valves via special transformers with bifilar
windings which needed only half the turns
ratio required by conventional output transformers. This meant that for the first time, a
consumer amplifier was able to deliver high
power, low distortion and a flat, extended
frequency response.
The Equipment
The MC2102 has a lot in common with the
original McIntosh, though it was designed and
engineered only recently by Sidney
Corderman who was called out of retirement
in 1997, having retired in 1993 after working
for McIntosh for 42 years. The clarion call
came because McIntosh wanted a unique
product to mark the occasion of the company’s
upcoming 50th anniversary in 1999.
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MC2102 TUBE POWER AMPLIFIER
equipmentreview
McINTOSH
M
McIntosh may not quite be the oldest name in
audio, but it’s certainly the most revered and
has been ever since Frank McIntosh built his
first amplifier, ‘way back in 1949.
The reason for its immediate success was
its Unity Coupled circuit design, which
McIntosh invented, and for which he was
granted a patent and which is still used in
the MC2102. The Unity Coupled circuit
made the McIntosh 50W1 one of the most
powerful consumer audio amplifiers in the
world at the time, but the real reason for its
success was that it had the lowest distortion
of any amplifier then available, and the
widest bandwidth.
All this was possible because McIntosh
had worked out how to deliver power from
both the anodes and cathodes of his output
AUSTRALIANHI-FI
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21
wound together) for a close, turnby-turn coupling. (Hence the name:
unity-coupled output circuit.)
The power transformer is tapped
for 100, 120 or 230V mains voltage,
so you can use the amplifier anywhere in the world. In-rush current
is controlled by thermistors, and the
power supply uses a combination of
four 1,000µF capacitors and a filter
choke to ensure smooth clean d.c.
The most visible features of this
amplifier are the two blue power
meters on the front panel. In fact
these meters (known as ‘blue eyes’
by McIntosh aficionados) are not on
the front panel at all—they’re behind
it, because the front panel is made
from clear glass. All the writing on
the front panel is etched onto the
rear of the glass. This is a very difficult way to make a front panel (it
takes three days because the glass is
cut using a high-pressure water jet
cutter and each of the 12 layers of
ink is UV cured before the next layer
is applied), but there’s a good reason, which is that the panel can be
returned to ‘as-new’ with just a
quick spray of Windex or any other
ordinary glass cleaner.
Almost as visible are the two
knobs on the front panel. The lefthand one controls the operation of
the output level meters and the front
panel’s backlighting (though why
you’d ever want to switch it off is
beyond me). The right-hand one is
the power switch (on, off, remote).
Like pretty much everything
McIntosh makes, these are highly
unconventional, because they’re not
regular switches. Instead, they operate solid-state electromagnetic
devices inside the amplifier which
do the actual switching. The switches are not dissimilar to the reed
switches used to connect doors and
windows to burglar alarm systems,
except that instead of using a permanent magnet to operate the switch,
McIntosh winds a coil around the
tube and uses d.c. current to energise the coil and create a magnetic
field which in turn actuates the
switch contact, opening or closing it
as necessary.
Although valve amplifiers don’t
really go into hard clipping like their
solid-state counterparts (one of the
reasons why valve amplifiers
sound better than transistorised
amps when they’re operated close
to their limits) McIntosh includes
an ‘anti-clipping’ circuit it calls
‘PowerGuard’. According to
McIntosh, this ‘provides real-time
clipping protection without affecting
power output or sound quality.’
The rear of the McIntosh is
unusual because for each channel
there are four WBT speaker terminals. Of these, one goes to the ‘negative’ speaker terminal, then you
choose one of the three remaining
terminals for the ‘positive’ connection, depending on the nominal
impedance of your speakers. There
are both balanced (XLR) and unbalanced (RCA) input connectors,
with a switch to choose between
them. The other switch on the rear
of the McIntosh is what’s used to
‘join’ the two channels together,
either in bridged mode or dual
mono mode, as discussed previously. If you choose the bridged mode,
not only does the power output
capability increase to 200-watts, but
also the minimum impedance the
MC2102 can handle drops all the
Corderman had joined McIntosh
fresh out of MIT. The amp he
designed was the MC2000
Commemorative Edition, which was
also a limited edition model, with
only 559 ever made. The amplifier
was so successful that Corderman
hung around to design the MC2102.
