Unravelling the mysteries of your hi-fi / home theatre
Contents
1. Unravelling the mysteries of your hi fi home theatre system mains power supply revised Feb 2012 Jeandre Botha M Eng MBL 1 Why should I be concerned about my system s mains supply We live in an invisible sea of electromagnetic energy caused by the electronics we own radio stations the earth s movement through space even the sun s radiations Electromagnetic Interference EMI Radio Frequency Interference RFI and Electrostatic Interference ESI are on the rise with mobile phones wireless LAN s digital radio and digital satellite TV broadcasting all attacking your mains The arrival of 3G phones with their always live radio connections and wireless broadband internet connections introduces a hideous soup of RFI that your mains just love to transmit into your audio equipment All these signals when summed together in your living room are called EMI RFI or simply unwanted spurious electromagnetic signals or noise Ideally our AC power lines should contain nothing but absolutely clean 50 Hz but we don t live in an ideal world and our power supply lines are in fact massively contaminated In any city the degree of grid pollution is both large and ever growing EMI is conducted from audio components or appliances in your home via the AC power grid For example a humming refrigerator adds a lot of noise spurious signals on you AC power lines RFI is radiated by your system s components and cables and received from rad2. and thus degrade the amplifier s performance This is one of the reasons why Furutech does not design active power conditioners Power line filters that remove high frequency noise can benefit a power amplifier but transformers in series with the AC supply should be avoided An AC line conditioner that works with power amplifiers must operate in parallel with the amplifier that is they drain noise to ground without putting any electrical components directly between the amplifier and the wall outlet This is also Furutech s design philosophy for their AC line conditioners Also note that AC line regulation DOES NOT improve the sound of an audio system and can actually degrade it if the input voltage moves around the threshold at which a separate transformer tap kicks in Moreover most high end audio equipment is designed to work within the tolerances of the AC supplied by the electrical company This is why power conditioners for computers that incorporates line regulations should NOT be used for audio equipment A power line conditioner can t make poor audio equipment sound better instead it merely provides the optimum AC environment for those components so that they can realise their full potentials The sonic benefits of a good line Copyright AVCables cc Page 4 conditioner include blacker background with less low level grunge and noise The music seems to emerge from a perfectly quite and black space rather than a
3. circuit Additionally you re never alone your residential AC mains supply is shared with other apartments homes and businesses on the same utility transformer Because you re A V components have to compensate in real time to keep up and down with changing voltage they end up doing much more work and are often strained to accomplish the tasks they were designed for This can result in dramatically compromised system performance not to mention shortened component life The problems are numerous How can you tell you re a victim of polluted AC power Listen and look for these symptoms Flat hard grainy high frequencies a thick and bloated midrange fat uncontrolled bass and loss of air and soundstage stability On video displays the picture resolution is less than sharp with ghosting colour shift snow or vertical and horizontal lines If this looks and sound familiar you need to clean up your AC power Copyright AVCables cc Page 2 Fit p Se Nses vd ce your mind f 2 1 Video degradation that you can see Your TV monitor suffers visibly when AC power is unstable Unfortunately you may only realise this once you have installed a proper power filter and power cabling When you see the difference you ll know Regardless of which type or technology of TV display you own there s a power supply inside it that feeds the monitor with the electrical energy to display pictures at your chosen settings W
4. greyish background The treble often becomes sweeter less grainy and more extended Sound staging often improves with greater transparency tighter image focus and a newfound soundstage depth Midrange textures become more liquid and the presentation has an ease and musicality not heard without the conditioner If you haven t tried a power line conditioner you may not have heard your system at its best There are various manufacturers offering power cabling and passive power filtering distribution units as well as active power conditioners We at AVCables offer world class power cabling and high end power plugs and passive filtering distriobution units from Furutech For more information please contact the author or visit our website at www avcables co za FURUTECH This technical article was prepared by Jeandr Botha from AVCables CC He may be contacted on 082 774 4831 or visit their website at www avcables co za Copyright AVCables cc Page 5
5. hen your AC wall outlet supplies less than the required volts of AC power the power supply in your TV monitor has to work correspondingly harder to produce pictures at these levels The extra effort ends up being clearly perceivable as subtle and sometimes not so subtle picture artefacts such as flickering and noise as well as an overall loss of brightness contrast colour and sharpness In CRT based projectors this same problem will actually cause the picture to lose focus When the power supply works harder it burns hotter which then heats up the housings for the picture tubes When heated the tubes drift out of convergence and focus with the result being a fuzzier picture 2 2 Audio Degradation That You Can Hear The same problem clearly affects the audio in your system When a musical or sonic peak happens during a particular piece of music the amplifier s may need as much as 10 20 or even 30 times as much power for the brief moment of the peak This amplifier headroom is what gives your music the room to breathe sonically speaking When the amplifiers receive less than the 240 Volts of power from your wall that they were is your system cables ability to reject designed to work with they have to work much harder in order to or rather screen its conductors from produce the constantly changing energy for continuous musical signals Because the amp is all this noise that pretty much working overtime there s less e
