Aesthetics /
specs / setup:
The ‘Sim’s’ as they shall be referred to
during the remainder of this review, are a
fully balanced differential mono-block
amplifier capable of producing 750 watts into
8 ohms and 1400 watts into 4 ohms.
According to the SimAudio website (www.simaudio.com)
the amp uses "technology featuring a no
overall feedback circuit and bipolar output
devices”.
Aesthetically the Sim’s are very handsome
and quite minimalist in appearance. They adopt
an integral framework, which provides both
lifting handles and spiked feet, allowing for
easy handling and lifting from the top of the
amplifier and at the same time negates the
need for a spiked amp stand.
The amps run cool and do not therefore require
hefty heatsinks as found on Krell amps, for
example. The result being a relatively light
and compact amp at a mere 71 LBS each.
The amps have both balanced and single ended
inputs, use a small nipple switch for on/off
operation, and disappointingly lack a second
set of speaker binding posts. Other than that
there isn’t much else to remark on as far as
aesthetics and connectivity are concerned.
Initially I used the amps with their integral
brass spikes into the carpet. This arrangement
doesn’t provide much clearance on the
underside of the amp and I was a little
concerned about ventilation. Coming from the
Krell MD300, I was half expecting a black
scorch mark on the carpet, but after an hour
or so of operation it was evident that these
amps run exceptionally cool. The main reason
for their relative efficiency is that the
design runs class A for the first 10 watts
only, thereafter switching to AB.
Having recently moved my system into another
part of the room, I no longer have a dedicated
amp circuit, so I have a less than optimal
arrangement with both amps pulling juice from
the same wall outlet. Pulling juice is
probably not an appropriate term for these
puppies, with a peak current rating of 85 amps
each, or 35 amps continuous, it’s more a case
of draining than pulling.
Sound:
Let me give a little background on the
decision to buy these amps. I’m using
Magnepan 3.6R speakers in quite a large room.
I’ve learned the hard way through extensive
trial and error that these speakers need gobs
of power to come alive. I wont list all of the
amps that I’ve tried, but 200w/channel Cary
V12 Monoblocks, Krell FPB200 and most recently
Krell’s MD300 monoblocks, have all been
through my system. Non of these so-called
‘muscle’ amps ever really got to grips
with the Magnepans in a way that could be
described as ‘authoritative’. Of course
the Krell MD300’s came closest, with their
650 watts into the Maggie’s 4 ohms, but they
always sounded muddy through the midrange, and
a little lacking in extension. So the Sim’s
on paper at least, seemed to remove any
lingering doubts of having sufficient power
on hand.
I had company on the day these amps arrived,
so I courteously offered Steve the sweet spot
for the first few tracks. The amps were stone
cold, having been sitting in the back of a UPS
van on a 20 degree day. They clearly needed
some gentle coaxing to get them up to room
temperature. However, with the amps cold, and
me sitting some 4 or 5 feet away from the
sweet spot, I could tell within the first few
notes that there was something special at
work. I could hear a warmth and depth to the
sound that no other amp has produced in my
system to date.
After 30 minutes or so of warm up, I assumed
position in the sweet spot, anxious to see if
my off-axis initial impressions were supported
from the critical listening spot. They were,
but with a small reservation or two. There was
tremendous depth and sweetness to the sound,
but with a slight smearing in the midrange,
and slight lack of clarity. This gave
instruments a slightly more homogenized sound
without a clearly delineated soundstage.
Listening to the instrumental track 3 on the
Ani De Franco’s Reckless CD, there wasn’t
the same attack, bloom and decay to the
acoustic guitar notes. It didn’t have the
impact that was evident with the Krell amps
that had just been replaced.
It was a little irritating to have this
apparent deficiency, but I tried to focus more
on the strengths that these amps clearly have
over the Krells.
I’ve never heard amps fill up the soundstage
like these do. A few days before they arrived,
I’d been experimenting with speaker
position, and moved them apart by almost 18
inches, to approximately 8’ between inner
edges. This seemed too much, and though there
was a nice sense of scale and stage width, the
leanness that the Krells had exhibited in my
system seemed to be exaggerated. With the
Sim’s in place, the soundstage became
completely populated without any apparent
leanness and with good center fill energy.
Bass was deep and tight. There’s a sense of
weight and authority that I thought was
probably max’d out when I added the Krells,
but the Sim’s provide more, and in spades.
There is also naturalness to the bass that I
haven’t heard before. Playing tracks from
the ‘Steve Green Trio’ CD, which is my
reference for the reproduction of acoustic
bass, the instrument sounded so tight and
defined, yet notes had all the bloom and
reverberation that you would expect to hear
from a ‘real’ and ‘live’ instrument.
