Tech Square

Technical and speculative discussion of amps, cables and other topics.

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

RE: Star Ground Question

Posted by shermanr@prw.net on June 28, 2009 at 13:18:02:
Good safety question.

In using a cheater plug, you are eliminating the Protective Earth connection.

This means that if there's ever is a short circuit on the chassis, or if for some odd reason the chassis of the equipment becomes 'hot', you touch the chassis, the short circuit will pass through you and not through the 3rd wire. Not a good feeling...

If your use a cheater plug, and eliminate a hum problem, then somehow your equipment is finding a path from the Neutral wire to the Protective Earth wire or some other ground loop problem.

The safe answer is NO, don't use cheater plugs, they bypass the safety ground.

If you need a cheater plug to eliminate hum, there's a problem in the receptacle wiring or a ground configuration issue inside of one of your components.

Maybe, inside one of your components, there is a connection between the DC star ground and the 3rd Green wire.

This can happen either at the IEC socket, direct DC ground to chassis at one or multiple locations, via a 0.01uF/1000V Ceramic cap or via a small 10 Ohm resistor between the safety ground and the DC ground.

It's common to find 2 wire vintage gear using the chassis as the DC ground plane. These components can wreak havoc when connected to 3 wire equipment.

Modern DVD, CD, etc. components can only have a 2 wire plug, but it's polarized. And the chassis is completely isolated from the internal circuitry. The internal power supply DC ground is totaly insulated and isolated from the chassis.

A bit of troubleshooting is needed if you are having hum issues, if not, then be assured that if a component has a 3 wire plug, the 3rd wire is there for a very important reason.

If the same branch circuit that feeds your gear is not sharing a light dimmer, these are also notorious noise offenders for our HiFi systems.