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Old 5th January 2013, 02:33 AM   #31
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Quote:
Originally Posted by WrineX View Post
made mistake there left is V2 right V1 ofcourse





Here is a picture wat happens i think.

is a screenshot taken in protools of a sweep i played with and without cap. upper is with lower is without , (V1 bot V2 top)

as seen it has problems to get positive. it folows the control nicely in the negative but crap in the positive.

also is out of phase as you can see,but thats explained by the phase measurement, the picture is from a frequency somehwere in the crossover range, where the signal is out of phase as you can seee in the holmimpulse measurement. so thats ok , only thin not ok is the fact that positive and negative ar not equal.
What I can see it's a definite DC offset most likely at the amp's output (??). Do you have mutimeter/voltmeter of any kind?

Last edited by alexberg; 5th January 2013 at 02:39 AM.
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Old 5th January 2013, 03:31 AM   #32
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Quote:
Originally Posted by WrineX View Post
if i remove the panels from the trannie, when playing the distortion stays the same on the headphone.
When you removed the panels and still heard the distortion at V2 but not V1, was the HV bias supply still connected to the transformer? or did you disconnect it from the transformer when you removed the panel connections.


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Originally Posted by alexberg View Post
What I can see it's a definite DC offset most likely at the amp's output (??)
V2 is sampled after the signal has passed thru the 15uF capacitor so even if the amp did have some DC offset, the capacitor should effectively remove it I would think.

I'm still trying to come up with a reason for this type of distortion at V2 but not at V1...something very odd is going on.
I keep thinking there is something we are missing.

Last edited by bolserst; 5th January 2013 at 03:34 AM.
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Old 5th January 2013, 10:30 AM   #33
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by alexberg View Post
What I can see it's a definite DC offset most likely at the amp's output (??). Do you have mutimeter/voltmeter of any kind?
i have a simple multimeter. but that means 3 of my amps have this ?

, and what can i do to check ?




Quote:
Originally Posted by bolserst View Post
When you removed the panels and still heard the distortion at V2 but not V1, was the HV bias supply still connected to the transformer? or did you disconnect it from the transformer when you removed the panel connections.
i kind have to admit i think i did not disconected the 0 from the tranie to bias, because i thought without the 2 stators its not a capacitor anymore. i did disconnect the bias from the wall socket to see if anything changed on the headphones. but ofc nothing happend.

Last edited by WrineX; 5th January 2013 at 10:34 AM.
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Old 5th January 2013, 11:44 AM   #34
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Quote:
Originally Posted by WrineX View Post
sorry i really have no idea. im not really into transformers , i just got al of these out of solostatic ESL's where the panels needed new coating. i will make a photo.later on.
You need to know what alloy it is made of. A photo won't help.

For this kind of application, where the magnetizing inductance of the transformer plays a big role, a very low coercivity material is essential, otherwise it will cause the kind of problem you notice.

As a temporary fix and to confirm the effect, you could mix your low level audio with a high level ultrasonic frequency (>20KHz more or less, depending on your hearing abilities).
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Old 5th January 2013, 02:34 PM   #35
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You may check DC level at the amp output/speaker input at small and probably medium power level. I am not sure, though, that your Mmeter can handle presence of large AC component at small DC range.
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Old 7th January 2013, 07:46 AM   #36
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Will give is ą try
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Old 9th January 2013, 03:54 AM   #37
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Originally Posted by Elvee View Post
...For this kind of application, where the magnetizing inductance of the transformer plays a big role, a very low coercivity material is essential, otherwise it will cause the kind of problem you notice...
It seems that most core related distortion mechanisms, including that due to DC offset or residual magnetism that I had suggested, result in distortion that gets worse with increasing volume which does not match the symptom described by WrineX.

Rereading the post by Elvee the comment about inductance playing a big role suggested to me a possible mechanism for the distortion. The inductance of the primary and the series capacitor form a voltage divider. The larger the primary inductance, the larger the portion of the input voltage that will be present across the primary.

Now, the primary inductance of all iron core transformers is a function of the number of turns and the permeability of the core. The permeability of the core is a function of the input voltage, increasing from some initial value of usually several 1000 and peaking just before core saturation starts. This results in the primary inductance portion of the voltage divider being a function of the input voltage. Usually the primary inductance is large enough that it's impedance is significantly larger than that of the series capacitor.

But poor transformer iron has very low initial permeability and would result in very low primary inductance for low input voltages. So, only a small portion of the input voltage appears across the primary. This also means that the majority of the voltage drop due to any current distortion caused by the core will show up across the capacitor and distort the voltage fed to the primary. As voltage amplitude increases, the primary inductance increases and a greater portion of the input voltage will appear across the primary and distortion is reduced.

The fix is to use better core material, or drive the transformer from a lower impedance source (ie no series impedance like capacitor)
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Old 9th January 2013, 07:48 AM   #38
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Quote:
Originally Posted by bolserst View Post
Rereading the post by Elvee the comment about inductance playing a big role suggested to me a possible mechanism for the distortion. The inductance of the primary and the series capacitor form a voltage divider. The larger the primary inductance, the larger the portion of the input voltage that will be present across the primary.

Now, the primary inductance of all iron core transformers is a function of the number of turns and the permeability of the core. The permeability of the core is a function of the input voltage, increasing from some initial value of usually several 1000 and peaking just before core saturation starts. This results in the primary inductance portion of the voltage divider being a function of the input voltage. Usually the primary inductance is large enough that it's impedance is significantly larger than that of the series capacitor.

But poor transformer iron has very low initial permeability and would result in very low primary inductance for low input voltages. So, only a small portion of the input voltage appears across the primary. This also means that the majority of the voltage drop due to any current distortion caused by the core will show up across the capacitor and distort the voltage fed to the primary. As voltage amplitude increases, the primary inductance increases and a greater portion of the input voltage will appear across the primary and distortion is reduced.

The fix is to use better core material, or drive the transformer from a lower impedance source (ie no series impedance like capacitor)
Yes, in short it is caused by the non-zero coercivity resulting in hysteresis and causing distortion, just like in raw magnetic recording.
The fix, temporary or definitive, could be the same: add a high frequency bias.
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Old 9th January 2013, 09:48 AM   #39
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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
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Old 9th January 2013, 10:54 AM   #40
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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
Before jumping to conclusions, you should confirm the core material is actually the cause of your problems, otherwise you could spend money for nothing
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