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Old 30th November 2012, 12:10 PM   #21
diyAudio Member
 
Join Date: Feb 2010
Location: Athens Greece
Quote:
Originally Posted by dave slagle View Post
I have seen this said before but I have never been able to see it in practice except when the applied DC shrinks the physical gap.

dave
Dave,
bass performance is a result of magnetics. Trebble performance is a result of coil winding. It is so simple! DC bias excites the core, raising the effective permeability, so bass is better. Logical, isn't it?
Here there is no chance of gap shrinking, it is made of very stiff carton paper. Gap must be absolutely stable in thickness.

Greetings,
Peter
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Old 30th November 2012, 12:38 PM   #22
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Location: NYC
Quote:
Originally Posted by petavgeris View Post
Dave,
bass performance is a result of magnetics. Trebble performance is a result of coil winding. It is so simple! DC bias excites the core, raising the effective permeability, so bass is better. Logical, isn't it
Greetings,
Peter
Hey,

Can you point me to one measured or documented result where this happens? Every inductance vs current curve that I have measured (or seen) always starts with inductance being the greatest at 0 DC current and the addition of DC current reduces the inductance.

dave
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Old 30th November 2012, 05:19 PM   #23
JZatopa is offline JZatopa  United States
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Location: Chicago
Thanks for sharing petavgeris. When you post more pics, could you post one with the transformer next to a can of coke, it is hard to visualize the size of the transformers in your pictures.

Considering the work and documentation you have created, are you planing on selling these on a custom order basis? If so, what price range are you looking at?
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Old 30th November 2012, 05:35 PM   #24
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Quote:
Originally Posted by dave slagle View Post
Hey,

Can you point me to one measured or documented result where this happens? Every inductance vs current curve that I have measured (or seen) always starts with inductance being the greatest at 0 DC current and the addition of DC current reduces the inductance.

dave
Exactly the opposite!
Inductance (all else being equal or unchanged) is related to the square of primary turns and the magnetic permeability. Permeability mu=B/H. The gap reduces permeability, so we have the effective permeability of the whole structure including the gap.
Study all B-H charts, they are more or less the same.
We first have initial permeability, then incremental permeability, then maximum permeability and beyond this level permeability starts to get smaller till saturation where it is zero.
I am really impressed that you have never seen any chart like this... Whatever I have measured simply justifies one of the most principal laws of magnetism. With little excitation you get sybstantially increased inductance!

Regards,
Peter

Last edited by petavgeris; 30th November 2012 at 05:41 PM.
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Old 30th November 2012, 06:13 PM   #25
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Quote:
Originally Posted by petavgeris View Post
Exactly the opposite!
Inductance (all else being equal or unchanged) is related to the square of primary turns and the magnetic permeability. Permeability mu=B/H. The gap reduces permeability, so we have the effective permeability of the whole structure including the gap.
agreed

Quote:
Study all B-H charts, they are more or less the same.
yes.

Quote:
We first have initial permeability, then incremental permeability, then maximum permeability and beyond this level permeability starts to get smaller till saturation where it is zero.
here is where you go off track.
Initial and maximum permeability are AC functions. Incremental permeability is an ac function with an imposed DC field.

At no point does imposing a DC field increase permeability.

Quote:
I am really impressed that you have never seen any chart like this...
I have... in many different forms.

Quote:
Whatever I have measured simply justifies one of the most principal laws of magnetism. With little excitation you get sybstantially increased inductance!
that is true for AC excitation. in the case of DC bias just the opposite happens. (inductance decreases)

dave
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Old 1st December 2012, 12:54 PM   #26
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I have a graph somewhere.
With a gap and DC bias there is an initial substantial increase in mu, then mu is almost dead flat and then it starts to go down due to saturation. That's one of the main virtues of SET amps. Push Pull gives terrible sound compared to Single Ended because there is no DC bias and initial effective permeability of iron is quite low, so low level detail gets lost. It is this low level detail where magic of music lies! This has nothing to do with the amplitude of the signal, it is purely a function of DC bias. Gap and DC is all the magic of SET amps!
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Old 1st December 2012, 01:08 PM   #27
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Location: Athens Greece
Quote:
Originally Posted by DJNUBZ View Post
Thanks for sharing petavgeris. When you post more pics, could you post one with the transformer next to a can of coke, it is hard to visualize the size of the transformers in your pictures.

Considering the work and documentation you have created, are you planing on selling these on a custom order basis? If so, what price range are you looking at?
Hello!
Yes, by all means. The amp chassis are now at the workshop and they're almost done! I hope that by next week I will post the pictures of this rather insane project. You will see one of the most exotic power amps ever made, if not the most exotic one!

I hope information mentioned in the first text is quite descriptive, including the dimensions.

Regarding any custom orders, for your information I can wind any transformer anybody might ever think of. I have already done it many times for local audiophiles and friends. I am mostly involved in custom order projects that are beyond levels of mainstream performance. This pair consists of four o rings in form of cut cores, ideal for a double c core stereo set. As soon as they were not needed, I decided to wind one pair of the best 3.5kOhms trannies that I could dream of, just for the one and only person that would like to acquire them.

I plan to sell them sometime in the near future for EUR 2.5k, with complete documentation, secondary connection instructions, full set of gapping material and lifelong support.

This is my last set of 0.1 and 0.23 millimeters cores of 10 sq. cm cross sectional area(32x32mm). I have several 0.1mm and 0.23mm cores in 6.25 sq cm cross sectional area (25x25mm), ideal for power amps of up to 5W SET OPTs. I plan to wind a pair of OPTs for 2A3 and a pair for type 45 tubes.

Thanks for your feedback.
Regards,
Peter
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Old 1st December 2012, 01:14 PM   #28
tinitus is offline tinitus  Europe
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sorry, Im not gonna mess with you pros here, but this sounds like its got something to do with one of Joe Rasmussens's transformer 'experiments'

I think he attached some kind of DC curcuit to keep the core saturation constant
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Old 1st December 2012, 02:49 PM   #29
Tyimo is offline Tyimo  Hungary
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Hi Petavgeris!
Thanks. I am also very "satisfied" with the quality of women here, but not with the quality of iron cores....

greets:
Tyimo
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Old 1st December 2012, 03:11 PM   #30
cab is offline cab
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what is a cnc laser jet cutter?
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