almarro A318B Quick start guide

OPERATIONAL MANUAL
A318B SET Integrated Amplifier
 almarro
3489-24 Kitagata. Iida-shi, Nagano 395-0151, Japan
Phone [phone]. Fax: [phone]. [e-mail]

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
Phone [phone]. Fax: [phone]. [email protected]
ii
Please, take the time to read through the entire manual before
operating the amplifier. At Almarro we believe that each of our
products has its own personality – it is a signature of its unique
sound. However to fully enjoy the remarkable and captivating sound
of this amplifier you have to understand the product.
This manual will help you to appreciate all features of this amplifier
and enjoy the musical sound of this product for many years to come!
Happy Listening!

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
Phone [phone]. Fax: [phone]. [email protected]
iii
Table of Contents
A Little Bit of History iv
Important Safety Instructions (Read me First!) v
Technical Summary and Features vii
Amplifier (Front View) xiv
Amplifier (Rare View) xv
Specification xvi
Installation and Operating the Amplifier xix
Maintenance Guide xxviii
Warranty xxxix

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
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iv
Thank You
For choosing the Almarro A318B Integrated
Amplifier.
You will be amazed by the performance of this
unit, hand-made in Japan with passion and
love, to high performance audio.
With Almarro, you will discover an exceptional
sound and the uncompromising quality of the
product.
Our Philosophy
We measure success by the way our equipment
sounds. We do not make any compromises
when it comes to the quality of sound.
We do not use boutique audio parts. We prefer
industrial parts from big companies readily
available and reliable. This results in products
of high quality rather than exotic parts and
overpriced material.
We do not build our amplifiers for specific
tubes- we use the right tubes for the design.
While Almarro equipment may look simple it
performs well beyond the look and price
range. This is something more and more
people are finding out about and attest to.
Each Almarro product is fully tested to ensure
that it is the best it can be.
A Little Bit of History
Tubes ruled the audio world during the Golden Age
of Hi-Fi (1937-1950). It was the time of Acrosound,
Dynaco, H.H. Scott, Fisher, McIntosh, and Thorens
to name just a few.
The Bell Labs invented transistors in 1947.
The consumer market started replacing tubes with
transistors at 1950's. By 1970 the replacement had
been almost completed (with the exception of some
guitar amps) and the Golden Age of Hi-Fi came to the
end. Building audio equipment with advanced circuit
board technology was cheaper and quicker. During the
80's, just a few boutique tube amplifiers were being
made. They were very expensive and were
manufactured in very low quantities. Solid state
however was unable to deliver better sound in spite of
many claims and better specifications than tubes.
What happened back then seemed like a miracle.
At the time when solid-state audio had become
predominantly used around the world in Japan the
tube audio not only managed to survive but also had
become part of audio culture. While the consumer
market was quickly adopting a new solid stage
technology a few very talented and ambitious Japanese
designers had started the resurrection of the tube
amplifiers. During this time Japanese engineers re-
discovered that SE (Single Ended) amplifiers can
sound beautiful and musical.
Once again the most technologically advanced nation
impressed the world by revolutionizing high-end
audio, “going back to the future” by reinventing
technology and returning to it’s original roots!

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
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v
Important Safety Instructions (Read me First!)
Read safety instructions and the entire manual prior to operating the
equipment.

The lightning flash with arrowhead within a
triangle is intended to alert users to the
presence of dangerous voltage. The voltage
may be of sufficient magnitude to constitute a
risk of electric shock.
The exclamation point within a triangle is
intended to alert users to the presence of
important instructions.
To prevent the risk of severe electrical shock makes sure that you follow the instructions. Ignoring safety
precautions can result in severe electric shock, fire or injury. Keep children and pets away from the unit. In
case of the unlikely event when the amplifier needs service have the amplifier serviced by qualified personnel
approved by Almarro Products service centers.

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
Phone [phone]. Fax: [phone]. [email protected]
vi
Important Safety Instructions
Never does any maintenance work on
the amplifier while it is operating.
Always wait at least ONE HOUR after
turning the unit off and unplug the
unit when replacing fuse or changing
tubes.
Do not install the amplifier near any
sources of heat.
Tubes become hot (The tubes used in
the amplifier heat up to a temperature of
between 250 and 350 degrees
Centigrade) and they could cause serious
burns. Never touch a tube when the unit
is on.
It takes at least 30 minutes for the tubes
to cool down after the unit is switched
off.
Keep the amplifier away from direct Sun
light.
Always use a correctly grounded power
outlet to ground the chassis of the
amplifier.
Do not modify the amplifier.
.
Never connect the amplifier to the power
source without having all the tubes installed.
In case of any smoke or burning smell
immediately turn the amplifier off.
Always connect the amplifier to the power
source category for which this amplifier is
rated. Protect the power cord from being
damaged.
Do not flip the power switch on and off
rapidly. This can damage the power supply

