Some of them might be really useful and on some other they see to be as expensive gimmics. There are products like power filters, special power cables, isolation transformers, balanced power, power regenerators..
Here are some link to this kind of products:
Expensive power cords
Shunyata Research Anaconda Helix Alpha and Anaconda Helix Vx Power Cords
http://www.soundstage.com/revequip/shun ... llowup.htm
"The most naive and pedestrian view of power cords and their use in high-end audio systems is what I will forever label "the last six feet fallacy." This asserts that between your amplifier and power company there are miles and miles of power lines, so why on earth would the last six feet, which is what the power cord represents, make any sonic difference?"
The Anaconda Helix is a rotund 8-gauge power cord with 13 counter-rotating conductors braided into Shunyata's patented Helix geometry, which reportedly "dramatically reduces self-induced AC reactance while also providing exceptional immunity to RFI/EMI noise components." The Helix geometry is so complex that it has to be braided by hand. This, I am sure, accounts for the Anaconda's substantial cost: $1995 or $2195 USD.
Source: http://www.soundstage.com/revequip/shun ... llowup.htm
Do Hi-Fi Mains Cables Make Much of a Difference?
http://blogs.warwick.ac.uk/michaelwalfo ... -fi_mains/
"Cable companies are offering a range of power cables to the market place with prices seeming to go from about £35 for a QED one with Nordost Valhalla 2 metre mains cable coming in at just under £2,000!!!"
"Overall I still maintain a strong feling of scepticism. I guess if your system already cost many thousands of pounds then the odd couple of hundred quid as an experimnt is fine, however, for those of us in more real world situations I think getting better equipment after careful auditioning is the most sensible route to improved sound quality."
Sounding out the hi-fi 'kettle leads'
http://www.guardian.co.uk/science/2006/ ... nce.uknews
"Ok, hold on to your girlfriends, because this time we get seriously geeky. Last week we were talking about hi-fi company Russ Andrews, and their £30 power cable, which they reckon will improve the sound of your stereo. It's not a speaker cable, or a even a posh cable connecting your CD player to your amp. It's a power cable, from the wall socket to your hi-fi, a bit like a kettle lead."
"Now, interestingly, since last week, Russ Andrews have written in to explain how they believe their cable will filter out radio interference in the power supply, and so improve the sound of your stereo. Pay attention. They say their power cable has "a woven profile which takes advantage of the known effect of capacitive RFI cancellation of crossing wires, with the longer the cable and the more crossings in the weave, the more cancellation". Basically, what they are saying is the twists in the cable mean that it acts like an electronic component called a capacitor."
"What I want to know is: can you tell the difference between a £400 cable, a £30 cable, and a £1.50 cable, if you don't know which one is being used at the time? That is a double blind trial."
Balanced power
Balanced power FAQ
http://www.equitech.com/faq/faq.html
When 120-volt AC power is balanced, one side of the circuit has +60 Volts to ground while the other has -60 Volts to ground. (Across the circuit, the usual 120 Volts is still present. Fig. 1) A European 230 Volt balanced power system has +115 Volts and -115 Volts to ground on the conductors.
In a balanced power system, the voltages on the system's two output terminals are 180 degrees out of phase to each other with respect to ground. The system reference (ground) originates at the output center tap of an AC isolation transformer. In other words, the system's grounding reference (zero position) is located at the system's mean voltage differential or zero crossing point of the AC sinewave. This is a far more effective way to establish a reference potential for an AC system. The center tap is then grounded to Earth for electrical safety and for referencing shields.
Source: http://www.equitech.com/articles/rep1.html
Source: http://www.b-p-t.com/balanced-power-ult ... ators.html
Image source: http://www.transcendentsound.com/power_supply.htm
Power filters
An anti-RFI filter for the mains
http://www.tnt-audio.com/clinica/filter.html
"Everyone knows that a correct and clean power from the mains is a MUST for any serious HiFi system. Any electromagnetic interference that flows through the mains and reachs your HiFi system can unpredictably affect the overall performance of any component.
For this reason, during the last years, we've seen more and more power conditioners, line filters and similar devices starting to crowd the HiFi market.
Sometimes these devices are pretty expen$ive, even when they're nothing more than an isolation transformer (1:1) followed by a anti-RFI filter (cool down, I've said sometimes, not always
)""Here's the solution: you can buy a filtered IEC socket as the one in the picture above and change the old normal IEC socket of your HiFi components.
These filtered sockets have a small built-in ANTI-RFI filter that attenuates the intereferences ranging from 0,1 Mhz up to 150 MHz of an interesting 50dB amount.
The built-in filter usually has three caps and two inductances, everything being inside a sealed metal little box (the socket itself)."
Source: http://www.tnt-audio.com/clinica/filter.html
Russ Andrews Mains Conditioners
http://www.russandrews.com/category.asp ... JNWBWHSJPL
"Our mains filters reference to earth. For effective performance the socket they are plugged into should be earthed (‘grounded’). Conventional UK sockets are earthed; not all European and US sockets are."
Clarity Mains
http://www.russandrews.com/product.asp? ... JNWBWHSJPL
"Our ClarityMains™ unit utilises the incredible Coherence Technology™ that is a feature of our ClarityPro™ unit.
We've worked with the designers of the ClarityPro™ to develop a unit to fit inside our PowerBlocks and Ultra Purifiers to allow them to benefit from Coherence Technology™ - and the results have been so good that we've developed a stand-alone unit. Like our mains filter the Silencer, Clarity Mains™ is a simple, compact plug-top device designed to be plugged in close to your system. The noise reduction claimed by the manufacturers certainly seems borne out by our listening; even in Russ's system we heard a clearer, cleaner sound that seemed more dynamic. Use one or more in conjunction with our Silencers and Purifiers."
