Recall that in last year, Garth Powell delved around topics filtering and isolation of AC power. On this occasion will talk about voltage regulation.

by Garth Powell *

So far I have written about the unique likeness of each professional electronic installation, is the live sound, broadcast on radio and television, sports venues, nightclubs or automated audiovisual systems for boardrooms: all depend on the power supply by AC (AC). In the previous two articles we discussed the peaks and transients AC, the danger of multiphase power supply with noise problems and intermittent AC neutral, ground loops and compression power.

Some of these issues are crucial for each installation, while others only become important when the application guarantees interest in maintaining the highest levels of quality. For example, if we are supplying power to a computer system for an office or for a scenario full of high-quality power amplifiers and mixing consoles, we must protect the equipment and make sure we do not lose our programming. There is a fundamental need to protect and filter dangerous fluctuations of current and noise that would affect the basic operation of our equipment.

Other control technologies AC power are more specific depending on the application. There is no doubt that a boardroom will have no problem minimize compression power in its power amplifiers, since the quality of the audio to a slide show or seminar transmitted over the Internet does not require the highest resolution (unless is the boardroom of a record label).

However, in this respect there is another common concern to all applications in Latin America: the AC voltage regulation. In short, a voltage regulator adjusts the AC input voltage and corrects abnormally high or low voltages, feeding vital components with a constant stream of 120 VAC. While the voltage may be of some continuously in some areas of their city, state or country, it is important to understand that most of the equipment you specify were created for a constant supply of 120 VAC. Still, the average voltage in Mexico, to cite one example, is 127 volts. Although located within 10% of the optimum voltage components, this will raise the temperature of the power supplies of many commercial electronics.

Some vital components may experience significantly greater distortions (unless all circuit parameters programmed from the factory to be recalibrated 127 VRMS). And 127 volts is just the average What happens in 130 or 136 volts? the operation is affected. Some teams will be blocked or intermittently overheat due to abnormal increases in line voltage AC. In addition, abnormal low of less than 112 VAC voltage raise similar concerns. It may present the same phenomenon and intermittent greater distortions. For example, some video projectors can not receive a consistent supply under these conditions reduced voltage.

Of course, for many people in Latin America, this is not a startling revelation. Many electrical contractors and designers have spent years audiovisual systems using AC voltage regulators. But many of these units are bulky devices to maintain basic appliances and incandescent lights, installed behind a standby generator. Electronic devices today require much cleaner technology and stable regulation. Overvoltage regulator grandfather, with burnt and rusty rusty electrical contactors and high impedance circuits, creates the same amount of problems trying to solve in the current sensitive electronic circuits.

Many regulators brownouts can cause shock, create noise AC, significantly increase the impedance of the AC (severely limiting amplifier performance), or simply fail to handle the demands of running your AV system uncut form wave of the AC and adding distortions that adversely affect the image and sound quality. This is equally problematic for current microprocessing technologies, as these require a stable and clean source of AC power to prevent blockages, digital errors and loss of information.

It should be understood that various technologies have been developed for different applications. Control technology more practical voltage for lighting your home is not necessarily required for your video server, and the system would be ideal for machines large engines is not what would best for a rack of power amplifiers. Of the many technologies voltage regulator that are in the market, the most common are:

  • ferroresonant: it is a complex circuit capacitance and inductance transformer modulated to create a substantially constant voltage and reduce noise asymmetric. The circuit is moderately expensive and can work well in some industrial or laboratory environments. Unfortunately creates heat, no tolerance for dynamic loads such as power amplifiers, emits a very audible hum and projects a magnetic field of several meters. For these reasons, it is not a control technology ideal for audiovisual professionals microprocessing circuits or computer systems.

  • Amplifier / oscillator complete regeneration: essentially this is equivalent to a power amplifier with large oscillator operating 60 Hz input. Take the AC input voltage, direct current makes it synthesizes and then again a source of AC with low distortion. The advantage is exceptionally strong regulation (generally ± 0,1 VAC). It also reduces the distortion of the AC line and eliminates some of the symmetrical AC noise. Unfortunately, this technology is inefficient and costly end. A simple output capacity 10 amps can be worth several thousand dollars, reheat a whole enclosure and create serious distortions compressions current or AC signal when the capacity is exceeded. It is ideal for AC synchronous motors, not for professional audiovisual equipment.

  • active correction lift / reduction: This design compares the AC voltage with a reference amplitude and controlled distortion, and adds or subtracts a correction to the AC input (with a maximum correction of ± 20%). The regulation can be very good (usually ± 0,5 VAC). It is much more efficient than complete regeneration to 100%, but may suffer from a serious limitation of current and AC create noise and distortion itself, partly due to the exchange of circuits that are commonly used. This technology might work well for some low current audiovisual equipment, but can be overcome by a autoformer several leads with solid state switching for its power amplifiers.

