first I earth the chassis for safety but why do I need to conect it to my ground... - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 20th May 2005, 09:15 AM   #1
diyAudio Member
Join Date: Apr 2005
Location: AUD
Default first I earth the chassis for safety but why do I need to conect it to my ground...

thank you,
First I earth the chassis for safety(well understood) but why do I need to conect my amp ground (zero) to chassis earth

i.e float or not to float if input and output grounds are isolated from chassis.

What are the reasons first and the advantages and disadvantages please
  Reply With Quote
Old 20th May 2005, 10:16 AM   #2
Account Disabled
Join Date: Aug 2002
Location: Near to the Pacific Ocean
My reason is:

I assume the chassis as a pool of fresh electrons, where I always have my star ground. I connect the input, output, circuit and PSU ground lines (coming separately) to this chassis star ground. And, from there, one line goes to the earth ground (power socket) through the bridge diode or thermistor, which blocks the poluted earth electrons, and at the same time secures safety in case.

Hope my reason will be reasonable.

  Reply With Quote
Old 20th May 2005, 10:41 AM   #3
Jennice is offline Jennice  Denmark
diyAudio Member
Join Date: Jun 2003
Location: Planet Earth
If the chassis and electronics do not share ground, you can have dangerous errors without knowing it. (Example: line voltage levels on output terminals, if the PSU fails - and you could still measure zero on the enclosure.)

EMC. You'll get improved shielding = less noise and less likely to get HF oscillations, which can be triggered by HF signals picked up by your external connections (line in).

I get paid to break stuff. My g/f gets paid to play with children. Life is good.
  Reply With Quote
Old 20th May 2005, 11:03 AM   #4
johnnyx is offline johnnyx  United Kingdom
diyAudio Member
Join Date: Jan 2004
Location: manchester
I always connect the chassis to mains earth for safety, but I thought that if the signal paths were isolated, then there would be no opportunity for creating an earth loop.
In practice though, on a sub amp I built there was hum, which disappeared when I connected the signal ground to the chassis (at the input terminals, maybe that is important). The system used different mains outlets too. In a signal generator I built there were HF oscillations which disappeared when I connected the signal ground to chassis (at the output terminals, maybe that is important).
Now I always connect the signal ground to the chassis, and to hell with hum loops.
  Reply With Quote
Old 20th May 2005, 12:15 PM   #5
diyAudio Member
Join Date: Feb 2005
Location: Way up north, USA
Send a message via Yahoo to northsiderap
Default Another Reason For Grounding

I'd say a good reason to ground a case is:

At your main circuit panel in your house, hopefully you have some 5-25 amp breakers from which your audio outlets are run. The neutral should only be grounded at the panel for best power distortion figures in your mains...

If you get a short, your mains circuit breaker is like a big ol' fuse. It protects you in case you get a short somewhere inside of the case that shorts the mains to ground.

If you didn't have a ground to the chassis, then to the main panel on your equipment, you might have a short from HOT to ground and have your chassis at 120v AC or 220v AC potential.

Picture yourself turning a knob on this high-voltage charged chassis and holding onto your guitar strings or touching another piece of equipment that IS grounded.

You would then become a conductor for all of this potential.... Straight to ground...

Establishing a good clean & 'neutral' ground potential is critical, especially when amplifying small signals... Your amp is probably designed to compare the potential of your power supply to the potential of the mains ground to feed the transistors. Don't want noise there.
Your piece of equip. probably also wants to use the mains ground for reference on loading your audio signal. Bad if ground is not 100% shunted into the earth.
--> Jim <--
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
connecting audio ground to Safety Earth AndrewT Power Supplies 41 30th May 2011 10:50 AM
B1 pre earth safety question (newbie) scorpio1 Pass Labs 2 16th June 2009 04:30 PM
Chassis, ground, earth: connect? starbase218 Solid State 3 14th November 2007 08:56 AM
Parallel LM3886, input ground, power ground, safety resistor and oscillations. markiemrboo Chip Amps 5 9th August 2007 03:50 PM
chassis ground vs. earth ground avid Chip Amps 4 10th November 2006 12:56 PM

New To Site? Need Help?

All times are GMT. The time now is 07:05 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2