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Myths and Snake OIL : Empirical Audio
Kan ikke si meg mer enig!
Uenig? (når en ser bort fra reklamen innimellom.)
Myths and Snake OIL
A number of audio cable manufacturers have sprung-up over the last few years that are intent on proliferating myths about the technical aspects of interconnects, power cords and speaker cables. Since the staff at Empirical Audio is technical-based, we would like to dispel some of these myths for our customers here.
Power noise and Power Cords
There are a lot of expensive high-tech power cords being sold in the marketplace these days. Many of these claim to improve the delivery of AC to components by: Shielding the conductors, providing very fine stranded conductors and other magical treatments. Also, some audio power outlets are made of exotic materials and have heavy-duty contacts.
The reality is that a power cord made from 12-14 gauge solid copper is pretty good. The problem with this is that this wire is not UL approved for cords and is very inflexible indeed. Most electrical Romex runs to the outlet in question are 20-40 feet in length. The power cord adds an additional 6 feet or so, so this is a small percentage of the entire run. It turns out that typical "rubber" stranded copper power cords have significantly higher inductance than the Romex in the wall, even at the same wire gauge, so these are not recommended. Empirically, stranded rubber cords have been demonstrated to limit transient high-power currents (dynamics) compared to solid copper conductors when supplying power to typical audio power amplifiers.
It is fairly easy to build a serviceable cable that will minimize power cord inductance. A simple 3-conductor twisted cable from 12 AWG solid THHN from Home Depot yields a very high quality power cord, although it is so stiff that it must be bent to the desired shape. It is actually superior to the Romex in the wall because the twisting and close proximity of the insulated conductors will reduce the inductance by magnetic coupling between the conductors. In the optimum configuration, the Hot and Neutral are twisted together and then the ground wire run beside or wrapped around them. The trick is to design a flexible version of this cord with the same characteristics. This is why some of the expensive cords are actually good designs, although more than $500 is unreasonable to achieve a good design.
The Magnum2 power cord represents a good tradeoff between cost and performance. It's inductance is extremely low, but it does not incorporate any exotic materials. It is flexible enough to replace a rubber cord as well. It sounds significantly better than the "Home Depot" cord described above, which is not bad. The Grand Slam power cord takes this to another level, incorporating Bare Wire Technology, improved dielectrics and ground-wire filtering (see the article below on RFI).
Unfortunately, most components do not have power supplies with sufficient energy storage and fast enough response times so as to not benefit from low-inductance cords. If the power supply in a given component has enough energy storage built-in with a low-inductance path to provide current to the electronics, then an improved power cord will have little or no effect. It is therefore primarily under-designed and inferior power supplies in audio components that will benefit from improved power cords. From experience, however, we have found that virtually all power amps benefit from a low-inductance power cord.
Power Cord Shielding
Shielding a power cable is unadvisable. It will add significant capacitance to the cable with minimal positive benefit. If you really need this, then the shield needs to be spaced well away from the conductors (large diameter) to minimize capacitance and avoid constraining the magnetic field lines that should couple between the conductors.
Empirical testing has shown that standard shielded 14 gauge stranded power cord sounds less dynamic than unshielded 14 gauge stranded cord when used with audio components that benefit from improved cords. The impedance of the AC electrical system is extremely low and susceptibility to magnetic and RF fields is extremely low for power cables so the benefit is questionable at best. Unfortunately, some of the commercially available shielded cords appear to make some systems sound better, but are actually "tone controls" for taming badly matched or designed components. There is some benefit to shielding if you are trying to protect unshielded nearby unshielded interconnects from the fields generated by the cord itself.
Better Power Outlets
Superior power outlets are another matter. Outlets that come stock in a home are usually cheap ones with push-in wire connections and 15 amp contacts. These are relatively resistive contacts. It is advisable to upgrade these to the screw-on wire types with 20 amp contacts. Hospital-grade accomplishes this, albeit at higher cost. Other improvements include high-copper-content outlets with silver or gold plated contacts.
It is always advisable to run dedicated heavy-gauge (8-12AWG) copper runs to power amplifier outlets, particularly in new construction.