  • Motorized Variac: This design uses a autoformer lift / reduction with various derivations. On the surface above a cut autoformer are exposed coils which contacts a brush, creating the appropriate AC voltage, either raising or lowering the voltage. A microprocessor constantly monitors the input voltage relative to the output voltage, and moves the wiper motor accordingly. This technology has good regulation (± 1 generally VAC), but has the disadvantage that the engine emits a very audible noise when placed in an area of ​​audio. This technology was created for laboratories performing constant voltage readings.

Since the coils are covered with fat, and make contact with a brush, high current demands create sparks and noise in the AC line. The brush must be replaced and coils cleaned every one to two years. This makes the technology impractical for long-term use in most applications. In addition, the contactor creates a relatively high AC impedance, which seriously affects the power amplifiers. While industrial versions mass of this technology have been used for decades by some traveling professionals A / V (particularly when following a diesel generator and erratic voltage output) systems, low noise and ultra-high resolution today require much more of its energy source.

Finally, but by no means to forget, is my favorite technology AC voltage regulation for A / V professional, broadcast on radio and television, recording and boardrooms alike.

Autoformer switching zero crossing solid state with various derivations: this circuit works very similarly to motorized variac, except that as the microprocessor input and output (comparator) indicates the regulator circuit to raise or lower voltage. This is achieved by solid state switches with zero crossing. Since multiple switches are used, there is no exposed coils, and electrical contacts remain tight and secure for many years to come. The regulation can be quite good (± 3 VAC) with a reasonably wide capture rate (90 135 VAC-VAC). This circuit also has a control features exceptionally good transient compression with very little current. Unfortunately, the solid state switching can create some noise from AC if not precisely calibrated so that a good design without this noise can easily cost more than $ 700. However, if you have the budget, this is an excellent candidate for sensitive components today, even if they are subject to the most demanding environments.

Keep in mind that installations that depend on standby generators (gas or diesel) must be followed by a voltage stabilizer if you have a system that requires a corresponding voltage even at 120 volts. This is because the output voltage specifications of the generators are based on a constant current load. Does it look like any A / V system you have ever installed? Of course not. The result is that the current demand rises suddenly, the generator produces very little voltage and when the demand of low current, the generator produces too much voltage.

An AC voltage regulator is needed to control this. In addition, when a suitable AC regulator is combined with other energy control technologies, such as removing non-sacrificial surge and linear AC noise filtering, your system will be stable and secure, and your client will be well served.

*Garth Powell is a senior product designer and engineer sales chief Furman, a world leader in providing solutions for electrical control. It can be contacted at:

Many want to buy their first LED screen and do not know where to start. Here is a guide to the different products on the market with their advantages and disadvantages

by Adrian Morel

The decision to purchase an LED display is nothing everyday. These are expensive and there for various applications. Based on my experience, the entrepreneur who decides to buy a LED screen should analyze the following steps:

1. Study of Business: It begins with the idea of ​​knowing what the business, its utility, profit margin, etc. At this stage, the AV professional, more information on the display or the product itself, is looking for an orientation guide how to recover the investment. The AV companies begin to observe that almost all outdoor shows have LED screens and they can not be left out. This initial stage I call "study of business" because not even know about the financial possibility or viability of the investment.

2. ROI or return on investment: Here and mental decision to want to enter the business of the {mosimage} screens was taken and coldly analyzes everything about the return on investment, capital needs, searching for partners or associated companies, etc.

3. Decision to invest in screens outdoor o indoor: At first, the AV entrepreneur does not clearly differentiate between the use of outdoor or indoor screens, and for that reason want to find a shortcut, looking for a product that serves for both applications. If there is something we have to make clear is that the difference between a screen outdoor like a indoor it is as sharp as the difference between an Athenian centaur of a Cretan Minotaur, that is, two totally different things.

Invest in a screen pixel pitch also 6 mm for use in events outdoor It is like shooting a pigeon with a missile. The square meter of 6 mm screen is two, three or four times higher than the square meter of screen 16 mm and investment is very high for so little return. Ie use a screen event 16 mm outdoor It is leverage resources and have an adequate return on investment. For example, it is easier to get return to a screen that costs US $ 10.000 square meter to get return to a screen that costs US $ 30.000 square meter.

Many strive to have a screen low pixel pitch to please viewers who are on the front lines, but the truth is that these viewers, five meters away, prefer to see the singer with his own eyes and directly, not through a screen, because the screen is used for 20 row onwards.

