Ground Loop problem - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

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
Reply
 
Thread Tools Search this Thread
Old 28th April 2006, 02:33 AM   #1
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
Default Ground Loop problem

Can any one suggest me some ideas / techniques for making some ground loops disappear. I have a stereo mon-block that a friend has built. It is a class a Mini a Both channels share a single CRC psu with a 300Va transformer. I have tried every thing I could possibly think of. When I connect a audio source via RCA it has a hum a low hum possible a ac ground.

I have connected my ipod to see if it was the source but it was not because I have tried many sources. IF I unplug one channel left/right input the hum goes away and it is dead quiet. I have tested the ac ripple on the dc psu and there is ripple there but my mini as that I have have the same amount of ac ripple on it. I seriously cant think of any thing to do with this thing any more.. I have access to a scope. Can any one suggest any ideas ? I can post pics if needed.

Things I have tried

Replaced the input rca jacks
Twisted cables for rca and speaker terminal
Put a copper piece of metal around the transformer
Put a thermister on the ac input ground
  Reply With Quote
Old 28th April 2006, 06:05 AM   #2
Mad_K is offline Mad_K  Norway
diyAudio Member
 
Mad_K's Avatar
 
Join Date: Sep 2002
Location: Norway
Post that pic, also it might be a good idea to draw a gound map
__________________
Mads K
  Reply With Quote
Old 28th April 2006, 06:20 AM   #3
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
Here is a picture of the psu board.

It is setup as CRC with 3.oOhm resistors @ watt each.


Click the image to open in full size.
  Reply With Quote
Old 28th April 2006, 06:26 AM   #4
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
Here is a pic of the amp inside. I have the rca's mounted directly to the amplifier like how i had mine.. I still get the ground loop problem.
Attached Images
File Type: jpg scotty.jpg (92.1 KB, 634 views)
  Reply With Quote
Old 28th April 2006, 06:30 AM   #5
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
Here is the amplifier board. It only has 2 fets on the output stage.
Attached Images
File Type: jpg minia.jpg (83.7 KB, 478 views)
  Reply With Quote
Old 28th April 2006, 06:43 AM   #6
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
And here is a link to my crappy drawing to how it is all connected.


http://jleaman.ath.cx/aleph/testing-psusm.jpg
  Reply With Quote
Old 28th April 2006, 06:53 AM   #7
diyAudio Member
 
Andypairo's Avatar
 
Join Date: Sep 2002
Location: near Milano , Italy
In my (former) Aleph30 all the gnds (input and output) are taken from a star point at the power supply. This star point is connected with a single wire to the gnd of the boards.

Cheers

Andrea
__________________
I don't believe in audiophile components - except when I can get them at frugal-phile(tm) prices
  Reply With Quote
Old 28th April 2006, 06:59 AM   #8
jleaman is offline jleaman  Belgium
Banned
 
Join Date: Apr 2002
Send a message via AIM to jleaman
So, All the input and speaker grounds go to the same point ? Right where the dc is connected on the ps going to the main amplifier boards ?
  Reply With Quote
Old 28th April 2006, 07:10 AM   #9
diyAudio Member
 
Andypairo's Avatar
 
Join Date: Sep 2002
Location: near Milano , Italy
That's indeed the idea.

If you want to use a shielded wire for inputs just connect the shield to one side only.

Cheers

Andrea
__________________
I don't believe in audiophile components - except when I can get them at frugal-phile(tm) prices
  Reply With Quote
Old 28th April 2006, 08:40 AM   #10
Mad_K is offline Mad_K  Norway
diyAudio Member
 
Mad_K's Avatar
 
Join Date: Sep 2002
Location: Norway
Are you using R0? What value?
__________________
Mads K
  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
ground loop buzz problem SCOTT123 Solid State 3 24th March 2008 09:53 AM
hum,ground loop,earth loop problem with your answers please frank2395 Pass Labs 2 17th May 2005 06:46 PM
Ground loop problem in DIY pre-amp pfn Car Audio 4 28th November 2004 05:16 PM
Ground loop problem for sub? AudioIsFun Multi-Way 5 29th February 2004 07:14 AM
Leach Amp: Ground loop problem swede Solid State 7 15th May 2002 06:19 PM


New To Site? Need Help?

All times are GMT. The time now is 04:16 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