The MC2101 is rated at 100-watts
per channel but the channels can be
bridged, turning the MC2102 into a
200-watt monobloc. Actually, the
channels can be joined together two
ways, via a three-position slide
switch on the chassis next to the
input connectors (about which more
later). The three positions are Stereo,
Parallel Mono and Bridged Mono. The
MC2102 can be bridged to provide
200W mono into 16, 8, or 4-ohms, or
the two channels can be run parallel
to provide 200W into 4, 2, or 1-ohm.
In the mono bridged mode, there’s a
phase inverter dropped into the
input of one of the channels, so one
channel is 180 degrees out of phase
and the speaker is connected
between the two ‘hot’ output terminals. This gives a fully balanced
amplifier where the two output
transformers are essentially turned
into a single centre-tap unit.
The MC2102 has eight valves per
channel. Balanced input and inversion is handled by a pair of 12AX7s,
while twin 12AT7s provide voltage
amplification and driver functions.
Output valves are the famous KT88s (although you can use 6550s).
The output transformers have a
number of different taps, so they can
be matched to 2, 4 or 8-ohm loads
for stereo operation or anywhere
from 1 to 16-ohms as a monobloc. In
fact, the enormous output transformers make up most of this amplifier’s massive 40kg weight.
McIntosh still winds all its own
transformers in-house, using many
of the original machines (though one
suspects they’re as original as your
great grandfather’s axe). Remember
that to make these transformers,
three transformer windings are
required rather than the usual two.
There are two primaries (one for the
plates, one for the cathodes) and a
secondary. The two primaries are
spun bifilar (that is, two strands
McINTOSH
Brand: McIntosh
Model: MC2102
Category: Valve Power Amplifier
Suggested Price: $17,490.00
Warranty Period: Three Years*
Distributor: Castel Electronics
Pty Ltd
Address:
121 Beaufort Street
Preston
Victoria 3072
Tel: (03) 9484 3788
Fax: (03) 9486 3868
Toll Free: 1800 505 051
E-mail: general@castel.com.au
Web: www.castel.com.au
For additional information, turn to
page 114 and circle 0201 on our
Reader Information Service Card.
*Only one year warranty on valves.
equipmentreview
22
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AUSTRALIANHI-FI
way down to 1-ohm, a load that
would be the death of almost all
solid-state amplifiers. Oh, a note.
Be careful with these WBT terminals, because they have a ‘double
action’ thread, where the top nut
tightens on banana plugs and the
bottom nut tightens on cable or pin
connectors. If you don’t loosen the
top nut, for example, you won’t be
able to insert plugs at all!
A complaint that’s becoming
more common in audiophile (and
other!) circles is that ‘They don’t
make them like they used to.’
However true that statement might
be about many hi-fi brands, it
could never be said about
McIntosh’s products because basically they’ve been building them
exactly the same way for the last 50
or so years. While the company has
upgraded circuitry as better components have become available
(metal film resistors, polypropylene capacitors, etc) McIntosh has
made absolutely no attempt to
make its products ‘cheaper’. It
doesn’t even produce a ‘budget’
line, for example.
Just in case I’ve given you the
idea that McIntosh has been making valve amplifiers all these years,
I should disabuse you of this,
because it isn’t true. McIntosh
started designing and building
solid-state amplifiers almost the
minute transistors became available, commencing with the C24
preamplifier in 1964. Interestingly,
the company’s 1700 receiver, also
produced in 1964, was a hybrid,
but not the hybrid you’d expect. In
this receiver it was the tuner section that used the valves: the preamp and amplifier sections were
solid state!
It’s a source of some consternation to aficionados of McIntosh’s
valve designs that the current
McIntosh ‘look’ actually stemmed
from a solid state model, the
MC2505, which was the first separate solid state power amplifier
ever made by McIntosh. This amp
introduced the all-glass front panel,
the illuminated output level
meters, the Sentry Monitor circuitry and the McIntosh ‘autoformer’. I
photographs of the MC2102 show
this cage, because the amp looks so
great without it, and you don’t really have to fit it at all if you don’t
want to. I suppose it depends on
your home situation. If, for example, children are likely to have
access to the amplifier, I’d recommend ALWAYS using the cage.) My
understanding was that the KT88s
used in the MC2102 were made for
McIntosh by Svetlana (Russia) but
the ones in mine seemed to be
made in China. I love the sound of
KT88s (NOS rather than newly
manufactured), but if you’re a 6550
person, McIntosh is happy for you
to substitute.
