newbie with a choke question

xbartx · 24th February 2012, 10:33 PM

I would like to build a pre-amp. It would be my first build.
Looking on this site, I found this preamp build and looked like a good candidate.
12b4, 6ca4 build questions.... - AudioKarma.org Home Audio Stereo Discussion Forums

Looking through my parts supply, I found a choke and it has 3 leads, it was used in a power supply circuit.
All the references I come upon, the chokes have just 2 leads, can anyone explain the use of the 3rd lead.
Feel free to comment on my choice of
the 12b4 preamp as my first build.

Here is the schematic of that circuit
-Brad

dstockwell · 25th February 2012, 01:46 AM

This is your first build. I am by no means qualified, and am still looking at trying a first build, but this would scare the crap out me. There has got to be something more less intense than this.

xbartx · 25th February 2012, 02:08 AM

Quote:

Originally Posted by dstockwell

This is your first build. I am by no means qualified, and am still looking at trying a first build, but this would scare the crap out me. There has got to be something more less intense than this.

The schematic shown is not of the build, it is of the a tube receiver in which the choke came out of. I'm trying to learn how this choke with 3 leads differs than all the other chokes I see that only have 2 leads and if I can utilize it in my preamp.

astouffer · 25th February 2012, 04:11 AM

If it really is a center tap then you can either have a 7.5H or a 3.75H choke depending on how you connect it.

DF96 · 25th February 2012, 03:16 PM

No, a centre tap would give you a quarter of the total, not half. Inductance varies as turns squared.

xbartx · 25th February 2012, 06:59 PM

Quote:

Originally Posted by DF96

No, a centre tap would give you a quarter of the total, not half. Inductance varies as turns squared.

What would be the advantage over just using a 1.875H choke?

DF96 · 25th February 2012, 08:34 PM

That circuit is doing something more complicated, but I can't quite work out what. Maybe some form of hum cancellation?

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25th February 2012, 01:46 AM	#2
dstockwell diyAudio Member Join Date: Jul 2005 Location: Georgia	This is your first build. I am by no means qualified, and am still looking at trying a first build, but this would scare the crap out me. There has got to be something more less intense than this.

25th February 2012, 04:11 AM	#4
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	If it really is a center tap then you can either have a 7.5H or a 3.75H choke depending on how you connect it.

25th February 2012, 03:16 PM	#5
DF96 diyAudio Member Join Date: May 2007	No, a centre tap would give you a quarter of the total, not half. Inductance varies as turns squared.

25th February 2012, 08:34 PM	#7
DF96 diyAudio Member Join Date: May 2007	That circuit is doing something more complicated, but I can't quite work out what. Maybe some form of hum cancellation?