F5 Ground Loop - Need Ideas.. - Page 6 - 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 10th May 2013, 02:09 PM   #51
diyAudio Member
 
jneutron's Avatar
 
Join Date: Jan 2004
Location: away
Quote:
Originally Posted by madisonroberts View Post
Now I am now worried about oscillation. I didn't know twisting output wires together would be the right thing to do. I have read to only twist the inputs.. V- and V+ are tied together with zip ties, but not twisted..

Are these concerns related to oscillation? I am worried about my speakers now. Not that they are humming but that they might EXPLODE or something..
Yes, they also relate to oscillation. It is always best to twist together conductors which carry current to and from two objects, so that the fields are constrained as much as possible. Supply rails and transformer primaries are not immune to this.

I added to my previous post, you may wish to re-read it.

I'd worry only if your heatsinks were still getting hot. If it's oscillating, either look with a scope or substitute an 1/8th watt 8 ohm resistor at the far end of the speaker cables as a sacrificial lamb so to speak. If your speakers are in harms way, that resistor will toast.

jn
  Reply With Quote
Old 10th May 2013, 03:03 PM   #52
diyAudio Member
 
Join Date: Feb 2012
Ok, I will go back in a twist the wires together that you recommended.

I will also borrow a friends scope and check the waveforms on output.

Of course, the heatsinks get hot just like every other F5. I just have no way of knowing what temp is too hot. Maybe I am overreacting. I mean, they arent too hot to touch or anything. I mean, I can put my face or hands on the sinks indefinately without too much discomfort whatsoever. I will look for a temperature gauge to check this out more precisely.

Are there any tests I can perform to troubleshoot the possibility of oscillation? Shorting inputs, etc..?
  Reply With Quote
Old 10th May 2013, 03:20 PM   #53
basi is offline basi  Croatia
diyAudio Member
 
Join Date: Aug 2007
Location: Novska
Quote:
Originally Posted by jneutron View Post
Basi,

The troublesome aspect of this is the drawing puts the speaker ground current in close proximity to the input ground. Coupling between them can cause oscillation.

jn
No if they are connected like a drawn in post 24.

Greetings!!!
__________________
Marantz rules
  Reply With Quote
Old 10th May 2013, 03:36 PM   #54
diyAudio Member
 
jneutron's Avatar
 
Join Date: Jan 2004
Location: away
Quote:
Originally Posted by madisonroberts View Post
Ok, I will go back in a twist the wires together that you recommended.

I will also borrow a friends scope and check the waveforms on output.



Of course, the heatsinks get hot just like every other F5. I just have no way of knowing what temp is too hot.

Are there any tests I can perform to troubleshoot the possibility of oscillation? Shorting inputs, etc..?
Scope is best.

From your earlier post, I thought your sinks were getting hotter after a mod. That is why I was thinking osc.

Quote:
Originally Posted by basi View Post
No if they are connected like a drawn in post 24.

Greetings!!!
24 is indeed a bit better. Note however, that the output wires are not twisted around the ground. That loop can induce into the input ground loop.

Remember, even though the input pair is twisted, they will still form a ground loop with the other pair at the preamp. That entire loop will be sensitive to broadcasted magnetic fields.

jn
  Reply With Quote
Old 10th May 2013, 04:00 PM   #55
basi is offline basi  Croatia
diyAudio Member
 
Join Date: Aug 2007
Location: Novska
Quote:
Originally Posted by jneutron View Post
Scope is best.



24 is indeed a bit better. Note however, that the output wires are not twisted around the ground. That loop can induce into the input ground loop.

Remember, even though the input pair is twisted, they will still form a ground loop with the other pair at the preamp. That entire loop will be sensitive to broadcasted magnetic fields.

jn
Yes i agree Output wires must be twisted and away from input like power wires.
I was only draw basic star ground sheme to help madisonroberts to resolve ground loops.There is many more tricks in audio design but that is not the question in this thread.I'm very pleased that madisonroberts resolve the problem and learn in the way.

Sorry for bad English.

Greeatings!!!
__________________
Marantz rules
  Reply With Quote
Old 10th May 2013, 04:04 PM   #56
omishra is offline omishra  India
diyAudio Member
 
Join Date: Nov 2008
Location: PNQ, MH
@basi, no problem. Your intention is appreciated.
Regards.
  Reply With Quote
Old 10th May 2013, 05:05 PM   #57
diyAudio Member
 
Join Date: Feb 2012
What I really need to do is get a thermometer and get an exact temperature reading. They sinks do feel hotter (i think) and they seem to be getting hotter faster. Although, It could be that I was not paying as much attention before this mod.

I will go in and twist the output wires as well as the AC wires to the barrier strip.

Hum is gone, I am a very happy camper.

Thanks everyone for your help!! I will keep this thread updated with anything related to my former problem.

Regards
  Reply With Quote
Old 10th May 2013, 05:26 PM   #58
diyAudio Member
 
jneutron's Avatar
 
Join Date: Jan 2004
Location: away
Quote:
Originally Posted by basi View Post
Yes i agree Output wires must be twisted and away from input like power wires.
I was only draw basic star ground sheme to help madisonroberts to resolve ground loops.There is many more tricks in audio design but that is not the question in this thread.I'm very pleased that madisonroberts resolve the problem and learn in the way.

Sorry for bad English.

Greeatings!!!
Your english was clearly up to the task, as it certainly helped madisonroberts..

Good job.

jn
  Reply With Quote
Old 10th May 2013, 08:16 PM   #59
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Leave the amp on for 1/2 hour.

Then touch the heatsinks and report back how long you can touch them without it being uncomfortable.

If it's longer than 5 seconds, you are fine, if close, probably OK.
  Reply With Quote
Old 11th May 2013, 08:26 AM   #60
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
post40
Quote:
Originally Posted by madisonroberts View Post
Ok here are some photos of my new isolated Main Audio (Star) Ground. It is isolated from chassis using nylon screw and nuts. All connections are in contact with each other, but are not in contact with the chassis. Main audio ground is connected to Chassis/Safety Earth via CL-60 thermistor.

The last two photos are of my grounded grid preamplifier. There is a ground bus wire connecting all the RCA jack grounds. This ground bus is connected to Chassis/Safety Earth via a small 1/4 watt resistor.
The last pic shows all those Hot wires without the corresponding Return wire, for maximisation of Loop Area.
__________________
regards Andrew T.

Last edited by AndrewT; 11th May 2013 at 08:33 AM.
  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 Jamh Chip Amps 10 2nd November 2007 07:18 PM
Fix a ground loop! sorenj07 Digital Source 2 1st October 2007 06:39 AM
hum,ground loop,earth loop problem with your answers please frank2395 Pass Labs 2 17th May 2005 06:46 PM
Buzzing, could it be a ground loop? JoeBob Tubes / Valves 3 14th July 2003 02:24 AM
does connecting mains ground with circuit ground create a ground loop? jarthel Everything Else 0 25th June 2003 12:55 PM


New To Site? Need Help?

All times are GMT. The time now is 04:49 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