... 1. The iron contained in these parts got histeresis when being magnetized by the current flowing 
... 2. The "core" is physically too small and goes into saturation
This is just my idea for an explanation, maybe we have some experts in magnetism here, who can help
by telling us how far for example the end cups (?) of resistors will be magnetized by the current.
Or if a wire contains iron, like the military coax RGxxx...
We all know that if the core of an output transformer of a tube amp is too small there are distortions from saturation.
Also cheap alloys may have magnetic histeresis.
Bernhard
... 2. The "core" is physically too small and goes into saturation
This is just my idea for an explanation, maybe we have some experts in magnetism here, who can help
by telling us how far for example the end cups (?) of resistors will be magnetized by the current.Or if a wire contains iron, like the military coax RGxxx...
We all know that if the core of an output transformer of a tube amp is too small there are distortions from saturation.
Also cheap alloys may have magnetic histeresis.
Bernhard
Magnetic parts sound worse because of...
...the lack of any controlled listening tests to demonstrate this. Note that these parts work just fine in VHF circuits.
Before inventing explanations for a phenomenon, the rational experimenter will first determine if the phenomenon exists.
Oh, yes, and make sure that all your tools are demagnetized. Many of my screwdrivers and wire cutters carry quite a bit of magnetism. It's handy for positioning/removing parts and hardware, but what sort of sonic pollution might it be causing to the gear I build with it?
...the lack of any controlled listening tests to demonstrate this. Note that these parts work just fine in VHF circuits.
Before inventing explanations for a phenomenon, the rational experimenter will first determine if the phenomenon exists.
Oh, yes, and make sure that all your tools are demagnetized. Many of my screwdrivers and wire cutters carry quite a bit of magnetism. It's handy for positioning/removing parts and hardware, but what sort of sonic pollution might it be causing to the gear I build with it?
Magnetic Bias ????
As part of complete and permanent repairs to amplifiers, I often blanket resolder and then clean the amplifier and power supply stages.
On first power up I run the amplifer and allow it to idle for 1 to 2 hours whilst I adjust and allow bias currents to stabilise.
When this is complete, I then apply low level audio for a period, and recheck/adjust bias currents.
During this time, amplifiers subjected to this QA repair method can sound subtly gritty, notchy, strangely distorted and sort of 'wrong'.
Running up to clipping for the first time causes the amp to abruptly change in an instant, sounding 'easier' and more correct, and this new sonic character remains at lower levels and after power down and re-power cycles.
Before running to clip for the first time, briefly running at medium level and back down to original low level reveals subtle changes but not as profound as those after the first clipping event.
I have wondered if the heat of resoldering reduces residual magnetism in component leads, and large amplitude current pulses in the circuit cause a biased remagnetisation of component leads etc.
I have not bothered to find out if soldering provides sufficient temperature to cause minor demagnetisation in typical lead wire materials - feel free to correct me on this.
Eric.
As part of complete and permanent repairs to amplifiers, I often blanket resolder and then clean the amplifier and power supply stages.
On first power up I run the amplifer and allow it to idle for 1 to 2 hours whilst I adjust and allow bias currents to stabilise.
When this is complete, I then apply low level audio for a period, and recheck/adjust bias currents.
During this time, amplifiers subjected to this QA repair method can sound subtly gritty, notchy, strangely distorted and sort of 'wrong'.
Running up to clipping for the first time causes the amp to abruptly change in an instant, sounding 'easier' and more correct, and this new sonic character remains at lower levels and after power down and re-power cycles.
Before running to clip for the first time, briefly running at medium level and back down to original low level reveals subtle changes but not as profound as those after the first clipping event.
I have wondered if the heat of resoldering reduces residual magnetism in component leads, and large amplitude current pulses in the circuit cause a biased remagnetisation of component leads etc.
I have not bothered to find out if soldering provides sufficient temperature to cause minor demagnetisation in typical lead wire materials - feel free to correct me on this.
Eric.
Bernhard said:
Im happy to inform you all that 27MHz is not an issue in audio equipment, even 100KHZ is out of range as far as im concerned. So all of your magnetic parts are fine........pheeew, that was nice to know
You will find magnetic PTFE caps in RF circuits...doing just fine btw.
Magura
Magura said:
Im happy to inform you all that 27MHz is not an issue in audio equipment, even 100KHZ is out of range as far as im concerned. So all of your magnetic parts are fine........pheeew, that was nice to know
You will find magnetic PTFE caps in RF circuits...doing just fine btw.
Magura
You will even find the most ugly ceramic caps in RF circuits.
In RF nobody cares about waveforms, except when the distortion causes undesired higher order power output...
Ever opened a TEK scope ?
You will NOT find a single magnetic resistor in it.
I do a search on google and what I found so far is that
if there is a current there is a magnetic field, and if there is iron, it has to be magnetized, and this means work has to be done, and this means loss.
