Unusual filtering scheme question - 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 4th March 2013, 02:02 PM   #1
diyAudio Member
 
Join Date: Mar 2012
Location: New York
Default Unusual filtering scheme question

I found this decent commentary on solid state amplifier power supplies, but the final 680nF capacitor has a 1 ohm, 17w resistor in series with it.

I understand the liberal reservoir capacity he favors, but I have never seen this before, and why such high wattage resistor when the ripple should be miniscule and only 120Hz.?

Solid State Power Amplifier Supply Part 3
  Reply With Quote
Old 4th March 2013, 02:13 PM   #2
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
I understand the use of a zobel to damp hf noise and junk, but 17W indeed seems overkill.
Also his statement "... to get rid of the capacitor inductance" is incorrect - he merely puts a resistor in series with the capcitor inductance. It would still be advised to use a low-inductance capacitor for best filtering results.

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 4th March 2013, 02:17 PM   #3
diyAudio Member
 
Join Date: Mar 2012
Location: New York
Thanks jan. Are the "orange drops" considered low inductance--for this purpose?

And yes, I took his comment as this filter section taking the inductance out of the main cap bank.

Last edited by ITPhoenix; 4th March 2013 at 02:30 PM. Reason: fogot qualification
  Reply With Quote
Old 4th March 2013, 03:59 PM   #4
diyAudio Member
 
Join Date: May 2011
Location: Silicon Valley
Quote:
Originally Posted by jan.didden View Post
Also his statement "... to get rid of the capacitor inductance" is incorrect - he merely puts a resistor in series with the capcitor inductance.
Jan, I suspect that he is referring to the inductance of the massive 20,000 uF capacitors upstream. I suspect the (1 ohm + 680 nF) zobel network is an attempt to build a snubber that forms the "R" part of a damped RLC circuit; where L is the inductance of the 20,000 uF filter caps (and their wiring!), and C is the capacitance of those same 20,000 uF caps. I suspect that he calculates the "characteristic impedance" of the LC circuit Z = sqrt(L/C) and finds this to be around 1 ohm.
  Reply With Quote
Old 4th March 2013, 04:09 PM   #5
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
He may be trying to damp the parallel resonance he has created by bypassing the big caps. I note that his circuit description is long on words and short on numbers. This can sometimes be a warning sign that no actual design has taken place, merely an assembling of 'rules of thumb' or personal preferences.
  Reply With Quote
Old 4th March 2013, 04:26 PM   #6
diyAudio Member
 
Join Date: Jul 2011
Location: Canary islands
Hi ITPhoenix

I usually put a zobel/snubber on transformer secondary side too ( before diods bridge )
And yes, TNT values look on the hight side....may 330nf+1R/5w will damp well ringing.

What do you mean for "orange drops" ? tantalum ?

Ciao

Marco
  Reply With Quote
Old 4th March 2013, 07:09 PM   #7
diyAudio Member
 
Join Date: Mar 2012
Location: New York
Sprague polypropelenes are coined "orange drops" due to their color and shape. Prefered my musicians in guitars and amps for their supposedly better tone and lower noise. They are slightly more expensive than average films.

In the diagram it appears there is a transformer primary snubber. 220nF in series with possibly 9R1. Too fuzzy; cannot verify resistor value.

Last edited by ITPhoenix; 4th March 2013 at 07:14 PM.
  Reply With Quote
Old 4th March 2013, 07:24 PM   #8
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by transistormarkj View Post
Jan, I suspect that he is referring to the inductance of the massive 20,000 uF capacitors upstream. I suspect the (1 ohm + 680 nF) zobel network is an attempt to build a snubber that forms the "R" part of a damped RLC circuit; where L is the inductance of the 20,000 uF filter caps (and their wiring!), and C is the capacitance of those same 20,000 uF caps. I suspect that he calculates the "characteristic impedance" of the LC circuit Z = sqrt(L/C) and finds this to be around 1 ohm.
I suspect not
There's also the non-ideal coupling between the primary and secondary which will make all this not very sensible. You'd have at least the leakage inductance between the prim and sec which probably is much higher that the cap inductance in the first place.

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 4th March 2013, 07:26 PM   #9
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by DF96 View Post
He may be trying to damp the parallel resonance he has created by bypassing the big caps. I note that his circuit description is long on words and short on numbers. This can sometimes be a warning sign that no actual design has taken place, merely an assembling of 'rules of thumb' or personal preferences.
... or 'everyone knows' as found online

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 4th March 2013, 07:27 PM   #10
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by bicefalo View Post
Hi ITPhoenix

I usually put a zobel/snubber on transformer secondary side too ( before diods bridge )
This is very sensible!

jan
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  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
unusual passive x-over question amp88 Parts 7 9th November 2010 12:43 PM
Baffle step Question for unusual enclosure REM Multi-Way 4 18th August 2007 07:31 PM
Regulating tube amp power supply - can Iget away with a simpler CLC filtering scheme? zobsky Tubes / Valves 0 12th October 2006 04:10 AM
AC Filtering question HIPCHECK Power Supplies 13 4th October 2006 04:02 PM
AC mains filtering question thylantyr Solid State 4 26th March 2003 08:28 PM


New To Site? Need Help?

All times are GMT. The time now is 12:58 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