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Old 6th February 2003, 02:18 AM   #61
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Default Re: Choked

Quote:
Originally posted by James D.
Tony,

I asked my engineers at work to measure one for me...Not sure I believe the result as it quite good, although it is inline with Joel's result... I'll ask them to show me how they measured it later.

Results :

Inductance: 143H
Resistance: 3860R
Capacitance: 78pF.

I'm using them as plate and grid chokes in an ECL82 SE amp. Before it was a standard plate resistor and capacitor coupled design. It opened up the sound and made the bass more tuneful - maybe a bit deeper as well.

hope this helps

James

Thanks James, it give us a good look into these chokes.

What amazed me is the low capacitance for such a high # of turns.

By any chance can you see through the end of the outer insulation as how many layers of insulation this might have or if it looks like a perfect lay with insulation on each leyer?
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Old 6th February 2003, 05:06 AM   #62
GaryW is online now GaryW  United States
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Just catching this forum... A little bad juju on this thread. The 156c specs were posted on the audioasylum forum a while back: 156c data

The capacitance was likely measured at dc or close to. It's a bit higher at higher frequencies...

Gary
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Old 6th February 2003, 07:15 AM   #63
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Just checked with my chaps and the figures I posted were measured at:

Inductance: 143H @ 50Hz
Resistance: 3860R @dc
Capacitance: 78pF @ 1KHz.

Applied signals at 10V rms.

Thanks for posting the 'asylum' link - thats much better data...

ciao

James
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Old 12th February 2003, 07:32 PM   #64
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I'm kinda jumping in late on this thred but here is an observation I have from when I built my first version of the 26 line stage. For the plate load I used 2 156C's in series. They are cheap enough!

If I remember the numbers correctly (was 2 years ago) the -3dB points at both ends of the frequency range moved out. The LF -3dB point moved from 15hz to 7hz and the HF -3dB point moved from 30K to 90K.

The lower frequency increases as the inductance is doubled, the upper frequency increases as the capacitance of the chokes is in series and is roughly half that of a single choke.

The reason for the upper moving so much is like marketing numbers.... With the 156C's there was a dip at 50Khz then the response rose at 70K where the self resonance was at, then droped again. With one choke the dip at 50K was -4dB, With 2 chokes in series the dip was only -2dB.

Another cool trick that can be done using 2 chokes in series- if you stack the chokes and wire them correctly they become a hum bucking choke. Using my Weller soldering station as a magnetic signal source 2' from the chokes, when one choke was flipped upside down there was a 20dB reduction in received hum.

I mounted the chokes on standoffs that were the same height as the chokes with the chokes bottom to bottom. To see a picture of the double choke install look in the images section of my webpage. The one with the chokes is "26 preamp bottom side"

Hope this rambling is of some use...
Gary
http://home.pacifier.com/~gpimm/
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Old 12th February 2003, 07:52 PM   #65
Joel is offline Joel  United States
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Gary,
Very interesting. Thanks for the link! But, where are the schematics for all those amps? You're just teasing the reader...

How do you like your 30/31 amp? I'm building a 31 push-pull right now, with #30's for gain duty. Phase splitter will be the Hammond 124B, when I get around to ordering one.

Yes, not enough has been said about paralleling chokes! It seems like a near perfect solution to any frequency response concerns, no? The only drawback is the increased DCR.

Joel
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Old 12th February 2003, 08:18 PM   #66
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Default IN SERIES.

Hi Joel,

Quote:
Yes, not enough has been said about paralleling chokes!
Just a little lapsus linguae I presume?

Cheers,
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Old 12th February 2003, 08:34 PM   #67
Joel is offline Joel  United States
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I meant "chokes in series". Sorry.
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Old 12th February 2003, 08:59 PM   #68
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Hi Joel,

All the schematics, with the exception of the David and my new all active loaded, teflon coupled, transformer output phono stage can be found in the schematics section of my web page.

Gary
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Old 14th February 2003, 12:40 AM   #69
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Default PHONO STAGE.

Hi,

Quote:
David and my new all active loaded, teflon coupled, transformer output phono stage can be found in the schematics section of my web page.
Having visited your website once again today, I must admit I can't wait for that phono stage...I was, still am thinking of building a fully balanced phono stage using CCSs and such.

Thanks for sharing Gary,
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