Ripple in unregulated supply for class-A amp - Page 2 - 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 11th October 2012, 01:52 PM   #11
agdr is offline agdr  United States
diyAudio Member
 
agdr's Avatar
 
Join Date: Sep 2010
I think the ferrite core on those will go into saturation if used in differential mode. Here is some info, 5th paragraph down:

Application Notes: How To Select And Use Ferrite/Nanocrystalline Common Mode Chokes : CWS Coil Winding Specialist, manufacturer of transformers, inductors, coils and chokes

But those CM chokes are cheap enough you could give it a try! Whatever impedance they wind up producing may be enough to do the job.

Another thought is just one 0.25 ohm 20W resistor between the two 40mF cap banks, rather than the 3 0.1Rs. The results are nearly as good.

Last edited by agdr; 11th October 2012 at 02:15 PM.
  Reply With Quote
Old 11th October 2012, 04:21 PM   #12
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
I'll be trying some of these common-mode chokes, a couple of these are already on they way to me. They're pretty cheap in any case. I'll see if they work, but I get it now that the core might indeed saturate in differential mode.

They Hammond chokes have too much DCR for my application, I would have to had planned for them from the start or to lower my power output as it stands.

If the CM chokes don't do it, I wonder if the primary or secondary winding of a small transformer might do?

IG
  Reply With Quote
Old 12th October 2012, 12:08 PM   #13
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
The common-mode donut chokes do seem to be saturating. They have some effect, but no where near what simulation predicts. Tiny power resistors do help out, but not enough on their own. It's kind of hard finding something that'll happily pass the 8 amperes required. The secondary winding of a small Hammond 166L24 transformer I have has under 1ohm DCR and I measured its inductance at ~43mH. This one worked really well and took down ripple to ~20mV. It was unfortunately on the fast track to heath-death and would not have lasted more than a few minutes IMO.

IG
  Reply With Quote
Old 12th October 2012, 01:44 PM   #14
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
try using a transformer out of a dead microwave oven.
Use the existing coils. take off the existing I of the EI and re-attach using paper as a gap filler in the EI.
You now have a gapped EI choke. and it cost you nothing.
Vary the gap to see what effect it has on inductance and saturation, if any.
__________________
regards Andrew T.
  Reply With Quote
Old 12th October 2012, 02:32 PM   #15
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
Quote:
Originally Posted by AndrewT View Post
try using a transformer out of a dead microwave oven.
Use the existing coils. take off the existing I of the EI and re-attach using paper as a gap filler in the EI.
You now have a gapped EI choke. and it cost you nothing.
Vary the gap to see what effect it has on inductance and saturation, if any.
That's where my thinking was leading me, large salvage transformers, microwave sounds good for this. I might have a couple of regular cheap power transfos to try first though.

~30mH and up might be good and DCR should stay below ~1.5 ohm.

IG
  Reply With Quote
Old 12th October 2012, 02:36 PM   #16
diyAudio Member
 
Join Date: Jan 2012
post 7 .......demeterart


+1
  Reply With Quote
Old 12th October 2012, 02:40 PM   #17
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
the two microwave oven transformers I have salvaged do not have interleaved laminations.
They have all the I's on one side. That makes them very easy to dismantle and just as easy to reassemble.
__________________
regards Andrew T.
  Reply With Quote
Old 12th October 2012, 02:57 PM   #18
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
Quote:
Originally Posted by epicyclic View Post
post 7 .......demeterart


+1
I might consider this down the road, but killing the hum at the source seems like a worthy first step IMO.

IG
  Reply With Quote
Old 12th October 2012, 03:06 PM   #19
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
CRC or CLC instead of C alone.

I always use the analogy of rCRC rather than omitting the leading r.

When you use C alone that missing r when replaced gives rC. You are using a filter with very little filtering effect due to the small r.

When you put in a real and useful R, the filter attenuates the hum much more.
__________________
regards Andrew T.
  Reply With Quote
Old 12th October 2012, 03:25 PM   #20
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
Quote:
Originally Posted by AndrewT View Post
CRC or CLC instead of C alone.

I always use the analogy of rCRC rather than omitting the leading r.

When you use C alone that missing r when replaced gives rC. You are using a filter with very little filtering effect due to the small r.

When you put in a real and useful R, the filter attenuates the hum much more.
I had some mild success with some CRC attempts around 1ohm last night. I also have burn marks on my fingers. 8 amperes is a lot for anything above 0.1ohm.

IG
  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
Unregulated power supply output impedance Navyblue Power Supplies 41 13th August 2012 04:20 AM
Unregulated Power Supply maxseeley Vendor's Bazaar 1 18th October 2011 06:41 PM
unregulated wallmart power supply cap size ash_dac Power Supplies 11 17th August 2005 11:39 PM
Using a dropping resistor in Zen V4 unregulated supply. G Pass Labs 3 30th October 2002 04:17 PM
Help with Zen v4 unregulated supply. G Pass Labs 2 23rd October 2002 02:10 PM


New To Site? Need Help?

All times are GMT. The time now is 05:14 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