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
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vii
Technical Summary and Features
The A318B amplifier utilizes a one 6SL7 ( 6H9C)
tube on the input, one 6SN7 (6H8C) dual triode as
second-stage anode- follower, driving one pair of
6C33C output tubes.
Single -Ended Class A.
The Almarro A318B is an integrated single-
ended triode (SET) vacuum tube amplifier
designed as “Class A” type of amplification.
“SINGLE-ENDED" (SE) means that a single
output device handles the entire music signal.
“Class A” means that: “Grid bias and alternating
grid voltages are such that plate current in a tube
flows at all times”. (RCA Tube Manual). Most
professionals agree that “Class “A" operation is
more efficient and wastes less power as heat,
while still maintaining low distortion.
The Almarro A318B single-ended amplifier
produces the best musical effect in the critical
midrange frequencies, at a very low level
distortion.
A preamplifier is not needed when using the
Almarro A318B integrated amplifier.
In spite of the moderate power output the
A318B is a very dynamic sounding amplifier due
to its design features and combination of tubes
selected fro the design.
Tubes
Tube amplifiers are based primarily on two types
of tubes – preamplifier tubes and power tubes.
Preamplifier tubes are used to drive the power
tubes. The power tubes amplify the low-level
signal from the preamplifier into a level that is
sufficient to drive the speakers.
Input Tubes
The 6SL7 Tube
The 6SL7 (6H9C) is a dual tube is designed for
amplification of low frequency voltage. The 6SL7
(6H9C) double triode enclosed in the glass bulb
and provided with an octal base and an indirectly
heated oxide-coated cathode.
The Russian 6H9C is equivalent to the 6SL7 tube.

Operational Manual
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viii
The 6SN7 Tube
The 6SN7 (6H8C) is a dual tube designed for
amplification of low frequency voltage. The
6SN7 (6H8C) double triode enclosed in the glass
bulb and provided with an octal base and an
indirectly heated oxide-coated cathode.
The Russian 6H8C is equivalent to the 6SN7
tube.
The driver tubes are 6SN7, renowned for their
linearity and reliability. These comprise the high-
power, low restriction driver/output tube
circuitry for the A318B
The 6SN7 tube has a very open, relaxed and
graceful sound, without sacrificing details.
Introduced by RCA in 1939, this driver tube is
more rugged and sonically consistent.
Power (Output) Tubes
The most interesting aspects of the A318B are
Russian 6C33 output tubes. A version of these
rugged power triodes was applied in MIG-25
fighter aircraft.
"The 6C33C/6C33-B is a high transconductance
indirectly heated triode tube (Where
transconductance is the ratio of the current at the
output and the voltage at the input written as gm.”)
I out = Current at the output
V in = Voltage at the input
Sonically the 6C33C (6C33-B) tube produces a
well-detailed bass and has a very good dynamic
range. They offer a more traditional for tubes
“warm” sound and detailed bass with a very nice
distortion at “clipping” point - where the tube
starts to produce audible distortion at the high
power.
6C33C, 6C33C-B Tubes
The 6C33C's internal resistance is very low, which
works very well with applications which require
low voltage and high current (unlike standard
tubes which are designed as high-voltage, low-
current devices.)
Because of its sonic characteristics and low
internal resistance this tube was the best choice for
the A318B amplifier.

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
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ix
6C33C-B Tube Specification
PIN Function
1, 2, 6, 7 Heater
3 Cathode
4 Anode
5 Grid
Output Current
Output Voltage
Low
Low High
High
Low
V
High I
The graph shows the output characteristics of 6C33C.
The 6C33C has a high current capability and low internal impedance. This characteristics of the 6C33C helps to
improve bass performance.

