or not to Float...

georgehifi
2,763 posts                                                                    09-13-2017 5:08am

 This is extremely dangerous - interconnects are not intended to carry safety grounds.

No it’s not as many sources have two pin mains plugs and rely on the ground from the next stage via the interconnect same goes for some preamps.

What if all the AC powered audio equipment uses two pin mains plugs? (There in the equipment uses internal double insulated AC power wiring.)

The safety equipment ground is for electrical safety. It is not needed for the operation of the equipment electronics or SQ, (sound quality), of the equipment. In fact sometimes an equipment ground can harm the SQ of audio equipment. It can introduce noise and of course, as cleeds said in his last post, it can cause a ground loop when a difference of potential, voltage, exists between equipment grounds.

weebeesdad OP
54 posts                                                                            09-12-2017 12:48pm


Thanks for all of your responses. Cleeds triggered the solution when he (or she) wrote "a properly grounded power cord", which reminded me that I was having intermittent problems with the connecting plug of the preamp’s power cord. Swapped out the power cord and problem solved. I also have a pair of DeHavilland mono block amps with the same ground/float switches, and in the manual it states that leaving the switch in the "float" position may result in a "cleaner sound". At any rate, a fully functioning grounded power cord has done the trick...

Cleeds triggered the solution when he (or she) wrote "a properly grounded power cord", which reminded me that I was having intermittent problems with the connecting plug of the preamp’s power cord. Swapped out the power cord and problem solved.

It may have stopped the buzzing but it, just my opinion, is only a band aid that stops the buzzing. Just a guess on my part you may have a cold solder connection internally with the return signal ground output jacks on the preamp. When you close the ground lift switch the signal ground connection is being completed through the power cord equipment ground wires. There in the signal ground of the equipment is connected to the chassis of the equipment. The safety equipment ground is connected to the chassis. (If designed properly the signal ground does not connect directly to the chassis. May be through a resistor). When you close the ground lift switch on the preamp you completed the signal ground circuit from the preamp to the power amp through the power cords equipment ground wires. Preamp power cord >> to the wall receptacle "U" shape equipment ground contact >> to the power cord of the power amp.

Jim

Cleeds wrote:

This is extremely dangerous - interconnects are not intended to carry safety grounds. Following this practice means that a component's chassis could be energized with lethal voltage. Safety grounds should be "earthed" only through a properly grounded power cord, or a chassis that is itself directly connected to a safety ground.

This is absolutely correct, and it amazes me that audiophiles will accept a potentially lethal component in their house.  Interconnects are not designed to carry a safety ground.

There are several techniques for eliminating ground loops while at the same time having every component's SIGNAL ground connected to the SAFETY ground (i.e. the chassis and ground lug of the mains outlet) .

Look at section 15.10 of the document downloadable on this page for one sample solution:  http://www.valvewizard.co.uk/Grounding.html

It would be easy to retrofit the above suggested circuit (4 parts) into a vacuum tube component (especially one that's hard-wired).

Cheers,
Thom @ Galibier Design

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  

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.