Power Demystified Garth Powell 2621 White Road Irvine CA 92614 USA Tel 949 585 0111 Fax 949 585 0333 www.audioquest.
Contents Introduction AC Surge Suppression AC Power Conditioners/LCR Filters AC Regeneration AC Isolation Transformers DC Battery Isolation Devices with AC Inverters or AC Regeneration Amplifiers AC UPS Battery Backup Devices AC Voltage Regulators DC Blocking Devices for AC Power Harmonic Oscillators for AC Power AC Resonance/Vibration Dampening Power Correction for AC Power Ground Noise Dissipation for AC Power Appendix: Some Practical Matters to Bear in Mind I.
Introduction The source that supplies nearly all of our electronic components is alternating current (AC) power. For most, it is enough that they can rely on a service tap from their power utility to supply the voltage and current our audio-video (A/V) components require. In fact, in many parts of the world, the supplied voltage is quite stable, and if the area is free of catastrophic lightning strikes, there are seemingly no AC power problems at all.
• A typical AC wall outlet (A + A1 Inverted Phase) The only detectable readings we see above are the self-noise of the test equipment itself. It’s essentially zero. This audio sample sounds like nothing because it’s a sample and second inverted sample of the studio’s wall power. No difference equals no audio sample.
• A well-regarded audiophile power conditioner/regenerator and their premium AC power cable versus the wall outlet. (A + B Inverted Phase) ( need text description) Here we see a considerable difference. These AC power technologies are doing their job, and the signal you see and hear are those that are lost to signal coupling and masking effects without use of these AC power solutions. What you hear is very low in level at times, because you are hearing the difference.
• The Niagara 7000 Low-Z Power Noise-Dissipation System and Thunder AC power cord versus the wall outlet. (A + C Inverted Phase) Here we see a far greater signal difference. This is a more effective AC power solution. What you hear seems louder and fuller, because the AC power technology can preserve far more information. All audio files are native signal with zero composition for volume level.
These analysis charts are taken from the digital audio difference files for all three test variables (the wall AC outlet A, phase inverted file A1, and power products B, and C) figure 1. What’s significant about this type of test versus the noise reduction over frequency (common mode, ground, or differential mode), surge suppression, or distortion, is that a difference file is the only one that perfectly tracks what the product will do in a real-world audio system.
Of course, what you see with any premium AC power device is a sizeable difference, and with the Niagara Series products we see even more. This difference is represented as signal. It’s not about shaping the tonal color of the system or simply creating a mild euphonic effect, rather a substantial quantity of audio signal that will either be lost or distorted from circuit-coupled noise. Low-level signals are critical to audio reproduction.
power delivery device that will serve a system best is knowing the intended application. It would be unwise to assume that the AC power technology most appropriate for a factory or broadcast facility is also ideally suited for a home audio system. Additionally, engineering with circuit-design dogma is rarely productive (everything has its place and nearly every idea has some merit).
connected components (thus, it is sacrificial). These devices are quite useful in areas where electrical storms are common and the resulting damage to electronic devices is well known. Unfortunately, some of these devices do not give a reliable indication of having been either damaged or destroyed after one or more extreme power spikes.
sistors and valves that can withstand electrical spikes as high as 1000 volts, and certainly spikes of 300 to 500 volts peak. However, today’s audio systems feature many surface-mount electronic devices that can suffer catastrophic damage with as few as 3 volts across many of their electrical junctions.
AC Power Conditioners/LCR Filters AC power conditioners and/or LCR filters are passive technologies—there is no active switching and no amplification devices are utilized—and they will typically work over a wide range of conditions (100-265 VAC / 50-60 Hertz operation) without any conversion or circuit adaptation. These circuits are often combinations of three passive devices, represented by the letters LCR, where “L” is inductance, “C” is capacitance, and “R” is resistance.
to line induction, it raises considerably with frequency. The load impedance is subject to the same electrical conditions, but the current load is in parallel, and that becomes the overriding impedance. Since power amplifiers feature dynamic current, the impedance is variable with frequency. This is a problem with passive filters if they are not both tested and electrically damped for real-world impedance (and most are not…).
quarter octave away. The advantage (particularly for differential AC and RF noise) of a welldesigned impedance-compensated LCR filter is that it can be manufactured to handle vast levels of current without saturation or clipping, and, if properly executed, it can maintain at least some of its filtering capabilities for many octaves beyond any other circuit or design. AC Regeneration An AC regenerator is essentially an AC power amplifier.
Furthermore, an AC regeneration amplifier is potentially large, heavy, and, if it has sufficient power capacity for an audio system, it will generate a significant amount of heat. Amperage times voltage equal watts (and you’ll need a lot). A regeneration device such as this that could supply 10 to 20 amps RMS at 100-250VAC will be costly, large, and create considerable heat (relative to its class of operation).
In short, this is the ideal solution for an AC motor, but a questionable one for an audio component. AC Isolation Transformers This technology utilizes an AC transformer with close to a 1:1 inputto-output ratio (i.e., the input voltage is typically about the same as the output voltage).
