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1st February 2007, 06:42 PM  #1 
diyAudio Member
Join Date: Sep 2006
Location: Graz, Austria

proper design of pifilter for Aleph 30
Hi folks!
When dimensioning the inductor vor this CLCfilter, how is it done properly? Here is a nice schematic, however it is for 180 000uF which is more than I want. I'm more interested in 3x 22 000uF caps, so the inductor would go between the first 2 caps I think. But how to calculate the proper inductor value? 3.9mH won't fit I think. Any ideas? Have fun! Hannes
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1st February 2007, 06:55 PM  #2 
The one and only

Any value will improve the noise, so just do the largest you
can. 
1st February 2007, 07:00 PM  #3 
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again............
http://www.duncanamps.com/psud2/index.html download it and play with read help to know more
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1st February 2007, 08:00 PM  #4 
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Location: quebec

in my aleph 3 68000uF+1.2mH +68000uF
with good result supply ripple = 25mv ac standard value are 2mH to 4mH but inductor has resistance air core = no saturation but maybe more resistance and heat and magnetic induction in your aleph i test my 1.2mH iron core for no saturation @ 10A wire=no 16 resistance=0,15 ohm 
2nd February 2007, 10:21 AM  #5 
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Join Date: Sep 2006
Location: Graz, Austria

Thanks for all replies!
Well. so is there no optimum value? Since capacitors cause a phase shift, I thought there's an optimum inductor value that shifts the phase of the remaining ripple perfectly back to 0°  which I guess should be the best. What makes me wonder is if it's only positive to use a CLC, why wasn't it used in the original Aleph30 or Pearl? When it's so nice, I'll add one also to the pearl of course, or is this just of academic value, because the fets contribute far more noise? Interesting subject! Thanks guys! Any input appreciated! Have fun! Hannes
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2nd February 2007, 11:01 AM  #6 
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"thought there's an optimum inductor"
in my book maybe yes? if you look CLC like C +LC for LC fc=1/(6.28 x squareroot( LC) ) for power 50hz ripple=100hz for power 60hz ripple=120hz fc with factor 5 to 10 of ripple hz is good optimum: 1too low L = no effect 2optimum is factor 5 to 10 3too big L = difficult to find with low R and R= voltage drop and heat 
2nd February 2007, 11:22 AM  #7 
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Location: Graz, Austria

Ok, I see what's the problem, you'll never get the inductors you would need.
So for a 3.9mH choke you would need just 26 Farads capacitance... Or for 66000 uF only 1.55 Henry inductance... So with what I could get, I'm just a factor 50 off what would be ideal. I see. So better get a 6.8mH inductor then. Have fun! Hannes PS: but why are inductors so rarely used then? Too expensive or less efficient than adding capacitance for the same money?
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2nd February 2007, 11:30 AM  #8 
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?????????
if L=3.9mH C=66000uF fc=9.92hz very good factor 10 and a little more if my calculator hp is rigth or me :) 
2nd February 2007, 11:34 AM  #9 
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Location: Graz, Austria

Ah ok I misunderstood you!
You mean fc times 510 to get the 100/120Hz ripple would be ideal! I see, thanks a lot for clarification! Why 510 times? Thanks a lot! Hannes
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2nd February 2007, 12:27 PM  #10 
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Location: quebec

why factor 10
thumb law :) for me factor 10 reduction of ripple is already very good to give a good step down on speaker hum factor 20 or 30 is better if and only if : 1big inductor with big wire for low R 2no magnetic saturation @ 10A (also thumb law) 3maybe the money talk also :) in my aleph 3 the factor is 6,8 with good 25mv ac ripple bye 
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