Source: http://www.russandrews.com/product.asp? ... JNWBWHSJPL
Quantum Mains Conditioners
http://www.russandrews.com/category.asp ... JNWBWHSJPL
"When it comes to describing what the QX2 and QX4 do it’s easy – they simply improve the musicality of your Hi-Fi. It’s when you try to explain how the Quantum Resonance Technology works that it becomes difficult. Hi-Fi Plus acknowledges this with their description of QRT as “…a field-generator based approach to mains purification that manages to confuse (on an intellectual basis) and impress (in terms of its unmistakable sonic impact) with equal ease.”"
MAINS POWER CONDITIONING & FILTERING
http://www.halcro.com/pdf/Mains_Conditioners.pdf
"These filter out radio interference signals from the mains (so
called "EMI" or "Electro-magnetic Interference.") which can cause
substantial degradation to the performance of many brands of amplifiers,
especially those which do not have appropriate circuitry to suppress such
interference. Thus such
filters may be of benefit to some brands. The Halcro units have extremely
extensive filters, both pre- and post- power supply, and in addition have
EMI suppression within the actual amplifier circuitry. Thus these units will
probably be of no benefit to the Halcro amplifier, but may well improve
source equipment (preamps, SACD players etc)"
Blocking Mains DC Offset
Blocking Mains DC Offset
http://sound.westhost.com/articles/xfmr-dc.htm
"A varying DC offset on the AC mains is no longer uncommon. There are many ways that a DC offset can be created, with most being totally outside the control of those who have to try to eliminate it, or put up with the mechanical noise created in toroidal transformers."
"It's also worth noting that DC is usually not a problem with toroidal transformers of 300VA or less. Their primary resistance is usually high enough that any DC will have little effect. With larger transformers (500VA and above), the DC resistance is usually so low that even a very small offset will cause mechanical noise due to saturation."
Power conditioners
Burmester Power Conditioner 948
http://www.burmester.de/english/product ... infos.html
"Burmester Audiosystems identified after some basic research a noise component in the power supply that is solely responsible for the sound deterioration. We measured a miniscule direct current of a few millivolts in the AC voltage. Not only was this DC component not supposed to be there it also varied it's strength over time. As it increased the sound of the system got worse. Available line filters did nothing to deal with this kind of line pollution. This is too bad because a few millivolts of DC are enough to drive amp transformers of any brand to the saturation point which becomes audible as transformer hum. As is widely known, the pure-bred transformers of high end-amplifiers are particularly susceptible to DC components in the power supply. "
"The Power Conditioner 948 measures the mean value of the supply voltage and adjusts it to zero by putting additional load onto the larger half-wave. In other words it assures that the voltage drop in the system is identical for the positive and negative half of the wave cycle. Hence, transformers no longer have to cope with direct current and stop humming.It is important to note that the Power Conditioner works in parallel with the connected audio components and thus avoids an undesirable damping of the voltage supply. This circuit logic is unique on the world market and has been patented by Burmester Audiosystems."
"A power supply corrected by the Power Conditioner provides the connected audio components with clean and even voltage. The result is a totally open sound."
"Many competing products try to keep line noise away from high end audio systems by stabilizing the voltage or synthesizing the supply system. However, this can easily compound the problem by destroying the low resistance of the voltage supply. Only a low-resistance system can supply large amounts of power in the shortest time. Higher resistance limits the overall power of the connected components. This leads to a limp bass reproduction, for example."
Power regenerator:
PS Audio Power Plant Premier
http://www.psaudio.com/ps/products/desc ... r?cat=powe
"The Power Plant is neither a conditioner nor a filter. In fact, the Power Plant does just what its name implies: generates new AC power just like the generating station powering your home right now."
"Our home’s AC sockets do not produce pure AC. In fact, what comes out of our receptacles is often distorted, noisy and at the wrong voltage. These distortions and AC problems result in poor performance for even the finest of equipment.
No power conditioner or filter made can fix these problems. What you need is a regenerator to build brand new power out of the original and that’s just what a Power Plant does.
This unique device rebuilds the AC in your home by first converting the AC to DC and then back again to perfect AC. Once rebuilt, the output of the Power Plant feeds everything in your system and provides regulated, low distortion sine waves from the AC wall socket; something no other power conditioner in the world can do. "
PS Audio Power Plant Premier
http://www.6moons.com/audioreviews/psaudio5/ppp.html
"To boot, the Power Plant Premier or PPP as the new concept has been christened delivers an ample 1500 watts of regenerated AC power. That's 50% more than its predecessor. Next, it puts out that amount of cleaned-up and regulated power with 85% thermal efficiency"
Source: http://www.6moons.com/audioreviews/psaudio5/ppp.html
MAINS POWER CONDITIONING & FILTERING
http://www.halcro.com/pdf/Mains_Conditioners.pdf
"2. Mains regeneration supplies. These in effect reproduce a regulated
mains supply and thus can be of benefit to amplifiers containing no
power supply regulation. The Halcro units are doubly regulated and thus
the use of such units will probably be of no benefit to the Halcro
equipment. Even though most source equipment has regulated power
supplies, these mains regeneration units may assist some source
equipment which are susceptible to mains current or voltage distortion."
Any comments on those electrical power products made for audio and hifi markets ?
