AudioCircle
Audio/Video Gear and Systems => Power Conditioning => Topic started by: Escott1377 on 11 May 2015, 02:34 pm
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I have read both answers - yes and no.
Belden makes a 12 AWG cable that is shielded, but I could not find a 10 AWG cable that is shielded.
I have ready to use a ferrite choke to help with reduce effects of EMI.
I am going to take a shot at making a few power cables.
Any help is appreciated.
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Shielding adds capacitance. All my power cables are unshielded.
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Simple answer is "no". Power cables do not "require" shielding. But whether or not shielding is a good idea for power cables will be system dependent. Unfortunately, you will need to try both approaches to determine what will be best in your system.
A power cable can act as an antenna, and as an antenna it could both broadcast, and receive, airborne noise. This may, or may not, be a problem in your system context.
Personally I prefer unshielded power cabling, but I do like to add RF damping (which some might consider shielding, but really is not) to some cables, especially those for digital components or other components which may generate high frequency noise (RF potential).
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I plan just using the unshielded at 10 AWG.
If it's a problem, I can redirect.
I am having a discussion w/ someone that want to use carbon fiber on his cable build.
I think this will be shielding the cable and thus increase capacitance.
His thoughts are sine the shield will not be tied to the ground that this will not be true.
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'barrows' answer is most excellent!
The added capacitance is trivial.
Because the two conductors are very close together, current noise is canceled at about a 2 inch distance.
This leaves the airborne noise antenna problem. Twisting the conductors helps and shielding helps.
'ground' has little to do with the solution, but most any shield should be connected to the chassis.
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If your power cables are making audible RF in the hearing spectrum, you probably have bigger issues barring a radio tower for a neighbor.
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Paranoia takes over and running power cables with some distance of signal leads is very difficult and in the back of my rats nest, power cables touch signal cables in a few places.
All my power cables are screened, with both ends terminated at the earthing pin. System is 230V.
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It's not about audible RF, it's about how the RFI interference affects (effects?) a circuit once it sneaks into a component. A cell-phones 2GHz signal can be bad news for some hi-fi equipment.
Jim Brown being both the AES committee co-chair on EMI/RFI and a Ham radio operator writes on the problems:
"RFI, Ferrites, and Common Mode Chokes For Hams"
http://www.audiosystemsgroup.com/RFI-Ham.pdf
"RF Interference in Audio Systems"
http://www.audiosystemsgroup.com/AES-RFI-SF08.pdf
about 50 more Jim Brown papers:
http://www.audiosystemsgroup.com/publish.htm
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It's not about audible RF, it's about how the RFI interference affects (effects?) a circuit...
Speed, the verb 'affect' means 'influences'; the verb 'effect' means cause.
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Shielding may or may not be important for you, depends on where you live and what airborne grunge is broadcast in your area. But please ditch the ferrite - that only chokes out dynamics.
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Personally I can't tell a flip of difference in my system. However, I did make shielded for my dac. :dunno:
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Speed, the verb 'affect' means 'influences'; the verb 'effect' means cause.
Ok, if we're giving grammar lessons, 'effect' is generally a noun not a verb. No offense intended, these have got to be two of the most commonly confused words in the English language. :lol:
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The thing here is the interference affects the circuit, but to the listener it may be somewhat like a sound effect.
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Ok, if we're giving grammar lessons, 'effect' is generally a noun not a verb. No offense intended, these have got to be two of the most commonly confused words in the English language. :lol:
I agree; the reason I offered my note is that Speedskater indicated he/she didn't know which was correct.
I VERY seldom offer grammar/spelling/usage corrections online--WAY too many of the semiliterate are proud of their ignorance and wish to remain so. Hence they resent anyone trying to educate them.
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The thing here is the interference affects the circuit, but to the listener it may be somewhat like a sound effect.
Not really...
The amount of noise to have an artifact literally means something is broken. I suppose it could sound like poor mastering, incorrectly used compression, etc... but noise never appears as something you could "put your finger on" in a properly working system.
Your earlier statement that you're hearing the affect of noise on your music is the best description. You don't know what the music sounds like without it, until it's gone. Even then you often have to listen for awhile and switch back to get a clear concept of what you were hearing because it's such a new form of understanding.
It's hard as ever loving hell to explain to a musician that there's changes to improve their gear, that can only make the type of sound they're making better... I'd venture to say maybe well above 90% can't conceptualize it. They literally won't even try because they assume it changes the type of sound, as to them the type of sound is the quality. I've found myself literally nearly banging my head on the wall wanting to yell at people over this because it's so infuriating that they're so god damn balless they won't even plug a guitar amp into a power conditioner... despite it being the most utterly amazing experience one can have with a power conditioner (ironically right after another group just did and loved it). Musicians are often some pretty unique snowflowers... and about as fragile as them.
