In the world of home theater and hi-fi products, there
are a lot of accessories that may or may not benefit you in the long run.
But, I assure you the temptation is there to spring lots of money on them
As this hobby develops, it seems the ability to just let things be
and leave the system alone diminishes at an exponential rate. The room that
yesterday you were ecstatic with now has a hint of something that may or may
not be a few placebos flying around. Either that or the night before you
dreamed of greater possibilities. This is continually fueled by the worst
unknown enemy of the enthusiast: the A/V forums. These forums will perpetuate
rumors, snake oil, and who knows what else until you drive yourself crazy
about how you just wasted all your money on something that appears to be the
worst product on the market.
Power conditioning falls into the accessory category but it may or
may not be an essential element in a home theater system. There are a lot of
heated discussions over how useful these things really are in the end
because of the fact that AC power is eventually converted to DC power in
your component and unless the power supply within that component is screwed
up, most if not all of the noise inherent in that incoming power will be
eliminated anyway. While this is true to a point, it is always better to feed a
power supply a clean, stable voltage to eliminate the possibility of noise
or fluctuations that may actually harm the products in your equipment
Balanced power is not a new design or approach in power
conditioning. It is a rather simple concept. In your home, the AC wall socket
that you normally use has three conductors: hot, neutral, and ground. Normally,
if you measure the hot to ground you should get 120 volts, and if you measure the
neutral to ground you should get 0 volts, but often, this is not what
happens, i.e., hot vs. ground might be less than 120 volts, and neutral vs.
ground might be 2 or 3 volts.
In a balanced AC circuit, hot vs.
ground, and neutral vs. ground will both read 60 volts. In other words, the
neutral conductors are both at 60 volts. Since these voltages are of opposite polarity though, and
given that most interference in a typical AC line is common between the two
lines, the noise in the lines is eliminated when the two lines are added
together. This is effectively known as Common Mode Rejection (CMR). You also
see this principle put to use in audio systems that use a balanced topology.
These are generally very expensive since these types of audio paths require
essentially twice the parts (complete paths for both the positive and
We have tested ExactPower products
over the years, and whether it was on the bench or in
subjective evaluation, they have proved themselves to be a valuable addition
to any system. Their initial units cleaned up the power, but it was not
balanced. So, ExactPower then added the SP-15, which was a balanced power transformer that
relied on a single transformer for all of its outlets. While this will
usually provide more power to a single outlet in use, it won't do as good of
a job eliminating ground loop hum that may come into play when you have a lot of
components connected to the same unit. For this review I received Exact
Power's newest balanced transformer(s), the SP-15Ax4.
The SP-15Ax4 delivers the same amount of total power
(1,800 watts) as the SP-15, but instead of using one large transformer, it
uses four 500 watt transformers that are completely isolated from each other
after the input stage. Each transformer supplies an individual GFI Hubble
outlet (each outlet has two sockets) for the best connection possible. Each of these outlets has reset
switch on it in case of tripping.
This is particularly useful for components
that may send a spike back into the power conditioner when you turn it on or
off. If this happens, that
outlet will trip and isolate itself from the others protecting the rest of
your components. I have used several components that have done this over the
years with the most recent being the Xbox 360. Whenever I try to plug this
component into the SP-15Ax4 it will trip the breaker on that outlet. A simple
reset (pushing a button on the outlet between the two sockets) fixes the issue, but at least I know that the rest of the components
connected to the SP-15Ax4 have been kept out of harm's way.
There are some drawbacks to balanced power transformers
in home theater applications, especially when you are using separate
transformers for each outlet. Since each transformer is only rated at 500
watts, you are limited in total output power for each outlet. ExactPower
states several times both in the manual and on the website that this product
is not intended for use with any big amplifiers or high current devices.
It is intended more for source components and digital devices such as
surround sound processors (SSPs), CD players, DVD players, and video processors. For
high current support, they recommend using their EP line of conditioners
(purifiers) that deliver 15 amperes.
In my configuration, I have an ExactPower EP-15A
plugged right into the wall with the SP-15x4 plugged into that. This gives
me line conditioning as well as balanced power, and essentially complete piece of mind with my
power. The only thing this duo does not offer is uninterrupted power via a
battery backup. While these are nice to have for PCs and display devices
that require cool down (bulb based rear and front projection displays), they
usually rely on an AC regenerator that is current limited.
I do not have my display connected
to the ExactPower package. It is on a
completely separate circuit that is supplying an outlet in my crawl space.
My power amplifiers are all connected directly to the EP15A, and all of my source
components and my surround processor are connected to the SP-15Ax4.
The SP-15Ax4 can be ordered with or without EMI
filtering. This is because the EP15 products already have EMI filtering so
it is not necessary if you already have an EP15.
The unit I received did not have the additional filtering.
before, each outlet is a premium grade GFI, 15 amp, isolated, full contact
Hubble NEMA duplex outlet. Trying to get a power plug into any outlet can be
a bit of a struggle as the connectors inside really clamp down. Trying to
get the power plug out is even harder. This is exactly what I look for in an
outlet. Cheap outlets tend to have play, and plugs can come out easy or
create a shock hazard by hanging out partially. The SP-15Ax4 can be ordered
with our without rack mounts and comes in silver or black finish.
Set-up of this unit was a breeze. The SP-15Ax4 is
essentially just a large box with outlets on the back. There are no special buttons,
meters, or displays to navigate. The front face is simply a milled piece of
brushed steel that is elegant but unobtrusive. There is a single power
button on the front panel with a power LED above it. Once you plug in
all of the components it will feed ,you simply turn it on.
After installation, the first thing I wanted to see is if the unit reduced
the noise coming out of my speakers with nothing playing. Regardless of what
I've used in the past, there was still a very small amount of low level noise
emanating from the tweeters of my speakers. I could hear it unless I put my
ear right to the tweeter, but it was there. The SP-15Ax4 completely eliminated
I suspect the noise was ground loop related. Since each
of the four transformers are completely isolated from each other, the ground
loop is interrupted.
On the subjective side I didn't really notice any real
change at all in the character of my sound or picture. Since I had been
using the EP-15 for some years now and since all of my equipment is on its
own dedicated circuit, I wasn't really expecting much of an improvement. The
SP15Ax4 did its job of isolating the components from each other and
eliminating any noise that the EP15 may not have taken care of already.
The GFI circuits did their part several times during this review. As
mentioned before, the power supply for the new Xbox 360 tripped the
receptacle a few times during my installation as did one of the video
processors I got in for review.
I was delighted with lack of noise from the speakers
during quiet music or movie scenes. Dynamics were slightly better than before due to the quieter
noise floor but since the noise was only slight originally, the difference
wasn't night and day.
I also noticed that the SP15Ax4
eliminated the noise produced by a light that uses a variable output slider.
This kind of light is notorious for introducing a buzzing sound in audio
systems. Since variable lighting controls are common in home theaters, you
can forget about that problem when using the SP15Ax4.
As with all power conditioning products, I
highly recommend evaluating your power needs before proceeding. However, the
chances are, if you live in a highly populated area (i.e., not on a 10,000
acre farm in the middle of Kansas), you probably have dirty AC power.
Something like the ExactPower SP15Ax4 can really help.
But you also have to remember that these products sometimes do even more
than clean up your power, they protect your components.
The combination of the EP15A and
SP15Ax4 represents an expensive investment, but every power issue I've ever run
into has been completely eliminated by having them. From dimming, noise, and trips, the duo
has eliminated them all. To this day, I don't think I've recommended a
product line more.
- Kris Deering -