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Use of Ferrite Core Chokes . . .


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I have a good friend that uses Ferrite Chokes on many of his analog audio interconnects.

 

My friend has been an audiophile for years. He is high end. His system is one of those outstanding/unbelievable systems. He has two volume controls to turn up because he has two Krell preamps that are used independent for left/right channel. He has two Krell KPA Phono Pre-Amps that he uses in an independent left/right configuration. Meadowlark Nightingale Speakers. It is all nice nice equipment. I trust him for analog audio advice.

 

So he loaned me some nice interconnects and I noticed the chokes on the output end of cables. He said he has chokes on several of his interconnects. My question for him was how it adversely affects sound and he said "none".

 

Do you use chokes on your analog audio cables?

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Ferrite beads? No, generally they are used for higher frequencies as I understand it. I have them on a couple of USB cables and the AC cables for some digital gear.

Forrest:

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Do you use chokes on your analog audio cables?

 

This type of choke is also called "common mode choke", because it is used to filter common mode noise travelling over cables. Think of it as one turn of a wire around a transformer core. The magnetic flux induced by differential signals (on symmetric transmission lines) compensates each other, so that the signal is not influenced. On common mode signals (travelling over both wires in the same direction) it operates as a choke, because the resulting induced magnetic flux is non-zero.

 

The effect on signals below 100..200 MHz is negligible. Below is a figure from a manufacturer's application manual showing the effect of a common mode choke on a USB cable.

 

common-mode-choke.jpg

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Ferrite beads? No, generally they are used for higher frequencies as I understand it. I have them on a couple of USB cables and the AC cables for some digital gear.

 

Hi 4est - I've heard mixed things about Ferrite beads on USB cables. Mainly that the beads change the signal for the worse in a measurable way. That's just what I've heard and have no experience listening with/without beads or have I seen the measurements.

 

What's your impression of with and without the beads?

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Hi 4est - I've heard mixed things about Ferrite beads on USB cables. Mainly that the beads change the signal for the worse in a measurable way. That's just what I've heard and have no experience listening with/without beads or have I seen the measurements.

 

What's your impression of with and without the beads?

 

Chris:

 

Honestly I do not know as I have not compared the same cable with and without. I am not sold on the concept, but they were an early "audiophile" purchase. One of these I will look into it and get back to you.

Forrest:

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DSD>Pavel's DSC2.6>Bent Audio TAP>

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I have added ferrites to all my USB audio cables. Placed 0.5 cm from the DAC-end connector. Cleans up the high frequency interference from the cable and reduces amount entering DAC's sensitive clocking circuits. Any cable is more or less an antenna and ferrites reduce this behavior. I have also ferrite on my S/PDIF cable from hiFace to my DAC to reduces RF pickup there too. The result is so low jitter that it falls below my measurement resolution, even with cellular phone or WLAN AP is nearby.

 

Those are also commonly seen inside equipment on the incoming power wires, unless the device has power line filter (like Mytek and my DAC where there are more efficient coiled ferrite chokes inside).

 

Most of the USB cables that come with my cellular phones, digital cameras or such are equipped with ferrites to keep nasties like GSM's rattling out. Also all my DVI and analog VGA cables that came with monitors are equipped with ferrites at both ends.

Degradation of the USB signal itself is not an issue as long as the 0/1 states can be correctly detected at end, since with async USB there's no relevant clock information on the cable. E-MU 0404 USB cable also comes with ferrite.

 

One easy test is to have a phone call open in GSM phone and then take the phone next to audio/USB cables and observe for any difference in sound. In case there's audible buzz or rattling then the device's EMI/RFI tolerance is really poor.

 

Most of the time ferrites are not needed on analog cables, unless the device is really wide band, because even first-order passive low pass filter at the device's input would already cut anything that the ferrite would block. However it may be useful for reducing nasties traveling on grounds.

 

But I know lot of people have strong opinions on the matter, so I don't care to argue too much about the topic. I just do what I find best through objective measurement and analysis, for my systems.

 

(and yeah, there are about 10 WLAN networks nearby, we have six devices in the family talking to cellular network and I can see FM/TV broadcasting antenna mast from my window, so there's some amount RF in the air here)

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I don't use chokes. I don't think I've heard or seen them on analog cables in recent memory.

