GamuT Limited Edition Di150 Solid-State Integrated Stereo Amplifier
The most transparent integrated amplifier I have ever had the pleasure of auditioning.
Review By Ron Nagle
Let us take a look back to the Enjoy
the Music.com archives. In October of 2006 our friend and colleague
Phil Gold evaluated a three-piece GamuT audio system. That Danish system was
comprised of the CD3 compact disc player, the Di150integrated amplifier and a
pair of L5 speakers. Now more than eight years have passed and we can now listen
to an evolutionary new GamuT Limited Edition version of their Di150 integrated
amplifier. At first glance, both old and new versions of the GamuT Di150
integrated amplifiers look the same. All of the advances are on the inside
incorporating a revised circuit design and higher quality internal components.
This is how the GamuT company answered my preliminary questions. "Concerning
the Limited Edition model, we have improved and refined the output stage for a
cleaner sound with even lower distortion". We are offering this Limited
Edition for the same price as the regular Di150, $11,990. Now this is
only a guess, but it sounds like they stiffened the power supply by increasing
the amount of storage capacitance. That upgrade should have been part of the
modifications. In my crazy days of modifying old Dynaco amplifiers, increasing
the power supply capacitance did improve all frequencies, but it had the
greatest audible effect near the mid bass and bass frequencies. The companies
name, GamuT, seems very odd yet it is actually derived from a Latin word. As
referenced from Websters Dictionary. I
will cite one particular attribution meaning: "A
whole series of recognized musical notes". The GamuT company
applies this as their raison d'ete. "Our
goal is not missing out on one single element among the myriads of information
that create a realistic sound".
Electron Messaging Circuits
The Danes are great designers and engineers. I don't think I
have to tell you that with such incredible brands including Gryphon Audio, which
is Enjoy the Music.com's Editor and Creative Director Steven
R. Rochlin's reference. The GamuT Limited Edition Di150 integrated amplifier,
or Di150 LE, will certainly bear that out with its clean lines and built like a
tank construction. The exterior is constructed of stainless steel and aluminum
while internally it features a heavy non-magnetic chassis for stability. About
one month after I started this project the GamuT people finally supplied me with
additional circuit information, the following is my paraphrased
The GamuT Di150LE preamplifier circuit uses a combination of
JFET and bipolar transistors. They are all identical negative types no
complementary transistors are used. The input section of the output board uses a
similar buffer configuration. The driver stage consists of NPN bipolar
transistors, capable of producing 25 watts of power, which is needed to drive
the 100 Ampere MOSFET NPN output transistors. Each transistor can handle more than 300
Amperes peak. Compared with the original GamuT Di150, the Limited Edition uses a
new output transistor and a refined driver stage, which is so stable that the
industry-standard Zobel Network (a resistor + coil in series with the speaker
output) is no longer necessary. This is claimed to yield even more control and
help produce a better soundstage. The GamuT single MOSFET principle is based
upon the use of only one output transistor per rail. Audio-grade complementary
transistors are only available with a 20 Ampere maximum rating. The advantage is
that you can avoid having 20 separate transistors on each rail trying to work
together. Even with transistors closely matched there remains differences
between them that results in phase-smearing which is clearly audible. Using one
huge MOSFET effectively eliminates the disadvantages of the traditional
multi-transistor output stage.
The MOSFET GamuT uses is an industrial grade NPN. Instead,
GamuT has implemented the NPN MOSFETs where one of them actually powers the
positive rail. This special arrangement has the added benefit that the
difference between these two identical transistors is 100 times less than it
would be in the usual complementary based output, the result of this is an
output section without crossover distortion, no emitter resistors, and an
extremely low distortion. Distortion is mainly of even-order harmonics. This
also means that the GamuT's single MOSFET design does not use what many
traditional audiophiles desire, which is Class A bias all the way to full
output. Instead, the GamuT Limited Edition Di150 integrated amplifier is a Class
AB design, yet biased to 14 watts Class A in order to run the transistors at the
best sounding temperature and to get the best sound during the first few watts
of output. GamuT's Limited Edition Di150 integrated amplifier is a true dual
mono design utilizing separate power transformers with separate secondary
windings for the pre and power amplifier circuits. The amplifiers protection
circuitry can detect DC errors, high level subsonic signals, long-term
ultrasonic signals, high temperatures and low impedance loads. And so to
summarize, the GamuT Di150LE use a dual-FET hybrid input buffer, a single Power
MOSFET for each stereo output circuit along with an extremely robust power
A Pretty Face?
The owner's manual tells us to do two things. "Please
allow the new amplifier to burn in by playing music for 100 hundred hours" and "Allow the amplifier to warm up for at least one hour before optimum
performance can be achieved". Well both of these instructions are just common
sense procedure, but both of the suggested time intervals seem unusually long.