4. Economic opportunity cost: At the cost of economic opportunity, the entrepreneur AVI should make their own numbers, confirm that your investment in screens will be higher than any other type of investment, for example, buy more projectors. Not only must analyze the cost, but must also consider the depreciation of the equipment, which for this type of products walketh in 5 average or more years. For example, the stadium of football team Seattle Seahawks has a LED screen 9 years and is in good condition.

5. Cost of the screen: You could say that is a determining factor in the decision, because at first glance, the cheaper screen is the most preferred. But make a decision based solely on price would not be smart, since it is just one factor in this equation 5 unknowns. Everything is interrelated: cheap screens provide a good initial investment but often require additional services or investments such as, for example, repair them short term and many cheap screens must discard after 2 years.

Indeed, the decision to buy a LED screen, is to adopt a particular technology and commit to a provider for the given time business life. After 5 or 7 years of use of the screen much water has flowed under the bridge and much of the provider needs in terms of after-sales services.

When buying a cheap screen should keep in mind if you are including provision of spare parts, training, technical support, customer service and convenient hours language for the customer, etc.

6. Duration: This point is clear, if you can choose between a screen that costs US $ 100.000 lasting in perfect condition 2 years and a screen that costs US $ 200,000 and hard 5 years, then the conclusion is easy: the second screen is slightly higher in service or cost-benefit ratio is more attractive.

7. Technology: This issue is complex because similar screens, with the same type of LED but from different vendors have different prices. For example, many compare an LED display using LEDs unbranded "believes" with an LED display using LEDs frontline also "believes" and look at different prices. For those who have never visited a factory of LEDs, I tell them that they have between 87 and 93 different quality levels. That is, a Cree LED with 5000 first selection and accurate NITs, has much more value (and more expensive) than an LED believed 4893 fourth selection NITs. LEDs having first selection makes the product, but ensures consistency and reliability over time. LED screens companies frontline LEDs only work with reputable and first selection.

8. Utilization:
The utility plays a fundamental role. If you buy a LED screen for fixed installation and puts on the floor number 21 to 500 meters away from the public, then the resolution of it is not as drastic as a screen that is close to the public where you can notice every imperfection.

In the case of Income screens, the construction of a road chassis is essential. For them usually they transported by land and require a more robust and resilient construction. For example, aluminum cabinets are preferred over steel constructions.

9. Service:
Customer service in Spanish is taken as a service, but it alone is not enough. Today we must also look to include service when we need it within three or five years, as many companies LED screens appear on the market every month, but few are projecting and endure over time. A company of LED screens that remained 10 years in the market, surely can provide service in the next 5 or 10 years.


The reversal of an LED display takes time, is expensive and must be associated with the correct LEDs provider screens. A good idea to get to know is to ask about the AV companies already established and have experience in the use of LED screens.

* Adrian Morel is CEO of Lighthouse Technologies for Latin America and can be contacted at his office in California (

This time the topics AC filtering, isolation and reduced power compression will be discussed

by: Garth Powell

Why the panel digital display system AV boardrooms crashes? How do I minimize whistling, ringing and white noise emission on our site, stage or recording studio? Our contractor A / V promised us the best picture and sound quality available. Why blurry horizontal lines that travel through our video screen presented? Why one of our sites presents emission clean and dynamic sound, but in the attached studio sound comes off and lifeless, no matter how ecualicemos or try the room? These are just some of the common problems that occur when a professional audio and video system does not incorporate a broad and advanced AC filtering.

Teams A / V today are more advanced than ever and that have electronic circuits that are highly susceptible to problems from the AC line. In addition to this, the AC current supply is extremely noisy and full of daily attacks pulse potentially harmful voltage transients, and we have a solution for poor component failures that presents an intermittent and unreliable behavior.

In our first article we discuss the problems with the impulses and transient voltage shocks and sustained surge and devastation that can cause current circuits based on microprocessing. In this article we will review the problems that can occur with an AC line noise and means to reduce them, and to optimize the performance of audio and video for critical applications such as professional studio recording and broadcasting.

Filtering AC Power

In the past, AC filtering was considered to be a relatively small problem. As long as the power supply components not pick noise or local radio transmitter, AC filtering was enough. This is no longer valid.

AC noise is much higher than ever, both in amplitude and bandwidth. When coupled in critical circuits, it is masked and distorted information and also creates low-level corruption, interference and data loss. For a broadcasting studio or concert venue to be supplied feeds studio quality signal, the digital era requires extraordinarily silent electronic circuits. AC noise goes against this, modulates the signal and significantly increases the internal electronic noise.

AC noise has increased, in part, by the growing popularity of exchange of energy supplies and the harmonics fed back into our energy AC. To counter this problem, the AC power filters today should have greater efficiency and cover a wide band wider than before. The filter should also be linearized (although sadly few are).