I enjoyed this ‘new’ presentation for a
few hours then set about trying to correct
some of the weaknesses. I moved the amps off
the carpet and sat them on marble slabs, still
using the integral spiked feet. This seemed to
pull a little fullness and bloom out of the
midrange and tightened focus a little. Later,
I added large brass cones under the chassis of
each amp, effectively making the integral feet
redundant. This further increased focus and
added back the dynamic ‘snap’ and impact,
acoustic guitar strings now had that sense of
attack, bloom and decay that I’d missed with
the amps spiked into the carpet.
A week later, I removed the marble slabs and
used the large brass cones under the amp
chassis and into the carpet. The change was
subtle yet apparent and this arrangement so
far has brought the best results.
The top end of these amps is also excellent.
There is great extension and clarity, yet with
a sweetness to the sound that is generally
found in only the best solid state amps. I
have some room acoustic problems that need to
be resolved resulting in a slight glare at the
higher frequencies and a little ringing
through the midrange. But I have a sufficient
handle on those problems to know when it’s
the room and not the equipment. I don’t
detect anything in these amps that is anything
less than first class reproduction of sound,
across the frequency spectrum. The Krells
presented a tad more depth to the soundstage,
but this may have been a product of the leaner
midrange, when all said and done.
The Krells presented the stage level with the
front of the speaker and pushed it backwards.
The Sim’s present the sound slightly forward
from the front of the speaker and stretches
back almost as far as the Krell, so overall,
there is a greater sense of depth and 3
dimensionality with the Sim’s.
Bass performance was very good with the Krell,
but better with the Sim’s, the sense of
weight and authority is first rate.
The midrange is where the Sim’s really
excel. They provide a full, liquid and
coherent soundstage that fills up the space
between speakers providing a seamless whole.
The highs are clear and precise without
drawing unwanted attention in a way that can
quickly become fatiguing. There is an
excellent retrieval of detail, the subtle
information around the pluck of a double bass
string for example, is retrieved in a way that
I haven't heard before.
One small
discovery that has taken a couple of weeks to
appear, and has resulted in a very pleasant
surprise: the amps need to be powered up
continuously for much longer than I've ever
heard from another piece of equipment, before
they sound their best. I'm not talking about
hours, rather days.
I've had a
few comments from other Sim users on Audiogon
that have concurred with this. The sound of
these amps really starts to bloom after 3 or
more days of continuous AC. The soundstage
takes on more depth and detail retrieval is
improved quite noticeably. The downside comes
when experimenting with different power cords
or moving things around. You definitely loose
a whole degree of performance even with a 5
minute power-down, and it takes days for it to
reappear.
Summary:
These are by far the best amps I’ve heard in
my system. I can’t get enough music right
now, which tells me one important thing, these
are very musically engaging amps!
However, I believe that the full potential of
the Sim’s is not being realized presently,
due to my poor AC installation. That will be
rectified in the next week or so and I’m
hopeful for another step forward in
performance.
I would heartily recommend these amps to
anyone requiring extra weight and authority in
their system without losing any sense of
realism or finesse.
Rooze
| Type |
Solid
State |
| Configuration |
Mono |
| Power
Supply Transformers |
2
x 1kVA |
| Power
Supply Capacitance |
216,000µF |
| Class
Of Operation |
A/AB |
| RCA
Inputs |
1
pair (normal & phase
inverted) |
| Balanced
Input |
XLR |
| Input
Device Type |
J-FETs |
| Input
Impedance |
47,500
ohms |
| Input
Sensitivity |
1050mV |
| Output
Device Type |
Bipolars
- 20 |
| Output
Binding Posts |
WBT |
| Output
Power @ 8 ohms |
750
Watts |
| Output
Power @ 4 ohms |
1400
Watts |
| Output
Power @ 2 ohms |
2200
Watts |
| Frequency
Response |
10Hz
- 200kHz +0/-3dB |
| Output
Impedance |
0.005
ohms |
| Damping
Factor (static) |
800 |
| Gain |
33dB |
| Dynamic
Headroom |
6dB |
| Signal-to-noise
Ratio |
100dB
@ full power |
| Maximum
Output Voltage |
75
Volts |
| Slew
Rate |
80V/µs |
| Maximum
Current - Peak |
85
amperes |
| Maximum
Current - Continuous |
35
amperes |
| Crosstalk
@ 1kHz |
Not
applicable |
| IMD |
Unmeasureable |
| THD
(20Hz - 20kHz @ 1 watt) |
<
0.02 % |
| THD
(20Hz - 20kHz @ 750 watts) |
<
0.05 % |
| Available
Faceplate Finishes |
Black
and Silver |
| Power
Consumption @ idle |
48
Watts |
| AC
Power Requirements |
120V
/ 60Hz 240V
/ 50Hz |
| Fuse
Replacement - 120V |
10A
long fast blow |
| Fuse
Replacement - 230V |
5A
long fast blow |
| Warranty
(USA & Canada) |
10
years |
| Shipping
weight |
71
lbs / 32 Kgs each |
| Dimensions
(W X H X D) |
19
x 7.5 x 19 in. (49 x 19
x 49 cm.) |
Comments - Post your comments/views below!
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