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come on guys,the only way hum can get into a circuit is through a low level signal high gain circuit,these use regulated power supplies with very low hum ripple and seilded cables at the input(s) of the gain stages,there is no need to seild the power cable,just the signal cable of the gain stage usually the first one.
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come on guys,the only way hum can get into a circuit is through a low level signal high gain circuit,these use regulated power supplies with very low hum ripple and seilded cables at the input(s) of the gain stages,there is no need to seild the power cable,just the signal cable of the gain stage usually the first one.
Hum?
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come on guys,the only way hum can get into a circuit is through a low level signal high gain circuit,these use regulated power supplies with very low hum ripple and seilded cables at the input(s) of the gain stages,there is no need to seild the power cable,just the signal cable of the gain stage usually the first one.
George - While the shielding thickness practically implemented on either ICs or power cords is quite effective against capacitivly coupled RFI noise, isn't it too thin to be effective against inductively coupled mains hum?
(http://www.audiocircle.com/image.php?id=40268)
Skin depth vs Frequency
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come on guys,the only way hum can get into a circuit is through a low level signal high gain circuit,these use regulated power supplies with very low hum ripple and seilded cables at the input(s) of the gain stages,there is no need to seild the power cable,just the signal cable of the gain stage usually the first one.
Hmmm,
I thought you said you had left and made your last post...
http://www.audiocircle.com/index.php?topic=136527.msg1452003#msg1452003
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George - While the shielding thickness practically implemented on either ICs or power cords is quite effective against capacitivly coupled RFI noise, isn't it too thin to be effective against inductively coupled mains hum?
(http://www.audiocircle.com/image.php?id=40268)
Skin depth vs Frequency
From experience I havent had any problem with inductive rfi coupling quite the opposite with capacitive coupling high frequancy rfi,to combat this i use nfb with low freq. response in the gain stages...
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George- Its been a pleasure to have this one last 'who's on first' conversations. 8)
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George- Its been a pleasure to have this one last 'who's on first' conversations. 8)
It may not have been the last...
http://www.audiocircle.com/index.php?topic=136527.msg1452417#msg1452417
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I forgot to mention,if the RFI is inside (20hz - 20khz) the audio band,you must shield the cables internal/external and the circuit by putting it in a metal box and grounding it.
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Always confused regarding power cords. Why go bigger gauge than the wiring from your circuit panel to the wall receptacle (typically 14 gauge, sometimes 12 gauge)? Why shield when nothing from the power plant to the wall receptacle is shielded?
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Always confused regarding power cords. Why go bigger gauge than the wiring from your circuit panel to the wall receptacle (typically 14 gauge, sometimes 12 gauge)? Why shield when nothing from the power plant to the wall receptacle is shielded?
Power drills,smps,etc produce RFI in the audio band,they can get into the electronics in many ways,transformers do emit RFI in the audio band (100hz) ,in close proximity with a gain circuit this hum is in the audio band and the amp amplifies it,it's rather complex subject,but i agree with your point about house wiring being unshielded, interconnects shielding is a must
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Power drills,smps,etc produce RFI in the audio band,they can get into the electronics in many ways,transformers do emit RFI in the audio band (100hz) ,in close proximity with a gain circuit this hum is in the audio band and the amp amplifies it,it's rather complex subject,but i agree with your point about house wiring being unshielded, interconnects shielding is a must
Isn't interference in the audio band EMI; RFI being EMI at radio frequencies?
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Always confused regarding power cords. Why go bigger gauge than the wiring from your circuit panel to the wall receptacle (typically 14 gauge, sometimes 12 gauge)? Why shield when nothing from the power plant to the wall receptacle is shielded?
I agree with this, but I do see the value in an RF choke in the form of a ferrite collar around the power cord at the component end (this way both conducted and radiated RFI is absorbed).
I remember years ago Hi Fi News ran an article on the relationship between measured specs and sound in amplifiers and their conclusion was that the only measurable amplifier specs that bore any relationship to perceived quality of sound (beyond huge levels of high order harmonic distortion) were
1. the amp's response to RF contamination of the input signal and
2. the amp's recovery-from-clipping behaviour
This was in response to the confusion caused by the very-poor-measuring-but-exquisite-sounding Ongaku amplifier.
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all is electromagnetic waves,but i guess you right,radio frequency in some books refers to high frequency electromagnetic waves..
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Always confused regarding power cords. Why go bigger gauge than the wiring from your circuit panel to the wall receptacle (typically 14 gauge, sometimes 12 gauge)? Why shield when nothing from the power plant to the wall receptacle is shielded?