McIntosh is not unaware of the
problem with heat, because in its
(absolutely excellent!) instruction
manual, it suggests you may care
to cut a hole in the table, bench or
shelf that’s supporting the MC2102,
to allow air to come up from immediately underneath the amplifier.
This is a great idea unless, like me,
you put the MC2102 on a polished
antique table! Needless to say, if
you’re one of those people who
likes positioning their amplifier on
the floor between their speakers, I
certainly would not recommend
this if your floor is carpeted.
When I was burning the MC2102
in (an entirely appropriate expression in this case!) I kept an eye on
the power meters, because the test
discs I use for burn-in have a wide
range of signals, and I was interested to see how accurate the meters
were, despite the fact that it’s my
personal opinion that power output meters on amplifiers are of
very little practical (if any!) use—
though I suppose they could alert
you to the presence of infrasonic or
ultrasonic signals. It seemed to me
that the meters responded very fast
and very accurately with tonebursts, impulses and pink and white
noise, though I didn’t have access
to any test equipment to verify the
exact speed of the needles, or the
calibration accuracy of the meter
markings. I’d have to warn that the
accuracy of the meters would also
depend to a large extent on the
speakers you use, and the particu-
should confess at this point that
this amp was also the first
McIntosh I ever experienced (I
regret to say that I couldn’t afford
to buy it.)
Listening Sessions
My McIntosh MC2102 came in
its original shipping package, so I
had to get it out myself (which
revealed to me—and my chiropractor—that it’s really a two-person
job!) and then plug in all the valves.
Generally, I’d imagine that
McIntosh dealers will deliver and
install the MC2102, so you won’t
have to worry about this, but if you
do, can I recommend you don’t
handle the valves with your fingers? It doesn’t matter if you do use
your fingers (otherwise dozens of
valves I’ve replaced over the years
would never have lasted as long as
they did) but you’ll find that if you
do, you’ll get fingerprints on them
that could be hard to shift after the
valves have heated up.
It’s often recommended that you
use white cotton gloves (and
indeed McIntosh provides a pair
for you), but I find these can be
slippery, making it tricky to grasp
the valve without running the risk
of dropping it. I used a new, dry
‘Chux’-style dishwashing cloth to
grab mine. Just to be on the safe
side, I’d install all the valves while
the MC2102 is still on the floor
(preferably carpeted) so that if you
do drop a valve, there’s no chance
of a breakage.
I am quite used to valve amplifiers running hot, which is nothing
less than you’d expect, particularly
if, like me, you’ve owned a few in
the past, but I found that the
MC2102 was like a small furnace! It
turns out that the eight KT88s are
driven with fixed bias, and because
of the cathode arrangement, each
one is driven by about 170-volts.
When you factor in the added heat
from the four 12AX7 input valves
and four 12AT7 valve drivers,
you’re looking at quite a handwarmer. After only a few hours of
operation, the metal cage that protects the 16 valves became almost
too hot to touch. (Actually very few
LAB REPORT
Readers interested in a full
technical appraisal of the
performance of the McIntosh
MC2102 Power Amplifier
should continue on and read
the ‘LABORATORY REPORT’
published on the following
pages. All readers should note
that the results mentioned in
the report, tabulated in performance charts and/or displayed using graphs and/or
photographs should be construed as applying only to the
specific sample tested.
AUSTRALIANHI-FI
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23
lar transformer tap you choose to
drive them. I guess the problem for
McIntosh is that it’s been fitting
them for so long that they’ve
become almost a trademark for the
company, so that a McIntosh
wouldn’t be a McIntosh without
those ol’ Blue Eyes!
Having owned a few valve
products in the past (Williamson,
Quad, Audio Research and, most
famously in my youth, two Lenard
valved musical instrument amps
wired as a high-power stereo!) and
had a McIntosh on long-term loan,
I was looking forward with intense
anticipation to hearing this new
McIntosh, so much so that I didn’t
burn it in for my usual length of
time because I literally couldn’t
contain myself, so keen was I to
hear real music. When I did, I
entered seventh heaven, because
not only did this new McIntosh
have the exact same classic
McIntosh sound I remembered
from years ago, it also had that
magical ‘valve’ sound!