Lucky for me the unit I received was broken in. The most eye-catching design
element is a large 2.25" diameter volume control knob. It is positioned dead
center on a 3/8" thick, 17" wide brushed aluminum front panel. The large
central volume control conceals an ALPS dual logarithmic potentiometer. The knob
overlays a rectangular dark plastic insert. Behind that dark window is a series
of blue LED's that tracks the position of the volume control. Stacked vertically
on either side of the volume control are eight function select push buttons.
There are four buttons are on the right side labeled from the top down, Bal 1,
Bal 2, CD, and Dim. The four buttons on the left side are designated Tuner,
Tape, HTH Preamp bypass and last one being for Mute. When the HTH function is
selected, you can bypass the preamplifier section and use the Di150 as a power
amplifier to drive two channels of an AV surround system. When any input is
selected, a small blue LED is illuminated next the selected button. At the top
of the rear panel are the left and right pairs of speaker binding posts. Just
below these are rows of unbalanced RCA and balanced XLR jacks. From left to
right there are two pair RCA inputs labeled TAPE OUT and OUT. Side by side two
XLR sockets they are R out and L out. Just to the right is a small toggle switch
designated HTH enable. Next in line are four pairs of RCA inputs in order they
are, HTH, Tape, Tuner, and CD. On the right rear are four XLR sockets, two are
designated Bal 2 and the last Bal 1. Not to be omitted is the fused IEC 120 Volt
My Wish List
Note: None of the following comments in any way effect the
performance of the Di150 LE Amplifier. There are a some things I believe would
benefit the Di150LE. First, GamuT should replace the inexpensive plastic remote control. There are 21
buttons on this remote control,14 of these are used for, in my case, a
nonexistent CD player. Then there are two function buttons Standby
and Phase they are present but not
used. And that leaves just 5 functioning buttons of the 21 for the integrated
amplifier. These are: Volume up, Volume Down,
Source toggle, Previous source toggle, and last a
mute function. Each of the DI150 LE amplifier's eight front panel
buttons should be included on the remote control so you could go directly to
each selection without stepping past some other functions. Finally, the rear
panel RCA connections are not commensurate with the cost of this amplifier.
These connections are actually mounted on a Printed Circuit board and sticking
through holes in the back panel. These remind me of low-fi $400 receiver versus
a $12,000 high-end audio product. It would be far better if they were individual
hardware jacks bolted to the rear panel with much more space between each one to
support high quality audio cables. When you are investing this much money in a
piece of gear, there are set minimums one should expect. A plastic remote
control with only a few buttons being usable plus the apparently low quality RCA
jacks are not the norm. Our industry is much better than this for anything
costing over $8000, generally.
It don't come easy. A reviewers task is to isolate the
performance of one review component slotted into a system comprised of totally
different components. This is exactly why it requires an intimate knowledge of a
very well-known set up we call a, Reference System. This may be characterized as
cheating but I have been playing Vinyl records with the Merrill
Audio Jens Moving Coil
amplifier reviewed in April and with a Denon DL103
moving coil cartridge feeding the GamuT Di150LE. This may not be strictly Kosher
since the Jens is on loan as a review sample. But damn, I can't help myself as
these two components love each other, and who am I to tear them asunder. The
recording was The Very Best Of Diana Krall [Verve 06025 74683 13] and it
was the most lifelike rendition yet. Getting back to my reference system, let us
try my $2500 British Creek Wyndsor phono preamplifier plugged into the GamuT.
Agai,n using the Denon DL103 cartridge feeding into the Creek loaded at 100
Ohms. Let us listen to that same Diana Krall album a second time. The track is
called The Look of Love seemed
that all the exact same musical information is present and accounted for. Maybe
I sense a small image shift. Now more of Diana's voice is to the right of
center. Also, there is noticeably more warmth to her voice. Mind you I can't say
there is anything obviously wrong, yet my $ 2500 Wyndsor phonostage just cannot
delineate the same expansive soundscape. And without that expansive sound I
don't really feel as immersed within the music. At this point I realize just how
transparent the GamuT Di150LE is to whatever characteristic is inherent in the
line sources used.
