Product Review -
NAD 218THX Power Amplifier - December, 1996
By Daniel Long
USA: | NAD Electronics USA |
89 Doug Brown Way, Holliston, Massachusetts 01746 | |
Phone: 508-429-3600, Fax: 508-429-2426 | |
Singapore: | NAD Singapore Pte Ltd |
55 Genting Lane, Singapore 349563 | |
Phone 65-748-8918, Fax 65-748-9066 |
NAD 218THX Power Amplifier; Two channel power amplifier, power
output 200w rms/ch into 8 Ohms (225 w rms/ch for 120 V USA
version; all subsequent specs are for 230 V version only, check http://www.nad.com.au/product/amps/218.html for more details about 120 V version); Frequency
response 20 Hz - 20 kHz + 0.3dB; THD at rated output < 0.03%;
Input impedance 47kOhm, 700pF; Slew rate > 100 V/msec; Damping
factor > 200; Size 6 +" H x 19" W x 14 +" D;
Weight 51 pounds; US$999; UK: Phone 011-44-181-349-4034, Fax
011-44-181-343-3871.
Introduction
What's almost 10 pounds heavier, about the same size as
the NAD 208THX power amplifier, and differs by one character in
the model number? If you guessed the 218THX, you're right. The
208THX still sits on top of NAD's power amplifier range, and the
218THX is more conservatively rated at 200W (225W USA version)
into 8 ohms compared to the 208THX's 250W into 8 ohms. Also, when
bridged, the 208THX puts out a shocking 1.8kW of power
instantaneously into a 4 ohm load, while the 218THX is
"only" rated at 1.2kW. Lastly, the 208THX costs
US$1,699 compared to the 218THX's US$999.
So why the two "similar" models? I communicated with
NAD's Cas Oostvogel, and it seems although physically the 218THX
is bigger and heavier (due mainly to the size of the larger
"Holmgren" toroidal transformer), it puts out current
from a stiffer transformer, while the 208THX utilizes a dual rail
system. Hence, the 208THX is able to supply more current
instantaneously than the 218THX due to its more efficient design
and operation. Also, as you probably know by now (if you don't,
please go read the review of the 208THX which was published in
May, 1996, here in Secrets), the
208THX uses MOSFET output devices which are felt to sound more
"musical", although less powerful per device, than
bipolar-type devices.
Despite this, the 218THX's transformer weighs a very hefty 10.5kg
(that's more than 23lbs, about half the weight of the whole
amp!!) The 218THX uses a total of 8 capacitors (type not
indicated) with a total of close to 40,000uF (each 4,700uF).
Using 8 small caps instead of 2 large ones gives the advantage of
lower ESR (Equivalent Series Resistance) and ESI (Equivalent
Series Inductance), meaning a low power supply output impedance
and a faster recovery time; this, explained Cas, should result in
a better sounding amp.
Also, the 218THX's input stages are fed from a separate low-noise
regulated supply; together with a carefully laid out PCB and
"star" grounding, this results in a very noise-free
output. And as my auditions show, the 218THX is absolutely quiet;
no trace of irritating hum, even when used with the
sometimes-hummy Audio Alchemy DLC.
So you're out looking for an amp for that home theater and you
listen to music as well. Should you buy the 218THX or shell out
an extra US$700 for the 208THX? Hopefully, this more in-depth
look at the 218THX and how it compares with the 208THX will help
you with this decision.
Front
and Back
I must say the 218THX is about 30% more handsome than
it's more powerful brother (actually 29.74825% according to
calculations on my pocket sized Cray Computer). It now comes with
a pair of very muscular-looking handles. On the front are the
customary NAD LED indicators for Soft-Clipping Switch status and
Power. Below the vertical array of LED's is the power button;
when you power up the 218THX, the Power LED goes red initially
but flips to green when "all's well" is detected (i.e.,
no shorts, no faults). Accompanying this red-green transition is
something I like very much about the 218THX: the very loud and
re- assuring "CLICK" of the protective relays
dis-engaging. When I say loud, I mean it can be heard easily,
from at least 12 feet across a room with two noisy toddlers
screaming as loud as their lungs can pump out air (who needs an
amp?).
Moving to the back, you see where money hasn't been spent (I
hesitate to say "wasted" because that's a matter of
opinion) on multiple sets of expensive speaker binding posts and
the like. There are sets of balanced and unbalanced (RCA)
line-level inputs as well as one pair (per channel) of speaker
binding posts which take banana's or spades. Gone are the pair of
hinged flaps that many people disliked on the 208THX. When we
wired up the 208THX for comparison (my thanks to John Tan, an old
friend who's now the Asia Pacific Sales Director for NAD, for the
loaner), getting the speaker termination (in my case, banana's)
in was not a problem; however this left the flaps almost at a 90
degree angle to the rear panel, which is a pain if you haven't
got the space at the rear.
On the rear panel, you also get some slide switches for
balanced/unbalanced operation and Soft-Clipping on/off. I did all
the auditioning unbalanced (the input connections, not me!)
direct from my Audio Alchemy DLC, and I left the Soft-Clipping
switch off. My Mirage's M1090is were driven full range.
Music...