What is the magical valve sound?
I don’t think I’ve ever seen it put
into words in a way that made it
understandable, so I’m reduced to
saying that for me (and for whatever
reason), music seems to sound more
relaxed and easy to listen to than the
same music through a solid-state
amp. The bottom line, I guess, is
that it’s more enjoyable. The music
acquires a special warmth and
depth—more so from LP than from
CD, it must be said, but it also gives
CD sound a lustrous ambience that
eludes the solid-state brigade—even
those using supposedly ‘valve-like’
devices, such as MOS-FETs. The jury
is out on why valve amps sound so
good. Some say it’s the inherent distortion, some say it’s the microphonics, some even claim it’s all an auditory illusion (can’t believe this last!).
All I can say it that if it sounds this
good, who cares?
However, the best is probably
yet to come because I also have to
tell you that the McIntosh MC2102
did not exhibit most of the limitations that most people claim affect
valve amplifiers. For example,
some say valve amplifiers sound
‘soft’ because their frequency
response rolls off early. There was
absolutely no evidence of this with
the MC2102, because the treble
sound was smooth and extended to
well beyond audibility, and that
was even when playing DVD-A
and SACDs using extended-bandwidth speakers. As for microphonics, I couldn’t induce any microphonic effects, even when I placed
the amplifier directly in front of the
speakers and turned up the volume
to ear-shatteringly loud levels. And
when I say ‘ear-shatteringly’ loud, I
suspect I’ve telegraphed the fact
that the McIntosh doesn’t have any
power limitations either! The volume just seems to go up and up …
and up. In the end, I hooked up my
most inefficient speakers, donned
some hearing protection (30dB
attenuation) and deliberately overdrove the MC2102. The sound didn’t become rough; it didn’t even
begin to sound strained—it just got
louder and louder. Eventually I
stopped only because I feared for
my loudspeakers.
I can’t conclude this review
without a short comment on valve
life, because the modern generation
of electrical engineers, many of
whom have probably never seen a
valve in their life, always seem to
overstate their fragility and understate their service life. You can get
the best idea of the robustness of
valves when you realise that most
guitar amps still use valves, and if
you’ve seen roadies loading and
unloading band equipment, you’ll
know they get some pretty (very!)
rough handling. Since the valves in
a guitar amp can withstand being
loaded and unloaded three or four
nights a week, every week, for
many years, the valves in a hi-fi
amp are obviously living the life of
Riley, by comparison. As for
longevity, think along the lines of
not hundreds of hours, or even
tens of hundreds of hours, but
upwards of eleven thousand hours.
That’s five hours a night, every
night, for more than five years,
after which you just replace the
valves yourself in a few minutes if
it’s necessary (and it may not be—
valves have been known to last
much, much longer. I once inherited some valves—still working—
from an amp my father-in-law had
built in the 50s, and used them for
nearly ten years!)
Conclusion
When pondering how to sum up
my feelings about this McIntosh, it
occurred to me that there are some
readers who will imagine that asking a valve amplifier buff whether
he likes the MC2102 is a bit like
asking a woman whether she’d
fancy a Cartier necklace, or a performance car freak whether he’d
like a Ferrari, at which point I suddenly realised that all three purchases have something in common—and I’m not talking about
the obvious! With all three, you’re
buying a slice of history; something
that will endure. The MC2102 is
valuable, in the true sense of the
word. It will be handed down to
your children, and your children’s
children. More important (at least
for you) is that every time you
switch it off after an evening of
musical pleasure you’ll know you
made the right decision!