Because the Di150LE includes a HGH bypass option we can
separate the preamplifier section and use just the power amplifier to drive my
speakers. The manufacturer includes this bypass feature as an option to use the
separated amplifier in an audio/video surround system. This opens up a new path
of investigation. Let us compare my reference preamplifier to the preamplifier
built into the Di150LE. With the HTH bypass feature switched on, all of the line
level sources were rerouted to my Parasound P5 preamplifier, with the Parasound
preamplifier now up front driving the power amplifier. At this point with my own
preamplifier in the system I can determine if the power amplifier changes
anything. It takes nearly an hour of playing music for the GamuT power amplifier
to fully open up. After that hour long wait, the Di150LE very low noise floor is
so transparent that not just the soundstage but the space separating individual
players on the stage comes into focus. By a slight margin the details of that
open stage surpassed even my reference Sanders ESL muscle amplifier. Now at this
juncture with both halves of the Di150EL separated we can listen to my reference
digital source. It is a Marantz 8400 Universal CD, DVD, DVD-Audio, SACD deck
feeding Roy Hall's tube buffered up-sampling DAC25.3 DAC. Many songs and many
hours can be summarized by describing the first track from Sting's album, The Dream of The Blue Turtles [AM+CD 2750]. If
you love somebody set them free.
This track is replete with tons of studio reverb and a big driving bass tempo.
The reverberation may be artificial, but it is full of micro dynamic details
that locate and separate all of the players onto a wide and deep front
soundstage. Nothing is held back as the bass line is reproduced as a deep
driving force and the repeating tempo compels you to become involved. So now we
can directly compare the contribution of each preamplifier separately. The
Parasound is bright and quick with a tendency to sound very slightly more bright
at the treble end of things. At the same time the higher frequencies do paint
small details within the space between my speakers. However, the Di150LE
preamplifier overall has a better balanced presentation from top to bottom. The
treble does not stand out now and the midrange and mid bass are all in balanced
proportion. My Parasound preamplifier did over emphasize the higher frequencies.
Not that I found this to be objectionable as some of the warmth that should be
part of a human voice was now missing.
If we take each component's sound, the preamplifier and the
power amplifiers contribution we will find the components voice. So far each
half of the GamuT Limited Edition Di150 integrated amplifier is completely
complementary. If there are any weaknesses, they seem buried in the music. I
could not find any obvious faults. But here is where the road gets a bit bumpy
for a writer. Because when all is said and done the most outstanding
characteristic of the Di150LE is its transparency to the source. All of my
reference line sources retained all of their characteristic pluses and minuses
and the GamuT did not impose any of its own sound. I have heard the Gamut Di150 LE reproduce micro
dynamic sound that is crisp and lush, sounding with a wonderful
expansive midrange when the source contains these qualities. Yet when presented,
the Di150 LE will elicit nuance, speed, power and delicacy. It will open a wide
and crystal clear window containing subtle micro details contained within the
The ethics of performance. Can an amplifier change or even
improve on what you feed into it, or should it? The answer has to be a
resounding NO! I see the Di150LE as a bed rock starting point for building a
system from scratch. Its very natural neutrality dictates that you must proceed
carefully to match every source component. At 700 wpc it will drive even very
difficult 2 Ohm loudspeaker loads. Feed it junk and what you hear will be junk.
Appropriately, that old computer caution applies of Garbage In = Garbage Out.
GamuT's Di150LE integrated solid-state stereo amplifier is the most
transparent integrated amplifier I have ever had the pleasure of auditioning.
The promise and the possibilities are endless!
Writing this report I tried not to fall into the black hole.
It is not my intention to tell you what I feed into any component, that would be
reviewing software and some outboard processor. Rather than tell you I played a
particular CD or vinyl recording that you almost certainly do not own through a
system you do not have makes no sense to me. I have tried, instead, to isolate
and focus on the effect Di150LE amplifier has on the signal passing through it.
That to me is relevant.
Enjoy the music and remember… Semper Hi-Fi.
Review System Components
Source Components: Sota Sapphire 2 turn table and Denon 103 Cartridge, Sangean
Digital tuner, Marantz 8400 Universal CD/SACD/DVD/DVDA player. Music Hall Up sampling DAC 25.3 and headphone amplifier.
Amplification: Sanders ESL power Amplifier, Parasound Halo P5 Preamplifier.
Jens Phono Amplifier.
Speakers: Aurum Cantus Leisure 2 SE two way monitors on 24-inch stands,
Mark Daniels Omni Harmonizer tweeters, Onyx Rocket Strata Mini 3.5 way
Cables: Kimber Kable 12tc 11ft. Kimber Kable 8TC Jumpers,
Nordost Red Dawn, Chord Silver Siren, Homemade Teflon and Autobahn
AC Power: Wire World 10 gauge IEC line cord, Power Cords: Kaplan Cables
12 gauge IEC
Power Conditioning: Islatrol Industrial 20
Ampere AC line conditioner, Richard Gray
20 Ampere Sub Station. Alpha Core Balanced Transformer Power Supply, Audio Power PE-1
power enhancer, Triad 2 Ampere isolation transformer.
And a comfortable chair with a 12' X 19' room.