dm8
TM
TABLE OF CONTENTS
IMPORTANT SAFETY INSTRUCTIONS.............................................................2
INTRODUCTION....................................................................................................3
ELECTRONIC DESIGN.....................................................................................4
MICROPROCESSOR CONTROL.....................................................................5
INDUSTRIAL DESIGN......................................................................................6
MECHANICAL DESIGN...................................................................................7
INSTALLATION.......................................................................................................8
UNPACKING .........................................................................................................8
POSITIONING ........................................................................................................8
FRONT PANEL CONTROLS.................................................................................9
REMOTE CONTROL............................................................................................10
DISPLAY..................................................................................................................10
DISPLAY..................................................................................................................11
REAR PANEL.........................................................................................................12
CONNECTIONS.....................................................................................................13
CONNECTING TO A POWER AMPLIFIER...............................................................13
REMOTE POWER AMPLIFIER CONTROL OUTPUT................................................14
BRIDGING...........................................................................................................14
BREAK-IN PERIOD ..............................................................................................14
PROGRAMMABLE INPUT SELECTIONS................................................................14
OPERATING INSTRUCTIONS...........................................................................15
CONNECTING SIGNAL SOURCES .........................................................................15
HOME THEATRE PROCESSOR CONTROLLING VOLUME ......................................15
CONNECTING THE MAINS POWER SUPPLY CABLE ............................................15
REMOTE CONTROL BATTERIES..........................................................................15
SWITCHING THE UNIT ON ...................................................................................16
ALLOCATING SIGNAL SOURCES AND THE REMOTE CONTROL............................16
DE-ALLOCATING PROGRAM BUTTONS ..............................................................16
DISPLAYED INFORMATION.................................................................................17
DISPLAY CONTRAST ..........................................................................................17
BACK LIGHT.......................................................................................................17
VOLUME.............................................................................................................17
VOLUME – BALANCING FUNCTION....................................................................18
SWITCHING BETWEEN SOURCES.........................................................................18
PHASE CONTROL................................................................................................19
ELECTRONIC PROTECTION AND RELIABILITY.........................................19
SPECIFICATIONS & FEATURES.......................................................................20
CARE AND MAINTENANCE...............................................................................22
TROUBLESHOOTING..........................................................................................23
SERVICE..................................................................................................................24
WARRANTY...........................................................................................................25
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dm8
Important Safety Instructions
This product shall be connected to a MAINS socket outlet with a
protective earthing connection.
Only suitable approved MAINS cords, as per European
individual country requirements in the CE Low Voltage Directive
Scheme, shall be used with this unit.
Do not use extension cords: To avoid safety hazards, use only the
power cord supplied with your unit. We do not recommend that
extension cords be used with this unit.
Weighs 23 kg (50 lbs.) per unit. Shipping weight 36 kg (79 lbs)
Designed for indoor use only. The dm8 preamplifier is not
protected against liquids.
The unit shall not be exposed to dripping or splashing. No objects
filled with liquids, such as vases, shall be placed on the
apparatus.
No naked flame sources, such as lighted candles, should be
placed on the apparatus.
Designed to operate on any mains supply in the range of 90V to
240 V. 50 to 60 Hz, without any internal or external switches.
There are no user serviceable components inside this unit. Do not
attempt to open the preamplifier compartment: this may expose
you to dangerous voltages and will void the warranty.
Compartments are sealed at the factory. If the seals are broken,
the warranty will be void and all service costs will be charged to
the owner.
Requires F 1A L 250v fuse for continued protection against the
risk of fire. Never bypass or use any other type of fuse. The fuse is
located on the rear panel in the main switch.
90 - 240 V
50 - 60 Hz
10A
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
TM
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dm8
TM
Introduction
Congratulations on purchasing the HALCRO™ dm8 preamplifier.
It has taken two years and the generous contributions of leading reviewers,
distributors and dealers from around the world to design, then create, the
HALCRO™ preamplifiers. We are confident that this combination of
expertise, along with the know-how of the high-end audio industry’s leading
Research and Development team will ensure the success of the HALCRO™
preamplifiers.
