dm10 TABLE OF CONTENTS IMPORTANT SAFETY INSTRUCTIONS ................................................................2 INTRODUCTION..........................................................................................................3 ELECTRONIC DESIGN ........................................................................................................3 MICROPROCESSOR CONTROL ............................................................................................6 INDUSTRIAL DESIGN .........................................................................................................7 MECHANICAL DESIGN .......................................................................................................8 INSTALLATION............................................................................................................9 UNPACKING......................................................................................................................9 POSITIONING ....................................................................................................................9 FRONT PANEL CONTROLS ....................................................................................10 REMOTE CONTROL ..................................................................................................11 DISPLAY........................................................................................................................12 REAR PANEL................................................................................................................13 CONNECTIONS ..........................................................................................................15 CONNECTING TO A POWER AMPLIFIER ...........................................................................15 REMOTE POWER AMPLIFIER CONTROL OUTPUT ............................................................16 BRIDGING.......................................................................................................................16 BREAK-IN PERIOD ..........................................................................................................16 PROGRAMMABLE INPUT SELECTIONS ............................................................................16 OPERATING INSTRUCTIONS................................................................................17 CONNECTING SIGNAL SOURCES......................................................................................17 HOME THEATRE PROCESSOR CONTROLLING VOLUME ...................................................17 PHONO STAGE................................................................................................................17 CONNECTING THE MAINS POWER SUPPLY CABLE .........................................................18 REMOTE CONTROL BATTERIES ......................................................................................18 SWITCHING THE UNIT ON................................................................................................18 ALLOCATING SIGNAL SOURCES AND THE REMOTE CONTROL .........................................18 DE-ALLOCATING PROGRAM BUTTONS ...........................................................................19 SETTING THE LOAD RESISTANCE/CAPACITANCE FOR MOVING MAGNETIC CARTRIDGE PHONO PLAYERS..........................................................................................19 DISPLAYED INFORMATION .............................................................................................19 TM DISPLAY CONTRAST.......................................................................................................19 BACK LIGHT...................................................................................................................19 VOLUME.........................................................................................................................20 STORED VOLUMES .........................................................................................................20 VOLUME ­ BALANCING FUNCTION ................................................................................21 MONO/STEREO FUNCTION..............................................................................................21 PHASE CONTROL............................................................................................................21 SWITCHING BETWEEN SOURCES .....................................................................................22 ELECTRONIC PROTECTION AND RELIABILITY .............................................22 SPECIFICATIONS & FEATURES OF THE HALCRO DM10 .............................23 CARE AND MAINTENANCE...................................................................................25 TROUBLESHOOTING ...............................................................................................26 SERVICE ........................................................................................................................27 WARRANTY .................................................................................................................28 Page 1 of 29 dm10 TM Important Safety Instructions This unit 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 dm10 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 unit. 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. Do not attempt to open the unit as this will void the warranty and will expose you to dangerous voltages. 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. CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN 90 - 240 V 50 - 60 Hz Page 2 of 29 dm10 TM Introduction Congratulations on purchasing the HALCROTM dm10 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 HALCROTM 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: Y Lowest distortion specifications of any preamplifier in the world. Y Physical dimensions to suit a standard domestic equipment rack, while retaining the stunning Halcro industrial design signature. Y Tractable controls. Y Superior reliability. Y Innovation in design. The HALCROTM dm8 & dm10 preamplifiers will add no colorations to the music. When used in conjunction with HALCROTM power amplifiers, 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. 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: Y Zero compromise on Transparency. Y Flexibility. Y Ease of use. Y Progressive design concepts. Page 3 of 29 dm10 TM In order to meet this challenge, the resulting circuits have particular characteristics: Y First, all circuits in the preamp have distortion so low that it is immeasurable, whether THD, IM etc. Y Second, all circuits in the preamp exhibit exceptionally low noise (see specifications). Y Third, there is no compromise whatever with the choice of components (Vishay resistors, FKP1 capacitors etc). Y Fourth, the circuits are highly immune to electromagnetic interference. Some inputs and outputs include both first order filters and common mode chokes. Y Fifth, the power supply and microprocessor circuits are designed for minimal electromagnetic emissions (extensive 2nd to 6th order filters). Y Sixth, the power supply switching frequency was chosen to be much higher than the audio band (>200kHz). Y Seventh, the power supply rails are exceptionally well regulated, double regulation in fact (switch-mode and linear servo loops). Y Eighth, components and design are selected for high reliability. The figure below shows a functional block diagram of the preamplifier (Diagram 1). As can be seen, the phono stage has 4 stages. Firstly, there is an ultra low noise input stage with a gain of x 20 for moving coil cartridges. This can be switched out of the circuit train. Diagram 1 Page 4 of 29 dm10 TM The first stage is followed by a high input impedance (FET input) low noise amplifier with a gain selectable to x 4 or x 8. The output of this stage is fed to an inverting amplifier with a gain selected to be x -2 if the high input impedance amplifier stage gain is selected to be x 4, or x -1 if the high input impedance amplifier stage is selected to be x 8. (The "minus" indicates inverting.) The output of the inverting amplifier is connected back to the high input impedance amplifier stage input via a continuously variable potentiometer. A continuously variable capacitor is also connected to this input and to ground. The variable resistor and capacitor set the load impedance of the high input impedance amplifier stage and act to load moving magnet cartridges. This configuration forms an active load. The variable capacitance sets the load capacitance and the load resistance is 1/8th of the value of the potentiometer resistance. This configuration lowers the noise floor at high frequency, and its attributes are described below. The output of the high input impedance amplifier stage is, as well, fed to a 15Hz 3rd order high-pass Bessel filter. This acts as a "rumble-filter." Following this is the RIAA equalization stage. The RIAA equalization adheres to the RIAA specification within 0.25dB at all frequencies. The output of this RIAA stage is fed to a low noise input selector stage which has a gain of 2. In truth, if a phono input is selected, this gain can be set to either 1 or 2, depending upon the gain of the selected phono input. Some inputs are balanced inputs and one input is a current input with a load impedance of 51 ohms, for optimal inter-connect load matching. The equivalent input noise of the voltage inputs is approximately 3.5nV/sqrt(Hz), and that of the current input is 13pA/sqrt(Hz). 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. Page 5 of 29 dm10 TM Audible relay noise The dm8 & dm10 use mechanical relays in all switching including the volume control because they exhibit the following ideal characteristics: Y Y zero ON resistance, infinite OFF impedance, very low OFF capacitance, zero distortion. Y Y In contrast, the now universally popular solid state relays/switches exhibit none of these ideal properties and detract from performance. Hence, sonically, HALCROTM 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 microprocess ...