Andy Brown
McINTOSH MC2102 TUBE POWER AMPLIFIER
AHF
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AUSTRALIANHI-FI
Test Results
Australian HI-FI Test Laboratories
ran two sets of power output tests
using different transformer taps. As
expected, the McIntosh MC2102
returned the best performance
(which was in excess of its rated
specifications) when the tap value
matched the impedance (or rather
in this case, resistance, seeing that
the lab uses high-power non-inductive dummy loads). The results
have been tabulated in the appropriate tables, but you can see that
into 8-ohm loads, using the 8-ohm
tap, the MC2102 delivered more
than 120-watts continuous per
channel with both channels driven,
and around 130-watts per channel
continuous with just a single channel driven. When the resistance
was dropped to 4-ohms on this
same tap, output increased with
just a single channel driven to 161watts at 1kHz and 147-watts at
20Hz, but the protection triggered
with a 20kHz test signal. With both
channels driven, the MC2102 delivered 118-watts per channel at 20Hz,
136-watts per channel at 1kHz, and
the protection triggered again
when the amplifier saw a 20kHz
signal. This means that in practical
situations, where the impedance of
a speaker at 20kHz is likely to be
higher than 8-ohms, you’ll get the
benefit of high power at low fre-
Strange but True
When Apple Computer developed its ground-breaking
Macintosh computer, it didn’t
want any legal stoushes complicating the launch, so it entered
into a license agreement with
McIntosh which ran for 10 years
and allowed Apple Computer to
use the Macintosh name in connection with computer products.
Apple decided it should do this
even though the two products
were not only not related, but
weren’t even spelled the same
way. Apple even paid McIntosh a
license fee, although the amount
has never been disclosed. Take a
look around the back of a
Macintosh Plus and you’ll see a
label that says: ‘Apple and the
Apple logo are registered trademarks
of Apple Computer, Inc. Macintosh is
a trademark of McIntosh Laboratory,
Inc. and is being used with express
permission of its owner.’
quencies, but the protection won’t trigger at higher frequencies, even for the same power level.
The power output results for the 4-ohm tap
show that if you use 4-ohm speakers, you’ll get
128-watts per channel, both channels driven, at
low frequencies, decreasing slightly to 123-watts
at 1kHz and 115-watts at 20kHz. (Note from the
dBW column that the spread is a mere 0.4dB!).
With 8 ohm speakers, the mismatch has more
effect on power output than when mismatching
4-ohm speakers to the 8-ohm tap, such that power
output drops to around 90-watts continuous.
Note, however, that the protection doesn’t trigger
in this case. However, since the protection wouldn’t trigger in real life situations, as described in
the previous paragraph, this is a moot point.
Frequency response is flat, and very extended.
The asterisk in the copy alongside the 1Hz measured lower limit is a note that it was impossible
to get a stable reading of exact level at this fre-
McINTOSH MC2102 TUBE POWER AMPLIFIER
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Square Wave Response
Frequency:1 kHz
(8 Ω//2
µF capacitive load)
Square Wave Response
Frequency:100 Hz
(8 Ω resistive load)
Square Wave Response
Frequency:1 kHz
(8 Ω resistive load)
Square Wave Response
Frequency:10 kHz
(8 Ω resistive load)
quency, so this is an approximation. The
upper limits of 55Hz (–1dB) and 123kHz
(–3dB) show this amplifier would benefit
from a wide-band source such as DVD-A
or SACD. The graphed frequency
response shows a slight (0.02dB) boost in
response below 20Hz, due to the transformer after which it’s better than 0.01dB
up to 3kHz, where it gradually rolls off to
be 0.05dB down at 10kHz, 0.1dB down at
16kHz and 0.18dB down at 20kHz. Into a
simulated loudspeaker load (the red
trace), the McIntosh’s response was not
nearly so flat, although it was still comfortably within 0.01dB from 10Hz to
15kHz and only –0.18dB at 20kHz! As you
can see, there are peaks at 60Hz and
1.8kHz of around +0.07dB and dips at
200Hz (–0.02dB) and 4.8kHz (–0.08dB).
These are nothing to get excited about,
but could conceivably have an effect on
the sound of the amplifier.
The distortion spectrum at one-watt
output was interesting more for the noise
floor at –115dB than for the distortion
products, which amount to only 2nd and
3rd harmonics. With 8-ohm loads, HDL
2
is –85dB (0.005%) and HDL3is at –95dB
(0.001%), but with 4-ohm loads, the levels
McINTOSH MC2102 TUBE POWER AMPLIFIER
creep up slightly, to –80dB (0.01%)
and –90dB (0.003%) respectively,
which would seem to indicate that
you’ll get slightly lower distortion
with 8-ohm speakers (and tap) than
with 4-ohm speakers.
