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Old 1st February 2004, 07:37 AM   #1
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Default Magnetic parts sound worse because of...

... 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
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Old 1st February 2004, 01:33 PM   #2
SY is offline SY  United States
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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?
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Old 1st February 2004, 01:40 PM   #3
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Quote:
Originally posted by SY
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.

Bringing a magnetic resistor near to the coil of my 27 MHz plasma flame causes it to go off.

If it is found that hysteresis or saturation cause errors = distortion, no golden ears will be needed anymore for proof.
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Old 1st February 2004, 02:02 PM   #4
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Default 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.
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Old 1st February 2004, 02:05 PM   #5
Magura is offline Magura  Denmark
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Quote:
Originally posted by Bernhard



27 MHz .


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.

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Old 1st February 2004, 02:09 PM   #6
Magura is offline Magura  Denmark
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Default Re: Magnetic Bias ????

Quote:
Originally posted by mrfeedback

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.

Off the top of my head, you dont need to get much on the other side of 100C to influence magnetism.

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Old 1st February 2004, 02:23 PM   #7
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Quote:
Originally posted by Magura



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.
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Old 1st February 2004, 03:02 PM   #8
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Default Re: Re: Magnetic Bias ????

Quote:
Originally posted by Magura
Off the top of my head, you dont need to get much on the other side of 100C to influence magnetism.

Magura
Thanks.
If this is the case then this may be an explanation for the sonic changes.

Eric.
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Old 1st February 2004, 03:13 PM   #9
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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.
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Old 1st February 2004, 03:21 PM   #10
andy_c is offline andy_c  United States
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Quote:
Originally posted by Bernhard

In RF nobody cares about waveforms, except when the distortion causes undesired higher order power output...
Not true. In Doppler radar receivers for example, the level of third-order intermods determines how far below clutter that a target can be resolved. Most RF amplifiers have an OIP3 specification, because it's important in many applications.
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