The sensitivity and sophistication of today?s electronic circuits require serious AC power conditioning. Anything less is too costly to consider, and will limit the performance our client demands.

Making a Case for Advanced AC Power Conditioning

Garth Powell | Furman Sound

Making a Case for Advanced AC Power Conditioning
by Garth Powell, Furman Sound

The sensitivity and sophistication of today's electronic circuits require serious AC power conditioning. Anything less is too costly to consider, and will limit the performance our client demands.



Isn't my plastic AC strip good enough for my electronic rack or cabinet?

My conditioner has a connected equipment warranty, so I'll never have power problems right?

I don't have any detectable hum, pops, ticks, or rolling bars in my video, so my AC power is OK, isn't it?

WRONG!

Today's electronic circuits are more sophisticated than ever, and their susceptibility to AC line problems is far greater.  Add to this the fact that today's AC mains supply is extremely noisy and the power grid is frequently taxed, and we have a recipe for component failure, or at the very least, poorly functioning equipment with unreliable behavior.

Most AC strips feature inexpensive surge suppression devices that are designed to "sacrifice" themselves when exposed to sustained over voltage conditions or transient voltage spikes.  Though they generally save the equipment downstream, the unit itself must be serviced.  Your system will be either non-operational, or at best unprotected until the damaged AC strip is replaced.  

Remember too that transient voltage spikes are not just present during lightning storms, your local power utility sends countless spikes through the AC wiring each week.  This is due to the necessary switching of one transformer or supply to another throughout the day to adjust for peak demand.  Though not as severe as a direct lightening hit, these voltage spikes have a devastating cumulative effect on most of today's electronics.  

Advanced Transient Voltage Surge Suppression

Audio / Video professionals can not accept down time, corrupted data, or unreliability. Today's home theater contractor, installer, or retailer shouldn't either. 

It is for that reason that a transient voltage surge suppression system such as SMP+ (series multi-stage transient voltage suppression with over voltage protection), is the best choice for critical Home theater - audiophile applications.  With SMP plus there's virtually no down time.  In fact, these circuits can typically handle multiple 6000 volt and 3000 amp pulses without sustaining any damage!  This is far beyond the demands placed on generic surge suppressors, but by constructing a circuit that is capable of this severe test, it ensures that equipment damage or maintenance is extremely unlikely.

One of the secrets in our SMP plus circuit is its ability to distribute or siphon-off much of the offending transient voltage spike, so that the power clamping devices do not have the burden of absorbing all of the energy and impact on their own.  Typical surge suppressors are like an outstretched spring with a bullet headed for it.  The key to our SMP plus suppression system is that the severity of the offending voltage spike is critically damped, so that the overall energy level is reduced to a fraction of what the clamping devices can handle.  So, like a well tuned shock absorber, the SMP plus circuit protects itself as well as the connected equipment.

Voltage Clamping Ratings

Another important concern for any surge suppression device is the rated clamping voltage.  The clamping voltage is the maximum amount of voltage that can pass through a transient voltage surge suppression (TVSS) system after the circuit has clamped and dissipated the incoming voltage spike.  This is an important point, because a clamping voltage that is too high will fail less frequently, but at the expense of component and system failures!

Since a large percentage of the clamping voltage rating will return through your component's AC cord (due to path of least resistance), and head straight for the power supply; it is mandatory that the voltage be in a range that the supply can handle.  For a 120VAC supply, the clamping voltage should be limited to approximately 200 Vpk.  That is roughly equivalent to 135 Vrms, which any component's power supply will handle without stress or failure.  Many typical SMP as well as conventional TVSS circuits may feature unacceptably high peak voltage ratings for their surge suppression, so it is important to note this when comparing.

Ground Contamination

Another consideration is Ground contamination.  Traditional surge suppressors and filters have leakage paths to ground.  This was considered acceptable for years, due to the ability of yesterday's active devices (such as valves and transistors), to withstand large short duration voltage arc-overs without a problem.  This is no longer the case with high speed surface mount integrated circuit chips.   In addition to the performance corrupting noise created by the AC voltage leaked to ground, damage to sensitive IC chips will occur over time.  This is because transient voltage spikes that are clamped by a suppressor device will deliver pass through voltage through the return, or common circuit path.  Since these ultra sensitive chip's ground pin is connected to the AC cord's ground wire, multiple transient voltage spikes can pit or fissure the delicate junctions in these devices. 

