Common-mode EI PS Chokes - Page 2

rdf · 14th November 2006, 03:46 AM

I can't disagree with the details Dave but don't see how that makes them worse than single-ended chokes which typically don't make it past the audio band either and are useless for RF filtering. Add to that the large size (and cost + shipping cost) required to avoid core saturation and I can't help think CM will do the job better and easier for less.

BTW, I like the 'couple hundred mH' idea too. Just can't see how to achieve low ripple without hundreds of uF to go with it. Gets really expensive wrapped around an 813.

jayme, which Lundahl iron did you mean? All I see it audio stuff with pretty high DCR.

jarthel · 14th November 2006, 04:02 AM

Quote:

Originally posted by rdf

jayme, which Lundahl iron did you mean? All I see it audio stuff with pretty high DCR.

http://www.lundahl.se/pdfs/datash/1638.pdf

10H 36ohms(is this low enough?)

rdf · 14th November 2006, 05:06 AM

Thanks. Now why didn't I think to check under TRANSFORMERS for chokes?

ErikdeBest · 14th November 2006, 07:31 AM

Hi Dave Cigna

That's a long and nice explanation, although I must admit I don't understand everything.

But I see part of your point...the fact people are using power toroids as OPT in PP amps is because the inductance is high enough for proper power at audio frequencies. In PS's the choke should eliminate HF stuff, then I don't know how well a toroid would work, ie, how much inductance is left...but I read the capacitance between windings is pretty low in a power toroid, compared to a power EI trafo. Hm...the inductance for a standard Hammond choke is specified at which frequency?

I just bought 6x toroidals with 2x 115V primaries and 2x12V secondaries. I am planning a small amp ala "baby huey" using PL84 tubes for my hobby room: two of the toroids back to back for filaments and HV, two as OPT and two are left...but could be used as common mode choke. B+ would be around 250VDC. But that project won't start now, as I still have other ones to conclude first.

Erik

ErikdeBest · 17th June 2007, 08:36 AM

Hi George

Have you conducted any further test with common mode chokes?

Erik

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14th November 2006, 03:46 AM	#11
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	I can't disagree with the details Dave but don't see how that makes them worse than single-ended chokes which typically don't make it past the audio band either and are useless for RF filtering. Add to that the large size (and cost + shipping cost) required to avoid core saturation and I can't help think CM will do the job better and easier for less. BTW, I like the 'couple hundred mH' idea too. Just can't see how to achieve low ripple without hundreds of uF to go with it. Gets really expensive wrapped around an 813. jayme, which Lundahl iron did you mean? All I see it audio stuff with pretty high DCR.

14th November 2006, 05:06 AM	#13
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	Thanks. Now why didn't I think to check under TRANSFORMERS for chokes?

14th November 2006, 07:31 AM	#14
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Hi Dave Cigna That's a long and nice explanation, although I must admit I don't understand everything. But I see part of your point...the fact people are using power toroids as OPT in PP amps is because the inductance is high enough for proper power at audio frequencies. In PS's the choke should eliminate HF stuff, then I don't know how well a toroid would work, ie, how much inductance is left...but I read the capacitance between windings is pretty low in a power toroid, compared to a power EI trafo. Hm...the inductance for a standard Hammond choke is specified at which frequency? I just bought 6x toroidals with 2x 115V primaries and 2x12V secondaries. I am planning a small amp ala "baby huey" using PL84 tubes for my hobby room: two of the toroids back to back for filaments and HV, two as OPT and two are left...but could be used as common mode choke. B+ would be around 250VDC. But that project won't start now, as I still have other ones to conclude first. Erik

17th June 2007, 08:36 AM	#15
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Hi George Have you conducted any further test with common mode chokes? Erik

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