Ferrite bead

[Smislov]

Hi everyone,

Got these cables as a gift. They come with ferrite bead. What's its use? Does it improve quality of sound? Is it there to only lower the electronic noise? Can anyone explain? Thanks

 

[somebodyelse]

They're usually used to reduce RF interference, but if the manufacturer was seriously trying to do that they'd have put them closer to the connectors. They're probably being used here for decoration, like the sleeving. It looks like they're the clip-on variety so you can try removing them and see if it makes a difference. I wouldn't expect one, but it's possible depending on how sensitive your equipment is to RF, and how much there is in your area.

 

[Lambda]

Common misconception that they only work on RF.

RCA cable Magnetic interference measurement and comparison

Cables are cables and there is no difference?! I designed a test to see if they perform significantly different in therms of "magnetic shielding" or Leakage inductance. This test dose not test for ground loop currents but interference from close by magnetic in homogeneous magnetic files. The...

www.audiosciencereview.com

For low voltage ground loop nose they do a good job and reduce common mode currents significant from 1kHz and up.
They do nothing to the signal itself (in a good coax cable) but they help with noise Rejection. not only RF nut also audio frequency.

 

[audio2design]

Realistically given the typical impedances of the source /load and intentional / parasitic capacitances and other parasitics even common mode they are useless or close to it below a MHz if not a few MHz.

 

[Lambda]

Realistically given the typical impedances of the source /load and intentional / parasitic capacitances and other parasitics even common mode they are useless or close to it below a MHz if not a few MHz.

Whats the Typical impedance between tow Class 1 devices? how dose the impedance between them change if you connect them with short RCA cables?

even common mode they are useless

Only usefull for common mode that’s the point.

"MHz if not a few MHz."
My testing showed Different results.

You already said Twisted pair is more Immune to Magnetic interference compared to Coax.
This is also False an i have tested it.

 

[antcollinet]

Characteristics of such ferrites is basically transparent at audio frequencies. They are for RF only - and are typically used to limit RF Output from the kit connected to (ie to reduce radiated emissions from the kit for standards compliance). I have seen them use also to limit incoming interference, but this is generally a sticking plaster for a broken design. If they are being sold as any sort of audio improvement then it is just more snake oil.

 

[maty]

Cheap ferrites > 1 Mhz, video.

They are of little use in these cables, except to increase the price.

Würth ferrites (me) > 150 kHz. Other brands > 300 kHz.

 

[Lambda]

Characteristics of such ferrites is basically transparent at audio frequencies. They are for RF only

This is a false statement. The material works just as well if not better at low frequency's
They have now effect on the audio Inside the cable because they work as a common mode choke only on commone mode currents.
There is no Mateial Based Lower Frequency limit.

And if so there is a bazillion different Ferrite materials with different property's out there what material are you actually talking about.

If they are being sold as any sort of audio improvement then it is just more snake oil.

They are soled from electronic distributors as common mode choke and they work as common mode choke also at 1khz as i have shown.

Cheap ferrites > 1 Mhz

Again there is no Mateial Based Lower Frequency limit

Würth ferrites (me) > 150 kHz. Other brands > 300 kHz.

why would it be?


Do you Guys know the typical µr of the materials your talking about or the AL value of a core?

 

[DSJR]

Back in the mid 90's, I lived in a UK town which seemed hobbled with diabolical mains quality, this I believe before smps supplies and audio gear in general 'supposedly' became more immune to mains interference. I was encouraged to use clip on ferrites starting with the mains leads and of course back then I was keen to 'experiment' subjectively... Such ferrite clips are CHEAP TO BUY and easily removed, so what the heck!

All I can say is, that back then, fitting one each to my active speaker mains cables, I 'imagined' a slight improvement in the bass and when I removed them, I also 'imagined' it wasn't quite as good, so I left them there. i dadded ferrites to the 3m long cable from socket to distribution block that fed the preamp and sources and also tried them on the sources alone. The (AVI) preamp was absolutely immune (as you'd expect from a designer who cut his teeth with rf and early digital engineering) but the CD players I used did seem to benefit. One interconnect we sold using microwave cables based on a silver plated core in a flexible copper 'pipe' also seemed directional and sensitive to such ferrites (absolutely NO objective backup to this though). Adding more than one to a given mains cable made no further perceptible difference at all, but these things were cheap so I left them there, one per mains cable.

