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Old 24th February 2012, 11:33 PM   #1
xbartx is offline xbartx  United States
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Default newbie with a choke question

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


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Old 25th February 2012, 02:46 AM   #2
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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.
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Old 25th February 2012, 03:08 AM   #3
xbartx is offline xbartx  United States
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Quote:
Originally Posted by dstockwell View Post
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.
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Old 25th February 2012, 05:11 AM   #4
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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.
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Old 25th February 2012, 04:16 PM   #5
DF96 is offline DF96  England
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No, a centre tap would give you a quarter of the total, not half. Inductance varies as turns squared.
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Old 25th February 2012, 07:59 PM   #6
xbartx is offline xbartx  United States
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Quote:
Originally Posted by DF96 View Post
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?
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Old 25th February 2012, 09:34 PM   #7
DF96 is offline DF96  England
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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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