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ESX Q1202 Power Amplifier EVALUATION:

by Mike Kimm

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Inexpensive None that I know of
Feature packed



This amp is a beauty, and it is a beast.

When you first get this amp, two things strike you: how tall it is (3") and
how heavy it is (I almost dropped it when I first picked it up!).  This thing
has a massive heat sink, and a lot of internals that weigh a ton.  Now weight
is a non-issue when it comes to amplifiers, but this amplifier performs like a
tank, too.

The amp comes with an owner's manual, mounting hardware, and a fuse holder.
The owner's manual is very lengthy, telling about all the features of the amp.
I fished out first thing, of course, to see how this amplifier worked, and was
amazed at the flexibility that this amplifier provides.


feature #1: a kick ass crossover!  It is variable from 50-4.2kHz, HP or LP, 12
dB/octave Linkwitz-Riley slopes.  There are three settings for the crossover:
full-range, highpass, and lowpass.  When it's set to full-range, it has a set
of loop-through full-range outputs, when it's set to highpass, it has a set of
loop-through lowpass outputs, and when it's set to lowpass, it has a set of
loop-through highpass outputs.

feature #2-bass boost and gain, no tricks here.  The bass boost has a narrow
bandwidth at 43 Hz, 0 dB to 18 dB.  The gain is variable from 150 mv to 9
volts unbalanced, 300 mv to 18 volts with the ESX balanced line driver.

feature #3-synchronous bridging!  When you bridge normal amplifiers, one
channel is inverted, the other is non-inverted and you have a bridged
amplifier (simplified explanation).  However, there is always a gain tracking
error in the preamp stage, and that gain tracking error can result in an
imbalance, for example the right signal playing louder than the left one.  If
there is a gain tracking error and the amplifier is bridged, one side will
clip before the other, and therefore you're robbing yourself of some power,
not to mention that there will be more distortion on one half of the waveform
than the other.  The ESX uses only one preamp section (the left) when bridged,
so it escapes these errors.

feature #4-true mono mode!  It relegates all transistors into a single
channel, effectively making it a true monoblock amplifier, rather than a
stereo amplifier that's bridged.  This allows for an ultra-stable 1 ohm mono
driving capability, and should result in better sound quality simply because
there is no inversion in the process.

feature #5-high voltage switch!  If the true mono mode is engaged, this ups
the rail voltage so you achieve max power at 2 ohms instead of 1 ohms.

So if you want your amp to play a single channel and want to achieve max power
into 4 ohms, 2 ohms, and 1 ohm respectively, here's what you have to press:

to achieve max power into 4 ohms-synchronous bridging
to achieve max power into 2 ohms-true mono + high voltage
to achieve max power into 1 ohm-true mono

If two amplifiers are bridged together and linked, they can actually relegate
both amplifiers to a single channel!  This is complicated, though, I won't get
into how that works.

Anyway, the amp accepts up to #6 bat and grd leads, and #8 remote turn on and
speaker leads.  The terminals are very beautiful: amplifiers that cost twice
as much doesn't have these nicely-machined direct-insert set-screw terminal
blocks.  They're very pretty to look at and serve a nice function: it's one
less break in the connection.

The RCA connections and all the buttons and gadgets are located on the right
side, the terminal blocks are located on the left side.  The fuse is located
in an outboard fuse holder that is provided with the amp, it is a 60 amp glass

subjective SQ:

Great!  I would put it against any MTX, Rockford Fosgate, or Soundstream any
day.  The sound is CRYSTAL clear, and I mean that!  After my listening tests
were over, I even TRIED to make it pick up engine noise and alternator whine,
but no can do.  I ran the RCA's parallel to the power wire, I used a mediocre
grounding point, I set the gain at a point way too high, and the thing STILL
didn't pick up noise (in a '95 Jeep Grand Cherokee).  hmm.

This little tank has brutal output capability, too.  While I didn't have
access to a voltmeter and oscilloscope, it was easy to tell that this
amplifier was putting out more than its rated power (120x2 or 400x1 into 4
ohms).  It bottomed out 2 Rockford Fosgate Punch RFP-812's with relative ease:
that's 2 12" subs!  It also bottomed out a pair of MTX Thunder 5000 15's at 2
ohm mono (that's with true mono and high voltage on).  Wow, I didn't even
expect that much.

Not only does it have a lot of continuous power, it has a lot of clean
headroom too.  I'd guess about 2-3 dB worth, definitely enough to make the amp
seem louder than its rating, much like a Rockford Fosgate would.

I tested the amplifier on my DEI HF 3065's, and it bottomed them out too: big
surprise, I wasn't even running it at 2/3 power.  The sound was also crystal
clear in this case.

I then moved it on to a car that was set up more properly than mine, an '89
Camaro RS that I usually use for amplifier testing.  It is relatively easy to
do this: my friend only has a single sub, and the amps are pretty much easy to
swap, and he has a well-defined front stage: a pair of Cambridge Soundworks
5.25" components in sealed kickpanels (for any of you looking for a really
good inexpensive 5.25" component set, these are a good choice).  The sound was
very crystal clear once again, and when I turned the crossover on, there was
still no noise.

At about 1/2 power to 2/3 power, I noticed something I notice of almost all
amplifiers that cost less than $2/watt: a touch of coloration.  Although I was
a little disappointed, I guess I knew it all along: in this price range, there
will be no perfect amplifier.  Anyway, I noticed that certain voices started
sounding a little scratchy, and some classical instruments were sounding a
little hissssssssy at the beginning and at the end of the sounds.  However,
these characteristics are characteristics I have found in almost all
amplifiers, so in comparison, for all the other things it does perfectly and
for the relatively great sound quality it provides compared to others in its
price range, I have no misgivings about this amp.  Also, the sound does seem
very transparent until about the 1/2 power mark, so if you want to buy the amp
with twice the power you need, you will have tons of headroom, clean sound,
and you will still end up paying less for it than the average mainstream

Final Comments:

Wow, what an amp.