The brief given to our R&D team, headed by Bruce Candy, was to produce
two models of preamplifier to satisfy the needs of every audio connoisseur:
Ÿ Lowest distortion specifications of any preamplifier in the world.
Ÿ Physical dimensions to suit a standard domestic equipment rack, while
retaining the stunning HALCRO™ industrial design signature.
Ÿ Tractable controls.
Ÿ Superior reliability.
Ÿ Innovation in design.
The HALCRO™ dm8 & dm10 preamplifiers will add no colorations to the
music. When used in conjunction with HALCRO™ power amplifier(s), all
you will hear is the original recording reproduced the way the artist intended
it to sound. No transistor or valve-added sounds are present, just a level of
musical purity that was thought impossible until now.
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dm8
TM
ELECTRONIC DESIGN
By Bruce Candy
In keeping with my philosophy of design, my basic aim was to produce a
preamplifier with which I, personally, am quite satisfied. I sincerely hope that
others will share my satisfaction with these products.
As I saw it, the major issues were:
Ÿ Zero compromise on Transparency.
Ÿ Flexibility.
Ÿ Ease of use.
Ÿ Progressive design concepts.
In order to meet this challenge, the resulting circuits have particular
characteristics:
Ÿ First, all circuits in the preamp have distortion so low that it is
immeasurable, whether THD, IM etc.
Ÿ Second, all circuits in the preamp exhibit exceptionally low noise (see
specifications).
Ÿ Third, there is no compromise whatever with the choice of components
(Vishay resistors, FKP1 capacitors etc).
Ÿ Fourth, the circuits are highly immune to electromagnetic interference.
Some inputs and outputs include both first order filters and common
mode chokes.
Ÿ Fifth, the power supply and microprocessor circuits are designed for
minimal electromagnetic emissions (extensive 2nd to 6th order filters).
Ÿ Sixth, the power supply switching frequency was chosen to be much
higher than the audio band (>200kHz).
Ÿ Seventh, the power supply rails are exceptionally well regulated,
double regulation in fact (switch-mode and linear servo loops).
Ÿ Eighth, components and design are selected for high reliability.
The volume control is implemented so as to include two identical stages in
series. This minimizes output noise.
The dm8 & dm10 preamplifiers feature balanced, unbalanced, current mode
and bridged current mode outputs. The latter consists of a non-inverted and
inverted current output. There is also an unbalanced output for tape and
headphones.
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dm8
TM
Audible relay noise
The dm8 & dm10 use mechanical relays in all switching including the volume
control because they exhibit the following ideal characteristics ;
• zero ON resistance,
• infinite OFF impedance,
• very low OFF capacitance,
• zero distortion.
In contrast, the now universally popular solid state relays/switches exhibit
none of these ideal properties and detract from performance.
Hence, sonically, HALCRO™ feels that it is worth the side effect of
mechanical clicking sounds when parameters are changed.
MICROPROCESSOR CONTROL
By Paul Rainbow
The excellent audio electronics are complemented and controlled by a number
of highly integrated micro-controllers located close to the electronics they
serve. Being as near as possible to the controlled electronics allows short
control paths and virtually eliminates internal connectors, thereby greatly
increasing system reliability.
Each amplifier channel has its own micro-controller; the front panel display
and user interface has another. A fourth micro-controller, located on the rear
connector panel, co-ordinates the activity of the others. The four microcontrollers are linked via only four interconnections each.
A unique programming feature of the microprocessor has been developed
which allows the user to dedicate a particular pair of input sockets to a
specific input device. This feature provides the user with great flexibility for
connecting input devices to the preamplifier. The rear panel has provision to
accommodate five input devices into seven physical pairs of input sockets.
There is one pair of current inputs, three pairs of balanced inputs and three
pairs of unbalanced inputs. Phono inputs do not require programming as they
are permanently allocated to the phono source (in the dm10).
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dm8
TM
INDUSTRIAL DESIGN
By Max Dickison & Tony Kearney
Product Form
The aim when designing the dm8 and dm10 was to create a preamplifier that
was unmistakably part of the HALCRO™ product family, but at the same
time a component that would compliment any high end audio system.