Distortion increased quite dramatically at rated output, though
again the 8-ohm tap/speaker
matching gave better results than
the 4-ohm tap/speaker combination. The accompanying graph
shows harmonic distortion components out to the 17th (though
admittedly this is at –117dB). It
seems likely that the levels of second harmonic distortion at –70dB
(0.025%) and the 3rd, 4th and 5th
all at around –80dB (0.01%) would
have an effect on the sound. The
graph showing distortion into 4ohms looked to me a little like the
amplifier was clipping slightly,
rather than ‘ordinary’ distortion but
I couldn’t request a re-test because
unfortunately by the time I got to
see this graph the amplifier had
been returned to the distributor.
Channel separation was moderately good, as you can see on the
graph (and in the tabulated
results), being pretty much better
than 70dB right across the band,
with one small ‘blip’ at 1.2kHz to
–55dB. I suspect this could have
been interference break-though
from something else in the lab,
possibly a computer monitor.
Balance between the channels was
excellent, at 0.0458dB. Interchannel
phase was unmeasurably low
which would have been good for a
solid-state amplifier, but for a valve
unit, it’s truly exceptional!
Signal-to-noise ratios were excellent, though solid-state power
amplifiers are rather quieter, but noone could complain about the
weighted figures of 90dB (IHF-A)
referenced to one-watt output and
108dB (IHF-A) referred to rated output, especially since many owners
will use a passive pre-amp, or possibly connect a CD or DVD player
directly to the McIntosh, cutting out
a lot of extraneous circuitry.
The editor says he’s been copping a lot of flak because I haven’t
been including the square wave
Channels Driven Load 20Hz 2kHz 20kHz
18Ω 136 (21.3) 136 (21.3) 128 (21.0)
28Ω 127 (21.0) 121 (20.8) 127 (21.0)
14Ω 147 (21.6) 161 (22.0) Pro (N/A)
24Ω 118 (20.7) 136 (21.3) Pro (N/A)
Note: Figures in brackets are dBW—decibels referred to one watt)
Power Output Table 1 (McIntosh MC2102 Power Amplifier — 8-ohm tap)
Channels Driven Load 20Hz 2kHz 20kHz
18Ω 90 (19.5) 90 (19.5) 96 (19.8)
28Ω 84 (19.2) 89 (19.4) 89 (19.4)
14Ω 136 (21.3) 132 (21.2) 128 (21.0)
24Ω 128 (21.0) 123 (20.9) 115 (20.6)
Note: Figures in brackets are dBW—decibels referred to one watt)
Power Output Table 2 (McIntosh MC2102 Power Amplifier — 4-ohm tap)
Test Results
Freq.Resp.@ 1 watt (–1dB): 1.0Hz*– 55kHz
Freq.Resp.@ 1 watt (–3dB): 1.0Hz*– 123kHz
Channel Separation @ 1kHz: 61dB73dB
Channel Separation @ 20Hz: 68dB
Channel Balance: 0.0458dB
Interchannel Phase: 0.0 degrees
THD+N @ 1 watt: 0.010%
THD+N @ 100 watts: 0.028%
S/N Ratio (re 1 watt out): 78dB (unweighted)
S/N Ratio (re 1 watt out): 90dB (IHF A-weighted)
S/N Ratio (re rated o/pt): 97dB (unweighted)
S/N Ratio (re rated o/pt): 108dB (IHF A-weighted)
Input Sensitivity (CD input): 2.3mV (for rated output)
Input Sensitivity (CD input): 236mV (for 1 watt out)
oscillograms, so I’ve included the
set for the McIntosh MC2102 and
as you can see, they’re excellent.
Note particularly the response at
100Hz which exhibits no phase
shift whatsoever and only a tiny
tilt indicating a non-d.c. response.
Also note the 10kHz square wave’s
outstanding rise time and minimal
rounding. As you’d expect,
response into a capacitive load is
very well-controlled, with only
about a one-third overshoot. The
few cycles of ringing are damped
very quickly. The 1kHz wave is
excellent (the triangular part on the
right was the fault of the Polaroid
camera). There’s some tiny rounding, but that’s being very picky!
Steve Holding
AHF
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