Myths and Snake OIL : Empirical Audio
Kan ikke si meg mer enig!
Uenig? (når en ser bort fra reklamen innimellom.)Myths and Snake OIL
A number of audio cable manufacturers have sprung-up over the last few years that are intent on proliferating myths about the technical aspects of interconnects, power cords and speaker cables. Since the staff at Empirical Audio is technical-based, we would like to dispel some of these myths for our customers here.
Power noise and Power Cords
There are a lot of expensive high-tech power cords being sold in the marketplace these days. Many of these claim to improve the delivery of AC to components by: Shielding the conductors, providing very fine stranded conductors and other magical treatments. Also, some audio power outlets are made of exotic materials and have heavy-duty contacts.
The reality is that a power cord made from 12-14 gauge solid copper is pretty good. The problem with this is that this wire is not UL approved for cords and is very inflexible indeed. Most electrical Romex runs to the outlet in question are 20-40 feet in length. The power cord adds an additional 6 feet or so, so this is a small percentage of the entire run. It turns out that typical "rubber" stranded copper power cords have significantly higher inductance than the Romex in the wall, even at the same wire gauge, so these are not recommended. Empirically, stranded rubber cords have been demonstrated to limit transient high-power currents (dynamics) compared to solid copper conductors when supplying power to typical audio power amplifiers.
It is fairly easy to build a serviceable cable that will minimize power cord inductance. A simple 3-conductor twisted cable from 12 AWG solid THHN from Home Depot yields a very high quality power cord, although it is so stiff that it must be bent to the desired shape. It is actually superior to the Romex in the wall because the twisting and close proximity of the insulated conductors will reduce the inductance by magnetic coupling between the conductors. In the optimum configuration, the Hot and Neutral are twisted together and then the ground wire run beside or wrapped around them. The trick is to design a flexible version of this cord with the same characteristics. This is why some of the expensive cords are actually good designs, although more than $500 is unreasonable to achieve a good design.
The Magnum2 power cord represents a good tradeoff between cost and performance. It's inductance is extremely low, but it does not incorporate any exotic materials. It is flexible enough to replace a rubber cord as well. It sounds significantly better than the "Home Depot" cord described above, which is not bad. The Grand Slam power cord takes this to another level, incorporating Bare Wire Technology, improved dielectrics and ground-wire filtering (see the article below on RFI).
Unfortunately, most components do not have power supplies with sufficient energy storage and fast enough response times so as to not benefit from low-inductance cords. If the power supply in a given component has enough energy storage built-in with a low-inductance path to provide current to the electronics, then an improved power cord will have little or no effect. It is therefore primarily under-designed and inferior power supplies in audio components that will benefit from improved power cords. From experience, however, we have found that virtually all power amps benefit from a low-inductance power cord.
Power Cord Shielding
Shielding a power cable is unadvisable. It will add significant capacitance to the cable with minimal positive benefit. If you really need this, then the shield needs to be spaced well away from the conductors (large diameter) to minimize capacitance and avoid constraining the magnetic field lines that should couple between the conductors.
Empirical testing has shown that standard shielded 14 gauge stranded power cord sounds less dynamic than unshielded 14 gauge stranded cord when used with audio components that benefit from improved cords. The impedance of the AC electrical system is extremely low and susceptibility to magnetic and RF fields is extremely low for power cables so the benefit is questionable at best. Unfortunately, some of the commercially available shielded cords appear to make some systems sound better, but are actually "tone controls" for taming badly matched or designed components. There is some benefit to shielding if you are trying to protect unshielded nearby unshielded interconnects from the fields generated by the cord itself.
Better Power Outlets
Superior power outlets are another matter. Outlets that come stock in a home are usually cheap ones with push-in wire connections and 15 amp contacts. These are relatively resistive contacts. It is advisable to upgrade these to the screw-on wire types with 20 amp contacts. Hospital-grade accomplishes this, albeit at higher cost. Other improvements include high-copper-content outlets with silver or gold plated contacts.
It is always advisable to run dedicated heavy-gauge (8-12AWG) copper runs to power amplifier outlets, particularly in new construction.
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