I used music that was quite dynamic first (this was also
to facilitate break-in, as Cas suggested the 218THX needs about
40hrs of it). Well, he's right. More about this in a while. Out
of the box, it was certainly very, very impressive, in that loud
transients were cogently reproduced, having all the impact you
could ever want. I used the Wilson Audio recording of "Winds
of War and Peace" on WCD-8823 (Lowell Graham conducting the
National Symphonic Winds) to determine if the 218THX could make
the Mirages' flex the solid hollow-block concrete wall behind my
listening area like my HSU sub can. With the HSU silent, the
218THX rattled my brains; I normally stretch my neck and lean the
back of my head against the wall during this particular passage
about a minute into track 1 (Liberty Fanfare). It didn't shudder
the room quite as convincingly as the HSU does when it's playing,
but the Mirages', driven full-range by my Audiolab, have never
done this (happens only when played loud, which the Audiolab
doesn't take too well to driving the Mirages' full-range).
On recordings with a strong and sustained bass line, the 218THX
never let the Mirages' do their own thing. It dictated
start-and-stop, especially of the four 6.5" woofers in the
pair of Mirages. And again, this didn't change when I turned up
the volume. It maintained this iron-grip as loud as I could
stand. This was apparent on recordings such as Mickey Hart's new
"Mystery Box" (Rykodisc RCD 10338), which is a fun CD.
This is a good "crank it up" recording.
When I tried something less visceral (like the last track O
Vazio, Tropic Affair on Reference Recordings RR-31CD) during the
break-in, I found the presentation ever so slightly forward
compared to the Audiolab. Images also tended to cluster in the
vicinity of the two loudspeakers, even on recordings that present
a very stable centrally placed image when reproduced by the
Audiolab. I also tried some pink noise, and this proved to be
slightly uplifted in the upper midrange and lower treble. Also,
though extended, the very top end (which I believe you may not be
able to hear, but instead perceive as airiness) tended to be a
little grainy, again compared to the modestly-powered but very
neutral Audiolab. This grain was apparent in that air didn't
sound quite like air reproduced by a more neutral amplifier but
instead sounded more like (slight) tape hiss.
This was present on most recordings. I decided to give the 218THX
more time with LOUD music...
and
Cinema
In the meantime, I watched movies with the 218THX again
driving my Mirages full-range. The usual bass-workout movies like
"True Lies", "Clear and Present Danger",
"Twister", "Seven", all took turns in the
Pioneer. Dolby Digital duty (DD or AC-3) was performed by the
Marantz DP-870.
Truly impressive is how I would describe the experience. Bass had
impact, effects were extremely startling if that was how it was
on the LD. And that scene from "Heat" (if you've
watched the movie, you know the ONE I mean!) If you've never
played this movie loud, you don't know what you are missing.
After the (long) shoot-out, you can almost smell the gunpowder
and see where the bullets went!
Even during the initial hours of my time spent with the 218THX on
movies, I noticed it's crisp upper-mids/treble, especially on
soundtracks that were so. However, as I logged more hours, I
thought it began to bother me less and less, until I hardly
noticed it. Overall, however, the 218THX's 200 wpc were extremely
valuable on demanding soundtracks, especially those with
aggressive Dolby Digital mixes. After getting through the initial
brightness, I was mostly caught up with what the 218THX did so
well, that of doing full justice to the intense bass- punch and
excitement of Dolby Digital soundtracks (mostly).
After
the Fire
When I went back to music on the 218THX after almost 2
weeks of movies with intense sound tracks, I found the
presentation still more forward than I prefer. However, that
brightness in the mids/treble was now hardly noticeable. Whether
I simply got used to it or otherwise, I can't say, but if I did,
then it must have been a minor problem and hardly one to detract
from the things the 218THX does right.
Compared
to the 208THX
I found the 218THX to be even more of a muscle amp than
the 208THX, which itself has earned accolades throughout the home
theater world for it's superb performance as a bass amplifier
(Tom Norton of Stereophile uses the 208THX to drive the enormous
Snell SUB-1800's). In my opinion, the 218THX is the 208THX and
more when it comes to meeting the demands of "here's my
invitation"- type sudden explosions! When I watched this
"True Lies" scene, the 218THX launched a wave into the
room that pushed me back into my chair and held me there for an
instant, something I didn't get to the same measure with the
208THX.
However, where the 218THX is firmly trounced is in the area of
subtlety, resolution and liquidity, especially with music like
the Golden String's original All- Star Percussion Ensemble. Using
the 218THX, you would concentrate on the clarity and accurate
reproduction of these percussive transients, and with the 208THX,
you would also marvel at the beauty of these different types of
instruments and simply enjoy the recording more. At the same
time, these instruments take on more of a "body" when
portrayed by the 208THX, and less that of a recorded entity.
Conclusion
For the money (US$999, S$1,350), I don't think you can
realistically expect much better than the NAD 218THX's
combination of high power control throughout the deep, mid and
upper bass as well as most of the midrange and accuracy from
there on upwards. It lacked the smoothness of the very best (in
my case, the Audiolab and NAD's own 208THX were the comparison
amps, so "very best" means them), but if you can live
with this, the 218 is tough to beat. So, I give the 218 a hearty
recommendation.
P.S. With regard to the 218THX's THX certification, this is only
true if the amp is used with bridging set "off" and the
unbalanced inputs are off. This contrasts with the 208THX's
certification even when bridged (don't know about the input
used).
Daniel Long
Singapore
© Copyright 1995, 1996, 1997
Secrets of Home Theater & High Fidelity
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