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
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Tube Life
Tube life depends on the type of tube, and
operational conditions. A typical oxide-cathode
power tube 6SN7 (6H8C) or 6SL7 (6H9C) will last
about 2000 hours.
Output tube life is shorter as they are continually
providing significant amounts of current. Certain
specifications define the life expectancy for the
6C33C from 1000 to 2000 hours and 750-1000
hours for the 6C33C-B. In normal use, output
tubes are expected to last at least 2 years.
The sound quality of the tube is the best indicator
of tube performance.
Bias
The tube grid is a set of wires between the plate
and the cathode. This grid charge controls the flow
of electrons between a cathode and a plate when a
cathode is heated.
The negative DC voltage applied to the grid of each
output tube and controls the standing, current draw
of each tube, is called bias.
The voltage that cuts plate current to zero is called
cut-off bias.
The point where plate current no longer increases,
regardless of increases in bias voltage, is called the
saturation point.
Between cut-off and saturation, a triode behaves as a
linear device and produces minimum or no audible
signal distortions.
A typical integrated/power amplifier will provide its
best performance only when the output tubes are
biased optimally.
Any deviation from this ideal point will result in some
performance degradation, including loss of output
power and increased signal distortion. It is extremely
desirable, therefore, to have the output tubes properly
biased.
Maintaining the proper bias also contributes to
prolonging the useful service life of the output tubes.
Optimum bias provides the best balance of tube life
and sound quality
The 6C33C-B output Tubes in the A318B
amplifier require manual bias setting. (Refer to
the Bias Adjustment Procedure in this manual)
Manual bias circuits are adjusted for their proper
bias set point with the tubes fully warmed up.
The A318B amplifier employs a relay-controlled
timer to allow the tubes time to warm up and
stabilize. These circuits provide a 2-minute delay to
pre-warm the output tubes.
However during the full warm-up cycle the bias will
be set too low. This stabilization may take up to 30
minutes or even longer.
The 6C33C (6C33C-B) is an electrically unstable
tube when powered on because of the narrow gaps
between the electrodes. Therefore the 6C33C output
tubes are subject to bias drift during the first 100
hours. The manual biasing procedure will help to
overcome this tube limitation

Operational Manual
3489-24 Kitagata. Iida-shi, Nagano 395-0151. Japan
Phone [phone]. Fax: [phone]. [email protected]
xi
Plate (Anode) Follower
The A318B is a plate-follower NFB amplifier. The
6SN7 driver tube is suitable for both cathode-
follower and plate-follower circuits.
The purpose of a cathode follower design is to act
as an impedance matching device, in other words
it has very high input impedance, and a very low
output impedance.
The Plate (Anode)-follower is so called because
the anode of the amplifier tends to reproduce the
input signal in much the same manner as does the
cathode in cathode follower. As impedance-
matching devices, they are far more versatile then
cathode followers and provide good amplification
with wide frequency response and a notable lack of
distortion.
The anode follower allows for a greater gain than
the cathode follower.
The plate-follower design implemented in the
Almarro A318B improves:
Bass performance
Extends high-frequency response
Improves linearity and lowers the
distortion
4 Ohm speakers can be easily driven with
no loss of performance.
Negative Feedback (NFB)
Feedback was traditionally used to lower distortion
of an amplifier. To overcome interaction from the
loudspeaker that causes distortion and impacts the
bass due to compromised damping factor the
A318B, 6C33C SET amplifier requires negative
feedback. Also, quite often criticized, the NFB if
applied correctly, offers a powerful and detailed
sound SET amplifier is famous for.
For the purpose of obtaining low-distortion
feedback that eliminated speaker back-interactions
the A318B uses a higher 16-ohm output that
remains disconnected from the speaker load.
This makes an indirect-NFB circuit, which
minimizes the impact on sound as a result of
typical negative feedback to take an advantage of
6C33C's high current capabilities.
Transformers
The A318B uses fast-transient oversized power
transformers for better bass control and power
delivery. Normally, the power transformer of a
single-ended amplifier operates as a stable source.
In a transformer-coupled single-ended tube
amplifier, the impedance matching occurs with a
transformer. The A318B, needs power headroom
to deal with speaker back EMF. The choke coils
work for the low frequency power supply while the
power capacitors handle the high-frequency
transients. The damping factor of our A318B is
around 8 across the bandwidth. This makes for a
good combination with high-sensitivity speakers
that use under hung voice coils, which need a
strong current supply for the short and fast strokes.
Overhung voice-coil equipped speakers may need
still higher damping for their longer excursions
during dynamic peaks.
With the advent of Neodymium motors used in
many of our speakers and modern recording
conventions, damping factors above 6 or 7 are
often necessary with many of today's speakers. The
Almarro A318B transformer has output taps at 4, 8
ohms allowing it to match to a wide variety of
speakers.