Most traditional AC filters are based solely on filtering or stepwise switching specific fixed RF impedance. Very generally, this can produce a noise attenuation curve that resembles a mountain range with many peaks and valleys. Before filtering schemes, the impedances were assumed constant, which is far from being real. In addition, these designs did not foresee the video and high resolution audio or computer components or DSP on the basis of their design. If noise reduction is not linear (irregular) and is subject to strong patterns of sounds that vary with load and dynamics, the "cure" AC filtering can be worse than the disease.

A filter that is non-linear sound and seem jarring by the way we hear and see, and noise reduction is inconsequential. You can not reduce noise in an octave (thus revealing much more information); It can be increased only noise one octave, and also dramatically reduces ½ octave noise from there. This is like a poor job of recording equalization, poor design convergence of speakers or the red and green bright yellow with black and horrible in a video presentation.

Isolation and correction of background noise

In addition to increased electronic noise and loss of resolution presented by the noise of the AC line, we must also worry about circuits background. Although rare small and moderate-time systems have this problem, larger complex installations may require multiple services to 15 20 amp, and if there are multiple paths background, it is likely that this circuit circuits fondo.Los background are usually the cause of the sounds heard on a loudspeaker or blurry horizontal lines are seen slowly up the video screen.

This problem is not only annoying, but it is unacceptable for his client or any professional installation. Unfortunately, without proper technology or AC wiring scheme this can be very difficult to repair. Background circuits are caused by a voltage difference between the earth and the line or the ground and neutral, and between one or more components. Ideally, each component of the system should be connected to a single AC conditioner or each component should be individually connected to a grounding (which should eliminate the problem), but that simply is not true for many installations.

The best way to repair or, better yet, to prevent this from happening, is to isolate the video that produces the problem and / or audio products at the level of the line with a transformer balanced isolation and high current to avoid currents circulating (or circuits background) -may otherwise.

In addition, this technology reduces AC noise to an even greater degree, enabling the highest possible resolution of audio and video components.

Elimination of current compression

Another unique problem for many theaters, radio and recording studios stations, is the use of massive power amplifiers with relatively inefficient loudspeakers. Remove all the dynamics, control, clarity and precision of their monitoring and audio playback requires a high power amplifier. The demands of the digital age have overloaded these systems to produce a much larger and equally bandwidth frequency much larger dynamic range, though the loudspeakers are generally less efficient than they were 35 or 40 years ago. This has been a considerable effort in high power amplifiers and active sub-speakers.

Unfortunately, massive power supplies can present overexertion amplifiers and current compression may occur. When an amplifier can not reach the maximum current that should be on demand, temporarily it becomes unstable. When that occurs, the system deteriorates the low speed, extension and control to be obtained from a superior amplifier and can no longer trust what is being monitored.

Instead of repairing this problem, many products of AC power management can actually compose this problem by increasing the AC impedance or resistance. This prevents the power amplifiers are auto-refresh with current up to an even greater extent and so many of the leading manufacturers of power amplifiers, high-performance sub-speakers powered recommend connect their products directly to the plug AC wall power, and prohibit the use of power conditioners.

One way to reduce this problem is making sure that power amplifiers possess an exclusive AC line not share your load current with other components or devices, and that the wiring is as strong as possible. An even better solution is to incorporate a power conditioner to AC Technology Factor Transient Energy. This circuit actually decreases high frequency AC impedance and offers both storage maximum current of up to 45 amp (for the duration of instability to 25mS).

What is achieved with this it is to ensure that even the most massive power amplifier operates with maximum efficiency. 100 watts per channel power amplifier sound as mono-blocks 300 watts more accurately, control and profound impact. The mono-block amplifiers 500 watts can earn between 5 7 and decibel dynamic range when this technology is used. Watts per channel does not really change, but the perception we have of how it should sound a power amplifier is directly related to its energy supply (and Technology Factor transient energy will cause the power amplifier to operate at Maximum capacity).

Energy Management: stopped being a convenience

Despite the best efforts made by a talented installer working with a qualified electrician, noise from the AC line is still a problem in many facilities of A / V. Proper cable management, the use of exclusive circuits and proper care grounding, are essential steps in designing an effective system. However, the higher resolution of the current content, combined with the exponential increase in noise in the AC line (before and after the power panel) and the deterioration of the power grid, protecting the point of use and filtering, currently are essential elements of any installation. Energy management should not be seen as an accessory or convenience, but as a necessary installation for all A / V component.

In the following article, we will discuss the causes and solutions to unstable voltage line (which is a big problem for installers in many regions of Latin America).

Garth Powell is senior sales engineer and product designer senior Furman, a leading global provider of energy management solutions. You can contact him via e-mail:



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