 

Not in recent memory. They were a fashion for a while 20-odd years ago. I had them on some analog cables for a while (cheap enough just to try out), noticed nothing immediately apparent either way, so I got rid of them. The cables I own now wouldn't support them physically.

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I would not ever use a ferrite bead on an analog signal cable. These beads are magnetic, and my experience is that magnetic materials and analog signals do not get along well.

Charlie Hansen, (lead man at Ayre) has described negative effects on sound quality of using ferrites on AC power cables, and for incoming AC wires in components. What he reported is that under first use conditions, the ferrites can produce better sound when used on AC supply wiring, but that over time, the ferrites would become magnetized, and then would produce a hardening of the sound. He tested and confimred his observations by using a tape de-magnetizer on the ferrites under test: when de-magnetized the hardening of the sound dissappeared. He went forward, and developed a different type of filter (using non-magnetic materials) for use inside Ayre components on the incoming AC.

As is noted here, ferrites are standard issue on many USB, And other, computer peripheral cabling. Considering that adding these ferrites costs money, I suspect this is likely done to keep RF emmissions down, for passing FCC regs.

I know of some Class D amplifier manufacturers which place ferrites on the internal speaker output wiring... I like to remove these, and apply other RF reducing materials which are non-magnetic instead.

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Don't know if my experience applies to the audio side of things, but ferrite chokes on HDMI cables for HD video have made a HUGE difference in lowering digitized noise entering the picture. In my case, this was a clear, incontroversial case where random noise was visible but once the choke was placed on the cable, the noise disappeared completely......oh, also helped with slight ghosting on composite analog cables over a long 50ft run to a DLP projector.....which was only visible on the B channel of the RGB.

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  • 4 months later...

Versalab Wood Blocks. Not sure if these use ferrite beads?

 

But, have found that if I use one on my Mini server, I get a clearer and more relaxed musical presentation than when I don't use one. No negatives...all better.

 

Had one lying around from when I had a Theta Gen Va and Basic transport. That combo was musical and dynamic, but a bit rough around the edges and the blocks tamed the beast a bit.

 

Could be that the RFI filter has a "two way" impact, knocking down noise from Mini to audio system?

 

Anyone else monkey around with one of these?

Tone with Soul

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I bought a 6-pack of them and was able to barely fit them on a Kimber PK10 PowerKord, and am pretty confident that the SQ deteriorated so I removed them.

 

Also, I have both the silver/copper (FS here on CA), and an all silver Kimber USB cables. The silver/copper cable comes with them at both ends, while they do not come with the silver, but can be requested from Kimber, if needed. Nate Mansfield from Kimber suggested that they just be removed from the silver/copper cable unless there was an issue with RF interference. So, that is probably my advise... just add them if you have an issue with interference or noise.

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  • 4 months later...
"Ferrite Core Chokes" are very good at solving some interference problems, but they have to be used correctly.

 

Jim Brown has several papers on using them correctly.

 

Audio Systems Group, Inc. Publications

 

Nice link particularly for ham radio operators...lots to read.

 

From what I read, YMMV re using ferrites on analog audio cables but wondered what people think about adding split-core (clamshell type) ferrites to the power cords of

 

1) PC/monitor/printer systems serving as music server that are connected via USB to an audio system DAC?

 

2) UPS supplying power to the PC-based music server even tho' UPS is on separate circuit at the master panel?

 

Even tho' this AC is supplied from separate circuit at master panel, plugging a PS Audio "Noise Harvester" indicates that there is significant line noise and, depending on how may dimmable lights (halogens, LEDs, etc) are active, enough to keep the Harvester almost constantly lit. This suggest that this digitally generated noise travels from the device back thru the AC circuits where it can interfere with device(s) on a separate circuit, e.g., the DAC.

 

Unfortunately given space contraints, my PC music server and DAC are separated by about 12 feet necessitating a long USB. Am looking at alternative connectivity but have noticed that USB cables with more (better?) shielding seem to result in less noise on the audio system even when system is on but not playing.

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Glad you brought this thread back up. I pulled the 6 pack of clamshell ferrite cores back out when I started rewiring all of the digital / network related items on another outlet. I'll snap some pics and feedback when I'm finished with the project tomorrow after a few more things come in from MonoPrice.

A Digital Audio Converter connected to my Home Computer taking me into the Future

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The iFi Gemini usb cable I recently purchased has three metal oxide ceramic RF silencers, one of which is adjustable. Is this a related concept to the Ferrite core chokes (a different mechanical method of addressing RF)?