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Speakers Compatibility
Most Single-Ended Class “A” amplifiers
produce the best sound when they are coupled
with efficient speakers and matched impedance
We recommend Almarro loudspeakers with an
average rated sensitivity of 89 dB/Watt/Meter
or higher and impedance 4 ohms or higher.
Greater speaker sensitivity will allow higher
listening levels before the amplifier produces
audible distortion (clipping). However because in
the A318B amplifier utilizing the 6C33C-B
tubes this eliminates needs for very high
sensitive speakers as the amplifier has more than
enough power to generate sounds of the highest
quality. The Almarro speakers rated at 4 Ohm
and 8 Ohm impedance are designed to work well
with the A318B Integrated amplifier. The
“standard” 8 and 4 Ohm loads find in most of
commercial speakers may introduce a very poor
representation of loudspeaker’s so called “real
behavior”.
It has been noticed that most of 8-Ohm
speakers have impedances as 6 or even 5 Ohms.
Therefore, while the A318B amplifier will provide
its rated power output into “standard”
measurement loads, (4 and 8 Ohms) the peak
power will occur into a 6 to 7 Ohm load (in the
case of 8 Ohm taps) and 3 Ohm load (in the case
of 4 Ohm taps).
Such optimization provides for the best possible
performance when working with “real”
loudspeakers. Therefore, we recommend
experimenting with different loud speakers to
obtain the maximum performance from each
system.
Due to the wide range of loudspeakers available,
on the market we recommend taking into
consideration the fact that simply connecting an 8
Ohm speaker to the 8 Ohm taps does not always
produce the best result..
While in some cases such a connection proved to
be optimal, other 8 Ohm loudspeakers, especially
high-efficiency models, will produce their best
sound when connected to the 6 or 4 Ohm
outputs. Similarly, we have found out that some
nominally rated 4 Ohm speakers (like Almarro
M33A) will sound best on the 8 Ohm taps.
Fig. 1
The diagram illustrates schematics of the A318B amplifier (Only Right channel is shown)

Operational Manual
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xiii
Build
The 318B amplifier is hand-made in Japan
from start to finish by experienced
professionals who adhere to critical
considerations—such as keeping signal wires
and power supply wires from running close
or parallel to each other.
We use point to point (PTP) wiring and
quality parts to increase reliability and ensure
total ease of replacement during service and
maintenance.
A point to point (PTP) wiring circuit is one
that uses no circuit boards, but makes all of
its circuit connections directly between
components, using the leads of those
components themselves and very little wire.
In the PTP amp, the signal path is usually as
short as possible—which, when done right,
can help minimize interference and noise in
the circuit—and the circuit flows logically
from input to output. The circuit itself,
therefore, tends to look very much like the
schematic diagram from which it is built.
The amplifier is finished on all sides in solid wood.
Almarro amplifiers are laid out logically with an
economical signal flow. This kind of construction
have the advantages of being easy to repair, because
almost any component can be changed by
desoldering two easily accessible joints, and lifting
out the part. They are also extremely rugged, as the
circuit board offers the components some insulation
against heat and vibration.
Each Almarro amplifier passes an extensive quality
control to ensure that it is the best it can be.

Operational Manual
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xiv
Amplifier (Front View)
Fig. 2
6C33C-B Output (Power) Tube
Power Switch
Volume Control
Input Select
6SL7 (6H9C) input tube
6C33C-B Output (Power) Tube
6SN7 (6H8C) second-stage (cathode follower) tube

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xv
Amplifier (Rare View)
Fig. 3 Output Transformer
Power supply choke Left Speaker Terminals 8 Ohm-0-4 Ohm
Output Transformer Fuse
Right Speaker Terminals 8 Ohm-0-4 Ohm Power Socket
Input RCA Connectors

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Specification
Class of Operation: A (*)
Input Connection: 3 RCA Jacks (100mV; 100ohm)
Output Connection (Speaker Binding
Posts):
4 Ohm and 8 Ohm
Output tubes 6C33C-B(6C33C) Triode mode A1 Single-End
Input tube 6SL7(6H9C) + 6SN7 (6H8C) Cathode follower
Input Sensitivity 450mV at 1kHz
Output transformers: 30w x 2
Output power: 18w/ch at 1.0V input 500Hz/8/ch
Total gain: 13.7dB (1KHz / 8ohm)
Frequency response: 20Hz - 20kHz/-6dB
Distortion: 0.75% 0.01w/10KHz)
Global Negative Feedback (NFB) Less then 5.4 dB
Hum Level (mV AC) 0.5mV at minimum volume
1.2mV at half volume
Power consumption: 240w
Dimensions: W37cm x D28cm x H20cm
Weight: 18.0 kg