What does this mean?  Most surge suppressors may ultimately aid in the demise of your sensitive equipment unless the surge and filtering circuitry is entirely free of ground contamination.  Remember, your AC mains can deliver dozens of voltage spikes to your sensitive electronic components each day!

Sustained Over Voltage Conditions

Many surge suppression devices will not be able to protect equipment from sustained over voltages.  This condition is more dangerous and damaging to home theater components.  It can occur for multiple reasons.  A power pole may be damaged during a storm or accident, or in most countries (such as USA and Canada), lost or intermittent Neutral wiring of a multi-zone system can result in a sudden connection well in excess of 208VAC.  This will result in destroyed equipment, or at best, a destroyed surge suppression system.  In either event equipment servicing is required.

The one way to escape this problem is to insist on a surge suppressor - power conditioner with Extreme Voltage Shutdown, or run dedicated AC lines to each AC outlet.  E.V.S. circuits monitor the incoming voltage, and once the voltage has risen approximately 15% above nominal, they trigger a power relay to open, thus cutting the supply to all connected components and critical circuits.  Once the voltage is corrected, the unit is re-set, and operation may continue.

Filtering AC Power - Maximizing Home Theater Performance

In the past, AC filtering was considered a relatively small concern.  As long as pops crackle, or a local radio station wasn't picked up by your components power supply, filtering was sufficient.   This is no longer true.  AC noise is far greater in both amplitude and bandwidth than ever before.  When it couples into critical circuits it will mask and distort low-level information as well as create data corruption and losses.  This is due in part to the widening popularity of switching power supplies and the harmonics they back-feed into our AC power mains.

Today's power filters must have far greater efficiency, and cover a much broader bandwidth than ever before.  The filter should also be LINEARIZED. 

In the real world, sensitive electronics represent a complex load.  Unfortunately, traditional AC filter - conditioners have been designed for unrealistic laboratory conditions.  Prior technologies, whether multiple pole filter or conventional series mode, could actually harm audio and video performance more than help due to the resonant peaking of their antiquated, non-linear designs. 

Most traditional RFI / EMI filters are based solely on filtering or notching out specific radio frequencies at fixed impedance.  Far too often, this can create a noise attenuation curve that resembles a roller coaster.  Prior filtering schemes assumed impedances were constant, which is far from realistic.  Further, these designs did not anticipate high resolution audio and video components at the root of their design.  If noise reduction is non-linear and subject to strong ringing patterns that vary with load and dynamics, the AC filtering "cure" can be WORSE THAN THE DISEASE! 

A filter that is non-linear will sound and look discordant because of the way we hear and see.  You cannot lower noise in one octave (thereby unveiling far more information); only to increase the noise an octave away and, further, dramatically reduce noise ½ octave from there.  This is akin to a poor job of equalizing a recording, a bad loudspeaker cross-over design, or vivid reds and greens with horrible blacks and yellows in a video presentation.  For years, discriminating technicians have complained that many AC conditioners somehow "re-voiced" their carefully calibrated systems.  Indeed they did.  In the strictest sense, a 400Hz tone at 90dBa will be rendered unchanged regardless of AC noise, or the filtering system that's used.  However, a 10kHz signal that is occurring simultaneously at 70dB below the fundamental 400Hz tone will certainly be affected by AC noise that is induced 55dB below the 400Hz tone! 

Simply put, the AC noise that is coupled into your components' circuitry may be higher in level than much of the low-level signal it is attempting to reproduce.  If this occurs, a masking effect will certainly take place.  This is key, as high resolution audio and video is defind by it's ability to accurately reproduce complex low level signals! 

There are many other considerations for advanced power management such as Power Factor Correction, Uninterruptible Power Supplies and Voltage Regulation, but what must be understood is that the sensitivity and sophistication of today's electronic circuits require serious AC power conditioning.  Anything less is too costly to consider, and will limit the performance our client demands.


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