The work to magnetize the material is not linear, specially arouns zero >> histeresis, so the loss is not linear >> distortion.
if there is a current there is a magnetic field, and if there is iron, it has to be magnetized, and this means work has to be done, and this means loss.
The work to magnetize the material is not linear, specially arouns zero >> histeresis, so the loss is not linear >> distortion.
Magura said:
Im happy to inform you all that 27MHz is not an issue in audio equipment, even 100KHZ is out of range as far as im concerned. So all of your magnetic parts are fine........pheeew, that was nice to know
You will find magnetic PTFE caps in RF circuits...doing just fine btw.
Magura
Well, that and the fact that Bernhard's experiment was not testing the phenomenon that he's concerned about here.
I'll bet the electronics that generated the 27 MHz plasma flame has components with magnetic materials in them. So does a CB radio.
"You will even find the most ugly ceramic caps in RF circuits."
Don't know much about RF, but have seen a comparisson of cap properties on a website, AVX I think, which indicates that ceramic caps have a higher bandwidth than others. This suggests that the word "even", above, is moot. I sounds like cermic would be a neccessity.
Don't know much about RF, but have seen a comparisson of cap properties on a website, AVX I think, which indicates that ceramic caps have a higher bandwidth than others. This suggests that the word "even", above, is moot. I sounds like cermic would be a neccessity.
Bernhard said:
Sure. But how significant it is depends on the material as well as the magnitude and frequency of the magnetic field.
The magnetic domains that grow in response to the magnetic field and are responsible for the residual magnetization can only respond so fast. As frequency increases, they become less and less responsive which means less and less distortion.
Here's a THD versus frequency graph for a Jensen JT-11P-1 input transformer which illustrates this rather well:
An externally hosted image should be here but it was not working when we last tested it.
se
Re: Re: Re: Magnetic Bias ????
As i remember it, the curie temperature is falling with the increasing percentage of copper in the alloy. Am i right on this one?
I know for a fact that some steel alloys (like impax from uddeholm) looses its magnetism to a great extend around 300C
Magura
Steve Eddy said:
As i remember it, the curie temperature is falling with the increasing percentage of copper in the alloy. Am i right on this one?
I know for a fact that some steel alloys (like impax from uddeholm) looses its magnetism to a great extend around 300C
Magura
Re: Re: Re: Re: Magnetic Bias ????
Couldn't tell you for sure.
I'll take your word for it.
I was just pointing out that 100C wouldn't always be a safe assumption.
I think the basic idea though is irrelevant. Even if you wholly demagnetize say the steel end caps of a resistor using thermal energy or a demagnetizer, it's going to go right back to behaving the way it did the moment you apply a signal to it.
There seems to be this notion that this stuff somehow gets magnetized with a certain polarity. But the residual magnetization (remnance) changes polarity with the signal and the polarity it ends up with will depend on the polarity of the signal when it stopped.
But of course as soon as you turn the signal on again, the polarity of the residual magnetization changes again.
se
Magura said:
Couldn't tell you for sure.
I'll take your word for it.
I was just pointing out that 100C wouldn't always be a safe assumption.
I think the basic idea though is irrelevant. Even if you wholly demagnetize say the steel end caps of a resistor using thermal energy or a demagnetizer, it's going to go right back to behaving the way it did the moment you apply a signal to it.
There seems to be this notion that this stuff somehow gets magnetized with a certain polarity. But the residual magnetization (remnance) changes polarity with the signal and the polarity it ends up with will depend on the polarity of the signal when it stopped.
But of course as soon as you turn the signal on again, the polarity of the residual magnetization changes again.
se
I fully agree steve. I joined this thread cause i think its sad to see so big amounts of money/- time wasted on something that is very questionable.
Its like with the isolation and the internal wireing....all theese 3 factors( i believe in only one of them(the one thats proven, but proven minimal influence)guess wich) are not even going to give you something you could call a percentage of improvement. Opposed to looking at the active devices. Even some of the passives(like caps and resistors) have some audiable effect for an amp.
If only people read some of the articles posted on passdiy.com
......it would be a little easier.
As posted earlier, magnetic components are used in RF circuits at many times the frequencies we see in an amp, now what makes people believe they wouldnt have solved the problem (or at least adressed it) if it was for real? After all, the RF guys have a somewhat bigger budget than the audio guys.
Magura
Its like with the isolation and the internal wireing....all theese 3 factors( i believe in only one of them(the one thats proven, but proven minimal influence)guess wich) are not even going to give you something you could call a percentage of improvement. Opposed to looking at the active devices. Even some of the passives(like caps and resistors) have some audiable effect for an amp.
If only people read some of the articles posted on passdiy.com
......it would be a little easier.
As posted earlier, magnetic components are used in RF circuits at many times the frequencies we see in an amp, now what makes people believe they wouldnt have solved the problem (or at least adressed it) if it was for real? After all, the RF guys have a somewhat bigger budget than the audio guys.
Magura
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