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xvii
Important Recommendations for the System Setup
The standard Hi-Fi audio system consists of a few
basic components: audio source, power source,
amplifier, cables, speakers and influenced by
acoustic conditions. All components in the
system are connected together.
This link starts from the wall power outlet, then
the power cord, the source, the interconnect
cables, the amplifier and the speakers. The system
will never be able to produce better sound than
sound produced by the “weakest” component in
any part of your system. That is why it is
important to balance the entire audio system
properly to achieve a high level of sound
performance.
A good quality source (CD-Player or Turntable) is
extremely important. When choosing the Hi-Fi
audio system we strongly recommend keeping
this in mind.
For example a turntable with an MC cartridge will
be one of the suggested applications of the
A318B. This setup will explore the full musical
potential of the amplifier and release the magical
sound of the LPs.
Like any other high quality amplifier the A318B
amplifier is designed to produce superior sonic
characteristics when used in the appropriate
acoustic conditions. The acoustical conditions
of the room where your system is setup,
speaker’s location and even the location of your
listening chair - can affect sound.
For example the amplifier will sound best in
medium size rooms, having speakers located
several feet from the wall and facing your
listening chair forming an imaginary ” triangle”
with your listening chair.
We can suggest the following approximate
room dimensions as an optimal for the best
acoustic performance of the Almarro A318B
amplifier:
The width - 14 feet
The length - 16 feet
The ceiling – 7 feet
Try to avoid having any reflective surfaces like
bookshelves, furniture, and other audio-video
equipment between your speakers.
Having “clean” power is very important. We
recommend the use of an isolation transformer
or high quality power conditioner to reduce or
eliminate impact of RFI and EMI. (Radio
Frequency and Electro-Magnetic Interference.)

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Speaker’s design, type of speakers and speaker-
amplifier compatibility (impedance match) are
extremely important for achieving a high fidelity of
your system!
Speaker incompatibility can be one of the main
reasons why your system sounds poor.
Avoid using speakers with complex crossover
networks, or speakers that demand a lot of power
with the Almarro A318B amplifier.
All Almarro speakers provide an excellent
impedance match with the A318B SET amplifier.
High Quality (low impedance and high resolution)
speaker cables can make a difference. Many
professionals agree that speaker cable impedance
less than 5-8 % of the nominal speaker impedance
will work well with almost all speaker systems.
This recommendation was confirmed by double
blind tests.
The right cables for your system are not
necessarily expensive exotic cables aggressively
promoted by the boutique cables manufactures
and audio magazines.
Based on our experience we do not recommend
spending too much of your budget on exotic and
boutique speaker cables. In order for the speaker
cable to have low impedance, the conductor, cable
connectors and cable shielding should have good
quality.
We always recommend working with our
authorized dealers and determine the right
speakers for you during listening sessions (tests).

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xix
Installation and Operating the Amplifier
Installation (Step by Step)
Unpack the amplifier
Install the tubes
Placement (Select the right location)
Connect Speakers
Connecting the Source System(s)
Connecting Power Source
Operation (Turning on)
Bias Adjustment (Maintenance)
Playing Music
Break In
Procedures (Reference in the Manual)
Page xix
Page xix-xxiii
Page xiv
Page xiv
Page xiv
Page xiv
Page xiv-xxv
Page xxx-xxxiv
Page xxvi
Page xxvi
6C33C-B tube requires manual bias setting. (See the Procedure in this Manual)

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xx
Unpacking
Carefully remove the amplifier from the box. Keep
the packing material and the box, which protects
unit and tubes during shipment. It can be used in the
unlikely event that the amplifier ever requires
shipment for servicing.
Visually inspect the amplifier to ensure that there is
no damage. The tubes are shipped in a protective
packing material. The tubes are fragile. Shocks,
humidity and dust can all cause damage to them.
Treat and maintain them with great care. Carefully
unpack the tubes.
If you find damages or problem, please call Almarro
distributor and keep everything as it is. Distributor
will claim insurance and investigator may visit you.
Before shipping, the tubes are given a full
operational check and are quality tested.
We recommend using a clean dry cloth or gloves
while touching the tubes. Before installing a new
tube inspect it visually to verify that the pins are
straight and that they line up to the socket.
Carefully observe the amplifier sockets, making
sure that they are clean and there is nothing in
the socket hole.
Install the tubes
Install the driver (input) tubes 6SN7(6H8C) and
6SL7(6H9C). TThen install the output 6C33C-B
tubes as describes in the detailed steps below
(Pages xx- xxiii).