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Old 19th March 2006, 03:34 PM   #1
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Default Pro and cons high DCR filter choke

Hello,

I have several 30H (or maybe more - my inductance meter measures up to 30H only) 65mA 1550ohm chokes from old junk field-coil speakers. They look like a round bobbin with cylinder core mounted in metal C-shaped frame (will post a picture later).

I would like to use them in several pre-amp and headphone amp designs (up to 65mA) in PSU choke input filters but I am little bit scared of their high DCR.

I read many articles re high DCR and many people said it could increase the resistance of the supply line with all negative aspects to the sound. Despite of that Duncan PSU designer reports very good results due to their high Q factor.

Could you please share your practical opinions re high DCR choke issue in SE class A designs?
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Old 19th March 2006, 09:15 PM   #2
Tweeker is offline Tweeker  United States
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Regulation isnt an issue with SE class A, but you need good capacitors in a high impedance supply as the supply depends more on them to draw from.

Preamps are often using straight RC sections, so higher resistance might be ok here.
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Old 20th March 2006, 01:31 AM   #3
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What Tweeker says. You don't need to be concerned about DCR of a couple of k unless the demand on the power supply is variable, e.g. a class AB1 power amp.
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Old 20th March 2006, 03:42 AM   #4
lndm is offline lndm  Australia
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I have not seen it explained better than Voltsecond did on his site.

http://www.siteswithstyle.com/VoltSe...C_ringing.html

http://www.siteswithstyle.com/VoltSe...LC_TANK_Q.html

These will help you design a neutral power supply. (Long but worth it).
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Old 20th March 2006, 07:51 AM   #5
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Thanks for the inputs and for the useful links.

It seems to be true that high DCR chokes waste low frequency power. When the DCR increases, the Q decreases and vise versa in spite of the fact the high DCR could provide better damping and is less prone to ringing.
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Old 20th March 2006, 04:29 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

you could regard using a high DCR choke as a
combination of choke and resistive filtering.

As CRC filtering is a good thing for low power
class A circuits (constant current from supply),
at low/medium power it should be fine.

/sreten.
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Old 20th March 2006, 08:24 PM   #7
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This made me think about the experiments made by the dutch DHTrob (www.dhtrob.com) based on steve bench's work. (Speaking about it, I believe more in the work of steve bench than that of dhtrob. Steve is more the engineer, while dhtrob is truly high-ender) Well, they both worked it out, and maybe you get some inspiration. Dhtrob says he is using it for his preamp.

The original, made by steve bench
http://members.aol.com/sbench/norchv.html
http://members.aol.com/sbench/reg5.html

DHTrob applied this for a power supply for his preamp.
http://www.dhtrob.com/projecten/voeding_vr_tubes_1.htm

the whole article is in dutch, but you can see the schematics throughout. His final schematic is shown here
http://www.dhtrob.com/projecten/afbe...g_vr_tubes.GIF

I am sure you can make something very similar with your chokes. (I would love to have some of those...I have a lot of OB2 wanting some use)
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