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Old 9th January 2013, 01:35 PM   #41
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Quote:
Originally Posted by WrineX View Post
Wow thx for the so long rePly and help , so in the end , they suck well at least a good reason to buy some new ones Gina take a look second hand first
Have you check the bias or have you not??
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Old 9th January 2013, 02:40 PM   #42
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Originally Posted by Elvee View Post
Before jumping to conclusions, you should confirm the core material is actually the cause of your problems, otherwise you could spend money for nothing
Hello Elvee,
Is this the test you propose? (see attachment)

1) With switch open, adjust the output of the preamplifier to a low level that produces audible distortion in the ESL.
2) Close switch to add/mix in a high amplitude ultrasonic signal with the audio going to the power amp.
3) As the amplitude of the ultrasonic signal is increased, the amount of core distortion should decrease resulting in less audio distortion heard in the ESL.


@alexberg,
WrineX has tried several power amplifiers with identical results.
It seems unlikely that all of his power amplifiers have DC offset problems.
.
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Old 9th January 2013, 03:55 PM   #43
WrineX is offline WrineX  Netherlands
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Originally Posted by alexberg View Post
Have you check the bias or have you not??
planning on doing this by laptop, i add a sine wave generator to add a 20K singal while playing music that distort on the esl. but its only to check if this works, i wont like to put up the volume with a 20K tone where the impedance is as low as it gets or i would fie my amp or just goes in protection i gues

i will do this test tomorow when my gf is not home so i can use her laptop
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Old 9th January 2013, 04:33 PM   #44
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by bolserst View Post
Hello Elvee,
Is this the test you propose? (see attachment)

1) With switch open, adjust the output of the preamplifier to a low level that produces audible distortion in the ESL.
2) Close switch to add/mix in a high amplitude ultrasonic signal with the audio going to the power amp.
3) As the amplitude of the ultrasonic signal is increased, the amount of core distortion should decrease resulting in less audio distortion heard in the ESL.
Conceptually, that's it. There are a number of ways of practically implementing it.
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Old 10th January 2013, 12:41 AM   #45
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Originally Posted by bolserst View Post
Hello Elvee,
Is this the test you propose? (see attachment)


@alexberg,
WrineX has tried several power amplifiers with identical results.
It seems unlikely that all of his power amplifiers have DC offset problems.
.
Sure, I said in regard to what I saw on pics posted...

Oh well, even with a crappy 60/50 Hz x-former you won't get "big" distortions @ let's say 500 Hz. The core is not that important at higher frequencies and low amplitudes. What counts is the leakage inductance.

Unless it's a price optimized "special" x-former with low turns count/small core size.

I would of get 100 W 12V halogen lamp dirt cheap transformer, preferably not a toroidal one and check it again. Very often as others mentioned it's a hidden oscillation of an amp due to complex load - it can "rectify" ac signal manifesting as a DC offset.
As to idea of HF tape recorder type bias - I doubt you can get enough HF component to substantially move a working point on the x-former in question. Even with a small size magnetic head and cross section of a magnetic tape one need up to hundred volts of HF bias
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Old 10th January 2013, 03:30 AM   #46
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Originally Posted by alexberg View Post
Very often as others mentioned it's a hidden oscillation of an amp due to complex load - it can "rectify" ac signal manifesting as a DC offset.
I guess a few minutes with an analog scope and/or equipment to run an impedance curve would probably shed some light on the issue.

WrineX, any chance you have a friend who could loan you an oscilloscope or help out with some impedance measurements?
I hope so. Would really be nice to know what this unusual distortion is.

Quote:
Unless it's a price optimized "special" x-former with low turns count/small core size
Very well could be...still waiting to see a pic and some details on size and core type.

Quote:
As to idea of HF tape recorder type bias - I doubt you can get enough HF component to substantially move a working point on the x-former in question. Even with a small size magnetic head and cross section of a magnetic tape one need up to hundred volts of HF bias
I was wondering about that...exercising the core capability at HF would take substantial input voltage as you say.
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Old 10th January 2013, 09:22 AM   #47
WrineX is offline WrineX  Netherlands
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ok so here are 2 pictures of the tranformers. as requested..

the core measures 9.5 cm x 8 and is aprox 2.5 cm thick laminated from 0.5 mm laminates.

they look a bit weird because there cast in some sort of resin wich i cant remove. the baffle of the type of speakers there from was made of this resin so they just did the tranformer in when casting whas not dry yet or even while casting.


and no i dont have anyone with a scope that i know.
Attached Images
File Type: jpg IMG_0638.JPG (284.0 KB, 85 views)
File Type: jpg IMG_0639.JPG (251.1 KB, 86 views)

Last edited by WrineX; 10th January 2013 at 09:25 AM.
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Old 10th January 2013, 10:50 AM   #48
Elvee is offline Elvee  Belgium
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Originally Posted by WrineX View Post
ok so here are 2 pictures of the tranformers. as requested..

the core measures 9.5 cm x 8 and is aprox 2.5 cm thick laminated from 0.5 mm laminates.
That's obviously cheap, power transformer grade metal, no surprise it causes distortion. It can create illusion when driven from a low impedance source, but when the value of the magnetizing inductance influences the output voltage, it shows its true colors
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Old 10th January 2013, 12:46 PM   #49
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<I was wondering about that...exercising the core capability at HF would take substantial input voltage as you say>

Well, for instance, cassette tape recorder 100 mH head 1.2 mA => 37 V@ 50kHz. You can easily visualize the size of the head and the core inside...

On the other hand let's assume x-former's in question core goes into saturation @ 1.5T & 30 Hz and 20V rms thus 30 kHz additional flux density excursion would be 1.5 milliTesla... @ 20V RMS.
Still I would advise to get 12v/230v halogen lamp x-former or two and check - can be used for intended application later. it's like 5-10 eu on sale.
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Old 12th January 2013, 04:23 AM   #50
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Originally Posted by WrineX View Post
ok so here are 2 pictures of the tranformers. as requested.
Thanks
Looks to by E96 size laminations which is the same size used by Audiostatic in their ES-100.

As far as the quality of the iron used, that is hard to say from a picture but it does not look at all like the light grey I am used to seeing on quality audio transformer cores. Also, it looks like there is no insulating wax or varnish between the lamination layers. Is that correct? That would certainly result in increased core losses.
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