 

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Yeah, same thing Blake. Basically high-frequency RF is converted to heat in the ferrite core.

 

I started to think about it again when I noticed some AudioQuest NRG 1.5's have them on their C7 cable and thought it wouldn't be a bad idea to throw one on the MacMini - both to reduce incoming RF as well as emitted RF...I'm seeing how much I can improve the MacMini as a source. Have an Oyaide C7 coming in for it now... Then, I went a bit further and even added one to the Airport Extreme, etc.

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Ferrites are metal oxides, and so most likely yes. They are not mechanical however, but electrical in nature by effecting the self inductance of the wire it surrounds. Hence it is called a choke which is an inline inductor (which reduces high frequencies).

 

The iFi Gemini usb cable I recently purchased has three metal oxide ceramic RF silencers, one of which is adjustable. Is this a related concept to the Ferrite core chokes (a different mechanical method of addressing RF)?

 

iFi-audio Gemini

Forrest:

Win10 i9 9900KS/GTX1060 HQPlayer4>Win10 NAA

DSD>Pavel's DSC2.6>Bent Audio TAP>

Parasound JC1>"Naked" Quad ESL63/Tannoy PS350B subs<100Hz

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and my aes/ebu cable:

 

Picture007_zps01cbc12b.jpg

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A quick note on the PS Audio Noise Harvester: these devices are specifically designed to target low frequency noise, I cannot now remember the frequency range, but we are talking kHz noise, and not MHz noise. You can have tons of MHz noise and the NH will not light. So the noise which the NH responds to is not anywhere near the same frequency range where ferrites would be effective. Indeed the Noise Harvester was specifically designed to complement the vast majority of passive line conditioners, which almost universally target high frequency noise (which is easier to filter generally).

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Nice link particularly for ham radio operators...lots to read.

 

From what I read, YMMV re using ferrites on analog audio cables but wondered what people think about adding split-core (clamshell type) ferrites to the power cords of

 

Jim Brown did it on the main power line to his house. (complete with photo on page 23).

 

'A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing'

Revision 5a 5 Jun 2010

by Jim Brown K9YC

Audio Systems Group, Inc.

Audio Systems Group, Inc. Home Page

 

http://www.audiosystemsgroup.com/RFI-Ham.pdf

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Jim Brown did it on the main power line to his house. (complete with photo on page 23).

 

'A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing'

Revision 5a 5 Jun 2010

by Jim Brown K9YC

Audio Systems Group, Inc.

Audio Systems Group, Inc. Home Page

 

http://www.audiosystemsgroup.com/RFI-Ham.pdf

 

Re the page 23 "book" reference, the 240V drop to my home is about an 1 (one) inch in diameter. Not sure whether anyone sells split clamp-on ferrites this large. Jim does not say what type of ferrite core was used...#31, #43 (which I am told is sort of all-purpose when noise frequency is not known), etc. While many of the recommendations on noise abatement are probably transferrable to the audio hobby, Jim does come from a radio background where antennas and other long cable runs (which can act as antennas) are being treated.

 

To this point, I have personally noted that more shielded USB cabling seems to be quieter than garden variety cable but I am also using long runs which may exacerbate any potential noise issue. I will be looking at fiber/USB connection between my PC and DAC to galvanically isolate the audio system from the PC.

 

Have a bunch of split ferrites which I am pretty sure are not identified as to what type they are but it may be worth putting them on the power cords of my computer gear to see if I notice any difference.

 

I understand that the Noise Harvester may not treat Mhz noise frequencies. Paul at PS Audio commented that I probably cannot hook up enough NHs (@ $50-100 a pop) to kill the noise they are indicating, regardless of its frequency. Dimmable light bulbs DO seem to exacerbate the noise being picked up by the NHs.

 

Despite my success to date getting a computer-based music server operational, it is becoming obvious that PnP systems are not quite that simple... Sigh!

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BigGuy: Yes, typical light dimmers are one of the worst culprits when it comes to AC line noise. They should not be in use in your home during critical listening sessions-if they are all the way off they are fine, and all the on usually OK as well, but if any dimming is used they emit huge amounts of noise. These things are way worse than SMPS, in fact, I am little surprised that they are approved...

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