If your cables right after the wall do more attenuation of noise you've gained as the cable runs to the AC receptacle, you're winning. Also Romex is a good conductor, but too stiff for cables.
And bigger gauge means lower resistance which gives a potential for better attenuation.
Shielding might play a role since the environment goes from one cable to a lot in one area; which creates a noisier environment instead of one line with noise. The environment is interesting because coupling between separate conductors (cables, enclosures, etc) adds gain for RF, as the antenna is improved from length of conductors as they separate farther and farther out from a central point (typically).
The other things in your house affect your equipment by adding noise they're an antenna for, by generating their own, by changing Q to make your equipment less effective at attenuating noise (think mismatching impedance but potentially in a chaotic way), feeding common mode noise into the lines (every small transformer does this, think SMPS and cell phone charger etc), disturbing the power factor greatly, and especially screwing with safety grounds reference when it's daisy chained instead of star.
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I agree with this, but I do see the value in an RF choke in the form of a ferrite collar around the power cord at the component end (this way both conducted and radiated RFI is absorbed).
Except they usually make your stuff sound awful.
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Except they usually make your stuff sound awful.
That has not been my experience.
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That has not been my experience.
I can't tell you why, but nearly exclusively anything that removes RF is fine, except ferrite beads that 360* cover wire. I'm a huge proponent of CMC's, but ferrite beads? The definition of trying something over and over expecting different results... er I've stopped putting them on things despite thinking, "oh, maybe this time".
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interference can come from two directions,electromagnetic wave or electric current or both,electric current interference comes from the mains next to power supply next to amplifier input,luckely we can eliminate this by power supply filtering and decoupling before it reaches the amplifier input,if there is also electromagnetic wave interference in the audio band we have to shield the inputs this can happen if we dont use a mains filter/power conditioner in the mains,mains wiring without filtering will broadcast this interference as RFI/EMI as well as interference current in power supply because of unshielded mains wiring,this hasnt happened to me
but in high interference enviroments could,the other thing i want to mention is some designers have a choice,they shield the tranformer.others they shield the amplifier inputs,both achieve the same goal,while others they shield both,taking it to say extremes,for example i have use power amps with both unshielded inputs and transformers with very low hum,orientation of electronics and low gain is key here,twisted unsielded input wires are better than untwisted and fully shieled wires are better than unshieled twisted
twisted unshield wires provide some shielding because of the ground wire ovelaping the signal wire
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Heard a demo years ago at the Munich hifi show where they used power conditioning and then demoed shielded and unshielded power cables between the power conditioning unit and equipment. It was clear to my ears that pollution creeps back in when using unshielded power cables. If you're not using power conditioning then shielded/unshielded power cables probably doesn't matter imo. I don't recall what cables or equipment was used.
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Always confused regarding power cords. Why go bigger gauge than the wiring from your circuit panel to the wall receptacle (typically 14 gauge, sometimes 12 gauge)? Why shield when nothing from the power plant to the wall receptacle is shielded?
The heavier gauge is mainly for the power amplifier and to overcome voltage drop. To maintain the required power delivery to the speaker, the AC supply has to supply 1/0.25 (roughly) the current drawn by the power amp, which usually means larger cable. This is all to do with the operation of the diode bridge and capacitors in the front end of most if not all amplifiers.
There's more...power amps draw a reasonable noticeable non linear current from the AC which in turn creates harmonics from the original 60Hz waveform, the worst at 180Hz, 300Hz, 420Hz ++ and increasing multiples of odd orders of strength. These frequencies are in the bass region and are low enough to pass through filters designed at higher (Radio kHz) frequencies. If they modulate on the power supply in the amplifier, they can interfere with the music signal. Harmonics are included from the street and your neighbours, which doesn't help.
Depending on what type of power treatment is used and even the amplifier design, the good ones improve the bass response, since the designer has paid attention to these harmonics and although you can't remove them completely, suppressing them enough is about the best we could do.
You generally don't need a shielded cable for ovens, toasters, lights and washing machines. Shielded power cables for audio are designed to keep the (mainly RF and magnetic) noise out and what noise there is inside, is kept in. Problem for audio is that our ears can hear aberrations, that's why extreme measures are needed to plug up the holes so to speak.
For source components, a heavier gauge AC cable is not needed since the load drawn is small (<100W).
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Ok, if we're giving grammar lessons, 'effect' is generally a noun not a verb. No offense intended, these have got to be two of the most commonly confused words in the English language. :lol:
:D Is a "verb" a noun?
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Zombie thread alert!
Zombie thread alert! :oops:
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Except they usually make your stuff sound awful.