6. hird a good line conditioner will reduce the amount of noise coupled to signal ground Finally AC line conditioners can protect equipment from voltage spikes lightning strikes and surges in the power supply voltage Not all AC line conditioners offers all the mentioned functions conditioners vary in their design principles with some addressing one problem but not another IMPORTANT Cleaning up the power line for source components and preamplifiers is a different job from condition AC power for power amplifiers Power amplifiers have very different AC requirements and thus must be treated differently The description earlier of what a good line conditioner should do applies to source components and preamplifiers that draw very little current Power amplifiers however draw enormous amounts of current from the wall When the power amplifier delivers a significant amount of current to the loudspeaker for a bass drum whack for example the amplifiers power supply reservoir capacitors are drained to supply the current The amplifier then draws a huge amount of instantaneous current from the wall outlet to replenish its filter capacitors The amount of current pulled from the wall can be so great that the AC waveform distorts under the amplifier s current draw the waveform s tops and bottoms are clipped off under the load Any isolation transformer or active line conditioner in the AC path could limit the amplifier s ability to draw current
7. io signals noise in the environment which is much worse in urban areas due to an accumulation of RF sources such as cell phones It s all noise and has varying negative affects on audio video signals ab 35 Household noise shown as accumulative series courtesy of Ecosse Reference cables 5K 10K 20K 30K 40K 50K GOK TOK 80K DOR 100K 110K 120K Mi Emaon Fans arc other What you are fighting in you mains system is not just one problem but a number of problems all of which have the potential to affect the sound and video quality of your system The first problem is earthing or rather a lack thereof The next problem is EMI and RFI as explained above As such dealing with your system mains supply should be considered fundamental Copyright AVCables cc Page 1 Fit if Se NSes mai Tee put mind f Thankfully electromagnetic effects such as capacitance inductance and resistance can be minimised by the use of high quality dielectrics Components and cables can be designed to reject RFI noise and proper filtering of your AC power and signal cables can reduce EMI conducted noise and the results can be heard if you have quality equipment PS There is also the problem of electromagnetic interaction between components across the mains but hey there s only 24 hours in a day for this stuff so read on and quickly 2 AC mains noise The facts Have you ever experienced days night
8. nergy to reproduce all of the fine details contained within the determines how your system is going to delicate audio signal being reproduced This problem perform naturally is compounded when the music or movie soundtrack calls for a dramatic sonic peak Typically for us audiophiles most noise occurs in the 5 to 80 kHz range right slap bang in the middle of our audible extremes Bastard Its your system cables ability to reject or rather screen its conductors from all this noise that pretty much determines how your system is going to perform Copyright AVCables cc Page 3 l Fie p Senses fi ce your mind ve 3 How do combat these problems 3 1 The AC Power Conditioner All of the above mentioned problems can be controlled with a well designed AC power line conditioner and screened power cabling Firstly nearly all conditioners filter the incoming AC line to remove the high frequency garbage generated by factories neighbours and your own household appliances Second some filters isolate the components from each other with small isolation transformers on some of the conditioners AC outlets These transformers break the physical connection between components preventing noise from travelling from one component to the other The isolated outputs are often marked digital for plugging in digital components preventing a digital processor from polluting the AC supplying the preamplifier for example T
9. s when your system just isn t sounding or picture looking as good as you remember it Something is wrong it s lifeless and uninvolving What s going on It s not your imagination It s because your AV components are designed to operate consistently with 240 Volts of AC power but they rarely receive that amount from your wall outlet The power is constantly changing and that s bad for home audio cinema There are many reasons for this Outside your home your local electricity provider o yep ESKOM is reacting to constant How can you tell you re a victim changes in consumer demand The higher the common demand in your community the less power coming of polluted AC power Listen and into your home Once inside your home the effect is made even look for these symptoms Flat worse Household appliances such as hair dryers the worst washin machines vacuum cleaner freezers i l hard grainy high frequencies a computer equipment etc compound the problem The AC power also thick and bloated midrange fat becomes severely distorted by other factors such as ground noise voltage spikes and sags high frequency uncontrolled bass power supply noise from other components in your own system plus radiated high frequency digital noise from processors and digital interconnects There are also distortion products at the top and bottom of the AC waveform created by switch mode power supplies in electronic devices on the same
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