Here on the coast, the mains is good and the local heavy industry has their own separate mains supplies to the town. I still retain the clip-on ferrites on mains and some analogue interconnects (too damned lazy to take them off frankly and as many of the laptop sipplies have these ready moulded into their connecting cables, I see no harm) and also the 'Roxburgh 6A filters' on my older digital sources which used to make a difference.

So to the OP, two per cable is largely unnecessary really but you could easily remove all four and see if it makes any difference. If it genuinely doesn't you're laughing I'd politely suggest your mains cables would be the place to try them?

 

[Lambda]

Lets look at Feroxcube 3e12
some http://ferroxcube.home.pl/prod/assets/3e12.pdf

µi is defined at <10khz... (strange since i heard only Würth ferrites work below 150 kHz. )
They even come with a graph showing permeability vs frequency... no surprises it is Flat for low frequency.

 

[antcollinet]

This is a false statement. The material works just as well if not better at low frequency's
They have now effect on the audio Inside the cable because they work as a common mode choke only on commone mode currents.
There is no Mateial Based Lower Frequency limit.

They can ONLY be common mode because they go around all conductors. Any differential inductance is cancelled out.

And the permeability unimportant when looking for impedance of a ferrite bead since there is effectivley only one turn in the inductor (the wire going through it) - most of the impedance comes from from magnetic losses at higher frequencies. See "RELATIONSHIP BETWEEN COMPLEX PERMEABILITY AND IMPEDANCE" here: https://incompliancemag.com/article/using-ferrites-to-suppress-emi/

(edited for clarity)

Feel free to find a datasheet for any ferrite bead that has any impedance at all at audio frequencies. Most have nothing below 1MHz.

The data sheet for ferroxcube beads doesn't even specify an impdedance below 1MHz. But here is a typical graph of impedance by frequency:

 

[MediumRare]

Look at Amir’s study of RCA cables. There must be a problem to solve before there can be any benefit from a solution. Show us the problem, please. Otherwise: snake oil.

 

[Lambda]

They can ONLY be common mode because they go around all conductors. Any differential inductance is cancelled out.

This is the whole point and thats also what im saying...

Only usefull for common mode that’s the point.

Feel free to find a datasheet for any ferrite bead that has any impedance at all at audio frequencies. Most have nothing below 1MHz.

Z = jLw
At low frequency we don't care at all about the complex impedance μ’ at low frequency is is way bigger compared to μ’’
So we assume Loss at about <10khz is Negligible so we just care about "real" inductance.
Inductance is nearly constant from 1kHz to 20kHz.

Look at Amir’s study of RCA cables. There must be a problem to solve before there can be any benefit from a solution.

(although my AP analyzer may be more immune to this noise than your audio gear). So assuming you avoid touching a transformer to your cables, electrically all three cables have bandwidth that exceeds 200 kHz, and any noise or distortion is the result of the

Note that this is an ad-hoc test. Where you position the transformer on the cable may matter. As could the length of the cable, etc. But as a quick test, it does show us something.

So you Never heard from some one having "Noise" issue when connecting a PC,TV, AVR and usb DAC, Active monitors/Sub with over RCA?!
Just search for "Noise and PC or USB DAC" in this forum.
it is a very real phenomena.

I'm not calming the cable/ferrite improve the music or the bass or something magical...
It’s just helping a bit with Noise rejection.

This problem was not recreated in amirs Test Although it happens in real live alle the time...
Exactly as you say "There must be a problem to solve before there can be any benefit"

If your not able to recreate the problem how can you make a competent an conclusive test if something helps with this problem?
You can’t.

I was able to recreated the problem. isolated the influence from different sources for the problem
common mode current, common mode voltage and close Magnetic fields.
( i'm missing a test on electric fields / captive coupling )

And i was able to show that for every case there is >10dB difference within the audible band between a bad and a good cable.

 

[antcollinet]

Which just goes to show a little knowledge is dangerous. The only way these devices can reduce interference is with impedance. Look at the impedance curve even for the ferrox cube you referenced. Nothing below about 100kHz - very little below one MHz.

 

[Lambda]

The only way these devices can reduce interference is with impedance

Z = jLw

Inductance causes impedance at ac you can calculate it your self since L is constant at low Frequency you don’t need a curve for this.

 

[fineMen]

Inductance causes impedance at ac you can calculate it your self since L is constant at low Frequency you don’t need a curve for this.