Some AC isolation transformers feature symmetrical (center-tapped) or balanced outputs, while others do not. An argument can be made for a host of winding techniques, but so long as the isolation transformer has a faraday shield and grounding drain, it can filter or divert a considerable amount of RF and AC electrical noise that is common-mode (symmetrical) in origin. This noise dissipation technique is effective over many octaves from the audio passband well into radio frequency bandwidth.
less than ideal and will not be linear (consistent over many octaves). Without the aid of a properly designed impedance-compensated differential AC filter, this can create inconsistent sonic results from harmonic to harmonic, octave by octave, as the noise-masking effect is not reduced in a thorough and predictable manner. For a power amplifier, it’s a source of current compression. So, ideally, it would be utilized for common-mode AC power and RF noise dissipation for source components only.
cooler than the regeneration amplifier, but it will do next to nothing for linear AC and RF noise dissipation beyond haphazard, unpredictable loss from the circuit parts. Any AC power device that must be operated at a considerable distance away from audio system components is at a serious disadvantage because long AC cords are carriers of induced RF noise.
AC Voltage Regulators A voltage regulator simply adjusts or compensates for the incoming AC voltage, and supplies a steady, predictable output voltage for the system components. Some of the very best voltage regulators are actually not referred to as such. In fact, AC regeneration amplifiers are the very best regulators, as the output voltage is typically within a fraction of a volt of whatever the chosen output voltage is set to.
above 90 decibels. The other issue is that all AC voltage regulators create varying degrees of noise, which defeats what is most required to gain greater fidelity and resolution from your system. Granted, some may live in areas where the AC voltage is routinely so low they risk the system shutting down, but that is the exception.
what like a door buzzer, and can be quite annoying. If the cause of this magnetostriction is in fact a residual DC modulating the AC power, a series capacitive blocking device can be quite effective in reducing or eliminating this troublesome buzzing. Many of these devices have been sold as accessories with the claim that, if not addressed, the residual DC will do audible harm to the system’s components.
close proximity to one or more oscillator circuits. Quartz crystals and other devices may be used, but essentially these circuits radiate considerable RF noise or energy for a short distance from their circuit. This is precisely the opposite of what most component electronic engineers strive to achieve, as we do not wish to make RF noise and its distorting and masking effects even worse.
AC Resonance/Vibration Dampening Again, everything in high-resolution audio counts. Everything makes a difference. However, a common problem in the audiophile community is placing the greatest share of attention or care to an area that is responsible for contributing a mere 0.001% to any sonic consequences. Obviously, we know that resonance within critical audio circuits is an important topic, and this is a known science. The lower the signal level is, the greater the chance of distorting the audio content.
Power Correction for AC Power Power correction for AC power is a variation on an 80-year-old technology termed AC power factor correction.
When the amplifier’s power supply is required to release joules of energy to supply its amplification circuits with the necessary power for an audio transient’s massive peak-to-peak voltage swing, the condensers in the power supply are acting as a type of charge pump that has just been driven from a fraction-of-an-ohm impedance to nearly zero. Granted, this occurs only for a brief moment (say 10ms).
Ground Noise Dissipation for AC Power Sadly, about a third of the differential-mode (asymmetrical) noise and some common-mode noise can be found on the AC ground lead. Because the electrical service counts on this redundant electrical lead primarily for safety (even though the audio industry relies on it for far more), there are very few things that can be done to reduce ground noise effectively and legally.
When successfully utilized, Ground Noise Dissipation for AC power enables less grain, more signal, more air, and more dimensionality because a large contributor to the AC and RF noise masking effects has been reduced and controlled. Appendix: Some Practical Matters to Bear in Mind I.
Although not precise, here is a rule of thumb for calculating the average (RMS) current your system will draw, and the capacity you will require for a wall service tap or an AC power product. The source components, computer components, and video components are all constant-current devices. So, if you look at the specification page of your products’ service manual (typically available online from most manufacturers’ websites), you will find total power consumption at the rated incoming AC voltage.
If we are investigating a very efficient power amplifier (Class D, digital switching types), such as are commonly found in subwoofers, divide by 4: 16.67 divided by 4 = 4.17 amps. Always leave some headroom. If you have a 16-amp service, you would ideally have at least 10 to 15% headroom above the added total of all the component amperage calculations. So, for 16 amps, our upper threshold would ideally be about 13 to 14 amps total. II.
you trust. The polarity position with the greatest resolution and the least edge and grain is the correct one. Mark it, and go to the next cord until you’ve made certain they are all in correct polarity. During the listening test, be sure to swap the polarity on a phono preamp while listening to phono, not a digital source or vice versa, as that could render mixed results. III.
the optimal rating to half voltage, it will likely turn itself off or go into a protection mode. Yes, there are instances where the life of a part (such as an output valve/tube) might suffer a lower life as the heater voltage is too low, but that’s rare.
Index AC inverters p.17-18 AC isolation transformers p.15-17 AC Line, Neutral, & Ground leads p.11-12 AC polarity p.29-30 AC power conditioners/LCR filters p.11-12 AC power factor correction p.24-25 AC regeneration p.13-14, 17-20 AC resonance/vibration dampening p.23 AC surge suppression p.6, 8, 30 AC UPS battery-backup devices p.18 AC voltage regulators p.19-20 Ampere calculations p.28 Capacitance p.11-13 Catastrophic damage p.8-10 Common-mode noise p.11-17, 26 Constant current draw p.
AC difference file test equipment: The Difference test was performed at Bernie Grundman Mastering – Hollywood, California, U.S.A. C.D. (Redbook standard) is Al DiMeola, Paco deLucia, John McLaughlin “Friday Night in San Francisco” Columbia CK 65168 (track one–Mediterranean Sundance). CD transport DAC – Aesthetix – Romulus Eclipse (balanced analog output) A/D convertor – Lavry-122-96 Mk.
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