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Old 29th January 2008, 08:47 PM   #1
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Default Re-Gapping OPT

I have a pair of transformers that were gapped for 35mA of current. I am running them considerably lower than this (~18mA) and thought that a smaller gap might improve performance a tad. So, the questions is a) is this assumption correct, and if so b) how difficult is this to do, and is it even possible? Any tips/suggestions?
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Old 29th January 2008, 10:57 PM   #2
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Default Re: Re-Gapping OPT

Hi,

Quote:
Originally posted by dsavitsk
Any tips/suggestions?
Yes, don't.

The gap not only affects inductance at specified DC, but also LF saturation point. Sure, you'll get better low F3 performance, but you'll also significantly reduce the power handling capacity.

Cheers!
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Old 29th January 2008, 11:03 PM   #3
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I would think it is more likely to improve performance with more gap!
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Old 30th January 2008, 12:51 AM   #4
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hey-Hey!!!,
Power is a f'n of AC flux. AC properties are not related to gap( mostly ). Low frequency does care about inductance, so less gap can be a good thing there. Can it be done? Of course it can, though risk is not zero.
cheers,
Douglas
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Old 30th January 2008, 04:38 AM   #5
flg is offline flg  United States
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Quote:
Originally posted by Bandersnatch
hey-Hey... AC properties are not related to gap( mostly ). Low frequency does care about inductance, ...cheers,
Douglas
More gap will increase L Higher Load Z
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Old 30th January 2008, 08:53 AM   #6
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Quote:
Originally posted by flg


More gap will increase L Higher Load Z
More L with a wider gap? How you figure that
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Old 30th January 2008, 10:35 AM   #7
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Default Inductance and gap...

Nah....

An Increase in air-gap will Reduce Inductance and increase the current at which the core saturates, it will also increase the low freq response to a higher figure--Great if you want to make a guitar output Tx.....

The reverse is true, but we are talking about gaps in the order of 0.1mm to 0.2mm Total gap--Meaning 0.05 to 0.1mm thickness 'paper' sheet as the spacer Mag field passes gap twice don't forget And it reduces the current at which the core saturates. If its a high grade core the core distortion appears rather suddenly as the point of saturation is reached ....

If your Tx is rated at say 50mA and your'e running at 35mA, Dont even think of messing with it--It is quite a precision item.--. Its just not worth the effort unless you have graded 'shims' below 0.05mm and some way of installing them to ensure all the laminations are 'butted' up correctly to the shims, and a Good Inductance measurement device to see what effect the alteration has made--Having made a few O/P Tx, I can say that 'setting the gap' is the very hardest part-- Especially when your'e needing a matched pair of Tx.........

Check out Yvesm Tx design proggie, Interesting to experiment with the gap, the coil winding/interleave numbers and core sizes and materials in there,-- Be easier to strike a new Tx from the data you can get using this great little proggie--Used it many times for various experiments/Tx design and chokes etc....
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Old 30th January 2008, 06:28 PM   #8
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Default Re: Inductance and gap...

Quote:
Originally posted by Alastair E
Its just not worth the effort unless you have graded 'shims' below 0.05mm and some way of installing them to ensure all the laminations are 'butted' up correctly to the shims, and a Good Inductance measurement device to see what effect the alteration has made-
Seems like a reasonable warning to me. Thanks.
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Old 30th January 2008, 09:41 PM   #9
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Default Setting gaps

Couldn't one come up with a jig that has a micrometer assembly that would slide the E I laminations apart or together using Teflon strips between the laminations?
_______________________________________Rick....... .....
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Old 30th January 2008, 09:52 PM   #10
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Teflon is probably too squishy. Dave Slagle at Intact Audio has settled on the thickness of a Post-It Note as a standard for gap setting.

http://www.intactaudio.com/forum/viewtopic.php?t=5
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