understanding star grounding - Page 50 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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
Reply
 
Thread Tools Search this Thread
Old 23rd December 2012, 10:21 AM   #491
Bensen is offline Bensen  Belgium
diyAudio Member
 
Bensen's Avatar
 
Join Date: May 2003
Location: Belgium, Limburg
Default Ground loop in stereo amp with 1 transfo and dual PSU

Hi there,

I have gone quickly through this thread and tried some proposals, but sofar no succes.

My situation: I'm having two amplifiers with each there own rectifier and cap's, but only one heavy toroidal transfo. Each amp is running perfect and is death quit. But when I'm plugging in both RCA cables comming from a source, there's is slight hum comming out on both speakers. This seems like a ground loop to me, however, I don't see where. The signal ground and power ground are connected on the amplifier pcb by a 10R resistor.

Please have a look at the wiring sheme below. What should I do to get rid of the hum?


Greetz
Attached Images
File Type: jpg Wiring scheme.JPG (85.6 KB, 466 views)
File Type: jpg SAM_0975-compress.JPG (238.8 KB, 457 views)

Last edited by Bensen; 23rd December 2012 at 10:29 AM.
  Reply With Quote
Old 27th December 2012, 07:06 PM   #492
diyAudio Member
 
Join Date: May 2008
That's a tough one. Make yourself aware that the signal grounds for both amps will be connected at the source. Then each of them goes through a separate 10 Ohm resistor to its PSU. On the transformer side you connect the grounds together again. From there you go through another 10 Ohm resistor to the chassis. Is the chassis connected to PE and through that to the source ground, too?

Start by using only one PSU for both amps. Produce a star ground between PSU and amps, and connect the chassis there. Replace the 10 Ohm resistors between signal and power ground with jumpers, if possible. Then add the components back in one by one and check each time.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 24th January 2013, 04:02 AM   #493
dazed2 is offline dazed2  Canada
diyAudio Member
 
Join Date: Jun 2010
Location: Toronto
Sorry for drudging this topic up again, but I spent all day reading this thread as I am building a mono block with separate PSU
Earlier in this thread the follow was presented.
Click the image to open in full size.

No one seemed to dispute this and it looks correct to me.
However, the following :
Quote:
Originally Posted by David Davenport View Post
Hi 454,

You will need a minimum of four wires in the cable: safety ground, + voltage, - voltage and power common (0 volts) no matter if you have an SLB or not, of if you have an SLB, where it goes.

Good grounding practice would have five wires if the SLB were in the power supply chassis, and four wires if the SLB were in the amplifier chassis.

If you want to use an SLB, you can not double duty the power common and safety ground because these are what you want to isolate with the SLB. Also, as I said before, it is not a good idea to double duty any ground wiring.

If the secondary of the power transformer is shorted, that short will be reflected onto the primary and the main fuse will blow. There is no need for an additional fuse to protect the transformer.

Dave
Which one is correct? Would a 5th wire be needed to connect the end of the safety ground back to the SLB from amp to PSU in the configuration shown above?

Also, if the amp and PSU were stacked and the cases were touching would this cause a ground loop for earth ground?
  Reply With Quote
Old 24th January 2013, 04:22 AM   #494
diyAudio Member
 
alevans51's Avatar
 
Join Date: Aug 2006
Location: New Orleans
There is an old method for audio ground we used while I was in the military, and I've seen it in several audio systems. Its the 1 ohm resistor signal ground. What this does is help isolate your audio ground and when I say isolate I mean DB isolation. So static and RF interference is pushed ever so gently away from the audio. Have you ever heard of this technique?
  Reply With Quote
Old 24th January 2013, 06:52 AM   #495
andyr is offline andyr  Australia
diyAudio Member
 
Join Date: Nov 2003
Location: Melbourne (Oz, not Florida!)
Quote:
Originally Posted by alevans51 View Post
There is an old method for audio ground we used while I was in the military, and I've seen it in several audio systems. Its the 1 ohm resistor signal ground. What this does is help isolate your audio ground and when I say isolate I mean DB isolation. So static and RF interference is pushed ever so gently away from the audio. Have you ever heard of this technique?
Yes - except I thought the value to be used was 10ohms?

Regards,

Andy
  Reply With Quote
Old 24th January 2013, 09:27 AM   #496
diyAudio Member
 
nicoch58's Avatar
 
Join Date: Oct 2004
HI dazer2

As you have done the safty chassis heart ground , the only important things! you can float your signal/psu ground....(ie disconnect Psu1/2 from your green line)

but this apply only for diy stuff or mod stuff
__________________
Sic58
  Reply With Quote
Old 24th January 2013, 10:00 AM   #497
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by dazed2 View Post
.........................Which one is correct? Would a 5th wire be needed to connect the end of the safety ground back to the SLB from amp to PSU in the configuration shown above? .............
What is SLB that you and Davenport refer to?
__________________
regards Andrew T.
  Reply With Quote
Old 24th January 2013, 10:03 AM   #498
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by nicoch58 View Post
...............As you have done the safty chassis heart ground , the only important things! you can float your signal/psu ground....(ie disconnect Psu1/2 from your green line) .............
No, you cannot.
All exposed conductive parts must be connected to Safety Earth.
That includes the amplifier chassis and the amplifier control knobs and the input and output terminals and screws through chassis walls and the remote end of an interconnect that your toddler could put in their mouth since the nice red thingy on the end looks just like ......
__________________
regards Andrew T.
  Reply With Quote
Old 24th January 2013, 10:04 AM   #499
diyAudio Member
 
nicoch58's Avatar
 
Join Date: Oct 2004
EDIT : thanks AndrewT

improved I hope NOT SAFETY

trafo with screen pri/sec , dual separate secondary , point ground like star.
one more ground wire between chassis ? probably better
Attached Images
File Type: gif good_ground_manu.GIF (14.2 KB, 298 views)
__________________
Sic58

Last edited by nicoch58; 24th January 2013 at 10:07 AM.
  Reply With Quote
Old 24th January 2013, 10:08 AM   #500
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by alevans51 View Post
There is an old method for audio ground we used while I was in the military, and I've seen it in several audio systems. Its the 1 ohm resistor signal ground. What this does is help isolate your audio ground and when I say isolate I mean DB isolation. So static and RF interference is pushed ever so gently away from the audio. Have you ever heard of this technique?
There was a good set of posts in another Thread that explained where the various GROUND LOOPS could occur and why they would benefit from added resistances in some of the star grounding links.
I cannot recall the author nor the Thread.
But the jist was to reduce the loop current sufficiently that the remaining current and the loop resistance resulted in a much reduced interfering voltage.
In a stereo set up there are many loops and each loop needs attention to get that reduced interfering voltage
__________________
regards Andrew T.
  Reply With Quote

Reply


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
Quick question about star grounding jn2630 Tubes / Valves 8 21st January 2008 01:31 AM
Question about Star Grounding voivodata Tubes / Valves 2 20th March 2007 07:46 PM
star grounding with a seperate PSu Rafal Chip Amps 6 29th October 2006 07:16 AM
Star Grounding Questions LHMAudio Solid State 5 12th May 2006 04:31 PM
Star grounding in PSU alexl Power Supplies 10 7th April 2005 08:46 PM


New To Site? Need Help?

All times are GMT. The time now is 08:00 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2