Makes sense with a coaxial?

Once I needed a new stylus. Went to the store, and had to wait a bit. Some customer was talking to the shop owner about the merits of his very new purchase, namely two coax signal cables. Yep, after he payed, and it was handed out to him already, without the box. Seems he 'tested' them before. While throwing the common 'audiophile' blurp to the shop owner he got that much excited, that he bent the cables back and forth automatically.

Shop owner had enough and told him in reply, that he would break the cables soon, if he wouldn't stop. So much on proper 'break in'.

 

[antcollinet]

Inductance causes impedance at ac you can calculate it your self since L is constant at low Frequency you don’t need a curve for this.

Right (if you know the inductance which tends not to be specified) - which is presumably where the manufacturers impedance curves come from. You're aware that an inductor acts as a low pass filter? So low frequencies (including noise/interference) are passed without attenuation. (Because impedance at low frequency tends towards zero)

Again - find me a data sheet for a cable core with a specified (and useful) impedance below 20KHz, and I'll spin on a sixpence and admit you've been right all along. I'll leave it there until you've found one.

 

[Zensō]

This is from an article by John Seaber at JDS Labs discussing testing methods they used for the ODAC. He’s mentioned in a number of places over the years that they’ve found ferrite beads to have measurable effects on USB.

“ObjectiveDAC was designed for measurable and audible perfection. Reduced performance from ODAC RevB would be absolutely unacceptable, so we took great care in checking our work.

Engineering test methods impact test results. While THD+N, frequency response, and crosstalk are straightforward, even these basic tests are impacted by audio analyzer setup parameters and real world hardware setup. Certain ferrites on the mini-USB cable improve dynamic range by up to 10dB versus an ordinary USB cable. More complex tests like Jitter and IMD produce surprisingly different results based on signal strength, averaging, etc.. As Yoyodyne and I analyzed performance of the original ODAC through a TDK ZCAT2035-0930 ferrite equipped USB cable via dScope audio analyzers, it was clear that NwAvGuy had utilized averaging and custom dScope routines. We would never be able to definitively duplicate his work due to unknown averaging, scripting variables, and exact ferrite type.”

 

[Lambda]

Right (if you know the inductance which tends not to be specified)

Z = jLw
You can look up Z for a specific frequency in the datasheet. for low frequency Z is about constant.
But if you don’t trust this theory measure it yourself. i did so btw. because most of the ferrites i have come without datasheet.

aware that an inductor acts as a low pass filter? So low frequencies (including noise/interference) are passed without attenuation.

And whats the cut of frequency of this filter?
The formula is w=R/L

Whats the filter order?
Sure low frequencies pass better but not "without attenuation" but with less attenuation.

Again - find me a data sheet for a cable core with a specified (and useful) impedance below 20KHz, and I'll spin on a sixpence and admit you've been right all along. I'll leave it there until you've found one.

You make the mistake to care about the Restive region.
Ferrite material made for EMC/EMI is intentionally lossy at higher frequency therefore it dissipates extra "RF" energy into heat.
this gives it an apparent higher Z at this frequency of 100s of Ohms.
At lower frequency its all most purely inductive.
therefore Z = jLw
L is of cause dependent on core shape and windings
From core shape and size you get Core AL with the core AL you can the inductance.

 

[audio2design]

Lets look at Feroxcube 3e12
some http://ferroxcube.home.pl/prod/assets/3e12.pdf

View attachment 165073

µi is defined at <10khz... (strange since i heard only Würth ferrites work below 150 kHz. )
They even come with a graph showing permeability vs frequency... no surprises it is Flat for low frequency.

3e12 is used for low frequency common modes and differential mode inductors. It's not what cable clamp ferrites are made of. Not that you couldn't but not the usage since low frequency common mode is rarely an issue and if you attack common mode in the signal range invariably you have differential leakage inductance that hurts the signal but it is beneficial for power EMI usage.

Clamp EMI filters are typically targeted in a range of about 2-30Mhz, 20-200mhz, and 100-1000Mhz approx. The high frequency ones have virtually no impedance at audio frequencies and even the low frequency ones have almost nothing. The graph you posted shows that very clearly even though that is for a high frequency ferrite but also it appears to be for a bead ferrite not a clamp. It shows a couple ohms at 1Mhz ... That's not going to have any effect in audio interconnects at 1mhz let alone 20khz.