[Occam]

George- Its been a pleasure to have this one last 'who's on first' conversations. 

[Russell Dawkins]

George- Its been a pleasure to have this one last 'who's on first' conversations. 

It may not have been the last...

http://www.audiocircle.com/index.php?topic=136527.msg1452417#msg1452417

[G Georgopoulos]

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.

[JLM]

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?

[G Georgopoulos]

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

[Russell Dawkins]

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?

[Russell Dawkins]

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.

[G Georgopoulos]

all is electromagnetic waves,but i guess you right,radio frequency in some books refers to high frequency electromagnetic waves..

[Folsom]

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.

[Folsom]

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.

[Russell Dawkins]

Except they usually make your stuff sound awful.

That has not been my experience.

[Folsom]

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".

[G Georgopoulos]

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

[birdlandthing]

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.

[One and a half]

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).

[Genez]

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. 

    Is a "verb" a noun?

[Elizabeth]

Zombie thread alert!
Zombie thread alert! 

[Genez]

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.

[JLM]

If marketing it results in more profits, the answer is always: yes!

[Genez]

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.