Awful is too strong a word.
They choke some of the bottom end usually. But, not awful. NuForce used to provide some beautiful power cords with quality chokes. I then switched to a audiophile shielded power cord and got a better sound. A modifier once told me that he demonstrated how the chokes effect sound at an audio show. Same cord. With and without the choke. He was the one who tipped me off on the effects on the bass.
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If marketing it results in more profits, the answer is always: yes!
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If marketing it results in more profits, the answer is always: yes!
I was informed its digital equipment that most benefits from shielding. Be that as it may, NuForce always provided a very nice cord with a choke. I believe NuPrime may have continued the same practice. Digital needs a bit extra help in that area. So far, I prefer shielding over a choke. But, I may learn otherwise over time. :wink:
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I was informed its digital equipment that most benefits from shielding. Be that as it may, NuForce always provided a very nice cord with a choke. I believe NuPrime may have continued the same practice. Digital needs a bit extra help in that area. So far, I prefer shielding over a choke. But, I may learn otherwise over time. :wink:
suppose the power of an amp is 40W
the current through the power cable is 40w/240v =166mA
most power cables are 10A
.166/10 x 100% = 1.6% is the amp current out of 10A cable
too much cable capacity is been wasted
now, a better cable will make much of a difference?
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It's more likely the digital or SMPS units are radiating the interference.
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Jim Brown writes on SMPS interference:
Switch Mode Power Supplies:
If you must use an SMPS, plan on adding suppression to it. Start with common mode chokes on both the 120VAC and low voltage DC lines for the frequency range(s) where you hear noise. Capacitors across the DC output terminals and the AC input terminals can also help. Select capacitors for low ESR (equivalent series resistance) at the frequency of interest and on the AC line side, use only type X1, X2, Y1 and Y2 capacitors, which are specifically rated for AC line use and designed to withstand the 3-6 kV spikes that can occur on power wiring. Choose this capacitor carefully – if it fails, it could catch on fire!
SMPS units tend to be noisiest at lower frequencies,
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suppose the power of an amp is 40W
the current through the power cable is 40w/240v =166mA
most power cables are 10A
.166/10 x 100% = 1.6% is the amp current out of 10A cable
too much cable capacity is been wasted
now, a better cable will make much of a difference?
You're looking at the wrong things possibly. Many will tell you how much better it sounds with an audiophile cable that was made well. I do not believe in spending hundreds of dollars. If it were not for Pangea power cords ( http://www.audioadvisor.com/products.asp?dept=25#filter:brand:Pangea$2520Audio (http://www.audioadvisor.com/products.asp?dept=25#filter:brand:Pangea$2520Audio) ) I would scoff at what some pay hundreds for. I would never bother to find out. And,I would have lived in an antagonistic attitude towards them, because they would be seen as toys for rich people.
But, I will tell you this. After seeing what a good difference they can make? It opened my mind to venture into things like simple fuses making an improvement. And, they can. Get the right combination, and they can transform what you hear in a surprising way. And, the most expensive do not have to sound better for your equipment.
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It's more likely the digital or SMPS units are radiating the interference.
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That is one valid reason why shielded cable can improve what you hear. I use a shielded cable on my audiophile computer. And, having one on a DAC can prove helpful. I just found that the most reasonably priced power cords are good all around, even for analog components. It just works. I am not concerned about scientific data when my ears tell me its OK. Now, those so inclined who are curious as to why it sounds better? I wish them luck. Even some folks running high end audio companies do not understand why they sound better. They just know they do, and can only offer theories as to why. The fact remains. They do sound better in many cases. And, they do not have to be ultra expensive.
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Chris Venhaus' rule of thumb is - use shielded power cords on digital equipment; use unshielded power cords on analog equipment. I think he bases this on extensive listening tests with his many designs. That seems consistent with your the above theories, though I suspect it's a YMMV situation depending upon system setup and how bad/good the power designs.
I swore by shielded ICs, but I've been slowly replacing them with unshielded ICs, just based on doing A/B listening tests, sometimes blind by asking a friend (or wife in a particularly patient mood) to swap them for me and not tell me which is which.
Side note on grammar - I'm somewhat over-educated, but I often do need to think twice about "effect" vs. "affect". Thanks jeffreybehr, that's the simplest most elegant explanation of the difference I've ever heard, at least for when used as a verb. I'd post that on my office cork board, but for the embarrassment, perhaps just a note in my wallet. I appreciate being corrected. My PPs are the constant misuse of "literally" and people using "may" when they mean "might" because "may" sounds fancier even though it's wrong, Just the other day I heard on the news about how so and so "may" die. Yeah, well we all "may" die. News flash, someone is not immortal.