The preamplifier had to sit comfortably within a contemporary domestic
environment, retain the visual signature of the HALCRO™ family of
products which differentiates them from other high end audio products and
have an appearance that reflected the high level of technical innovation. As
with other HALCRO™ products, softer forms and textures are used, all
fasteners are concealed and the heatsinks are integrated into the external form
to maintain simple, clean lines.
Whilst the unique pillar forms of the power amplifiers have been carried
through to the preamp, proportions have been reworked to allow this
component to be either freestanding or housed within a standard 19” shelving
system.
Control Interface
Knobs and buttons:
The volume and input selector knobs use a unique magnetic incremental
indexing mechanism developed to provide a very subtle and reliable indexing
action. The knobs and buttons are finished in the same soft textural finish as
the pillars.
Display:
A high-resolution display was chosen in order to provide clean simple
graphics without the rough edges associated with displays of lesser quality.
The graphic layout of the display has been optimized to give prominence to
the functions that are viewed most often. These include volume levels,
balance and input selection. Functions that are accessed less often are
displayed in smaller type along the bottom of the screen. These include
stereo/mono and in-phase/out-of-phase. The volume levels for each channel
are displayed side-by-side so that when the levels are not equalized the user
will easily notice it.
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dm8
TM
Remote control:
When designing the HALCRO™ Remote Control, we aimed to reflect the
quality and forms of the HALCRO™ preamplifiers. Machined from a solid
aluminum extrusion, the remote rests comfortably in the hand with its
minimalist array of buttons falling within the natural sweep of the thumb.
Simple and logical to operate, every effort has been made to keep this product
free of unnecessary complexity.
MECHANICAL DESIGN
By Lance Hewitt
The HALCRO™ dm8 and dm10 can boast their spectacularly low noise and
distortion specifications while their cases contain inherently noisy digital
circuitry, including a switch-mode power supply, partly due to the
mechanical design of their circuit boards and the boxes that contain them.
Supports of folded aluminum serve not only as bases to which the electronics
are anchored, but also to shield different sections of the circuitry from one
another.
Each of the audio, panel and display, and power supply sections is contained
within its own internal aluminum enclosure. Cables connecting the separate
sections are few and short, minimizing both radiation and reception of
unwanted signals.
Please enjoy the HALCRO™ audio experience.
HALCRO™ has enjoyed creating perfect audio reproduction for the world's
music connoisseurs.
If you wish to contact HALCRO™ to supply feedback on your purchase or for
general enquiries, please feel free to contact us:
Email: admin@halcro.com
Telephone: +61 8 8238 0807
Facsimile: + 61 8 8238 0852
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dm8
Installation
Ensure you have read the Important Safety Instructions section on page 2 prior to
installing your HALCRO™ preamplifier. If you require assistance in the unpacking and
installation of your HALCRO™ preamplifier, please contact your dealer.
Unpacking
Undo the 4 fasteners at the base of each box. Then remove the upper part of the container
by lifting directly upwards, being careful not to rub it against the preamplifier. (To have
gained access to this manual you must have completed the above steps).
Remove the material wrapping and foam pieces, then lift the preamplifier from the base
of the container. (It is recommended that the user take off all jewelry that may scratch the
unit and put on the white cotton gloves provided with the unit.)
Remove the center piece of foam in base of transit case, to locate the remote control and
power cable.
Remove the covering from the unit. Please save it for later use.
Move the unit to its final location (see Positioning).
Important
Do not connect any cables as yet.
Safely store the packaging for future relocation of the unit and shipping if service is
required.
TM
Positioning
The HALCRO™ dm8 preamplifier can be placed anywhere indoors. There is no need to
leave room around the unit to allow it to breathe. The dm8 does not generate significant
amounts of heat.
To ensure ultimate performance and to avoid potential safety hazards, place the unit on a
firm and level surface. When placing the unit on a shelf, be certain that the shelf and
mounting hardware can support the weight of the product.
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