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 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 six input devices into nine physical pairs of input sockets. There are two pairs of dedicated phono inputs, 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. Page 6 of 29 dm10 TM INDUSTRIAL DESIGN By Max Dickison & Tony Kearney Product Form The aim when designing the dm8 & dm10 was to create a preamplifier that was unmistakably part of the HALCROTM 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 HALCROTM 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 HALCROTM 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 or 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. Page 7 of 29 dm10 TM Remote control: When designing the HALCROTM Remote Control, we aimed to reflect the quality and forms of the HALCROTM preamplifiers. Machined from a solid aluminum extrusion, the remote rests comfortably in the right 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 HALCROTM dm8 & 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 HALCROTM audio experience. HALCROTM has enjoyed creating perfect audio reproduction for the world's music connoisseurs. If you wish to contact HALCROTM 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. Page 8 of 29 dm10 Installation Ensure you have read the Important Safety Instructions section on page 2 prior to installing your HALCROTM preamplifier. If you require assistance in the unpacking and installation of your HALCROTM 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. Positioning The HALCROTM dm10 preamplifier can be placed anywhere indoors. There is no need to leave room around the unit to allow it to breathe. The dm10 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. TM Page 9 of 29 dm10 Front Panel Controls TM Figure 1 1. Headphone Jack 2. Remote Sensor Window 3. LCD Information Display 4. 5. 6. 7. 8. Balance Control Left Standby/On button Mute button Balance Control Right Input Select Control 9. Volume Control 10. Phase button 11. Mono/Stereo button 1. Headphone Jack: This jack may be used to listen to the dm10's output through a pair of headphones. Ensure that the headphones have a standard ¼" stereo plug. 2. Remote Sensor Window: Behind this window is a sensor that receives infrared signals from the remote control. Aim the remote at this area and do not block or cover the sensor window. 3. LCD information display: This display delivers messages and system status to assist you in operating the unit. See page 12 for a complete breakdown on the display. 4. Balance Control Left: Using this button in conjunction with Balance Control Right (Fig 1, 7), the user can change the relative volume for the left and right channels. Pressing the Left button will increase the volume on the left hand channel and decrease the volume on the right. 5. Standby/On button: The Halcro dm10 is designed to remain in standby mode when not in use. This button will toggle the unit between Standby and On. To turn the unit off completely, use the Main Power Switch on the rear panel. 6. Mute button: Depressing this button will Mute the output to the speakers but not the headphones. Page 10 of 29 dm10 7. Balance Control Right: Using this button in conjunction with Balance Control Left (Fig 1, 4), the user can change the relative volume for the left and right channels. Pressing the Right button will increase the volume on the right hand channel and decrease the volume on the left. 8. Input select control: By turning this knob, the preamplifier will scroll through all programmed input devices (CD player, Tuner, DVD, etc.) attached to the unit. The corresponding selected input is displayed. 9 Volume control: Turn this knob clockwise to increase the volume and counter-clockwise to decrease the volume. 10. Phase button: Depressing this button will toggle the unit between in-phase and out-of-phase mode. 11. Mono/Stereo button: Whenever Phono is selected, depressing this button will change the unit between Stereo and Mono modes. TM Remote Control 1. Volume buttons 2. Mute button 3. Standby/On button 1. Volume buttons: For volume control and also used in conjunction with the function button for various function selections. 2. Mute button: Press to Mute sound to the loudspeakers, press again to reactivate the sound. 3. Standby/On button: Press to switch the system between Standby and On. Figure 7 Note: Remote control takes 3 x AAA batteries (supplied) 4. Signal Source buttons 5. Function button 4. Signal Source buttons: Press to select any one of 6 signal sources on the dm10. 5. Function button: Press to choose the following functions: balance between the speakers, in-phase and out-of-phase and stereo/ mono. See relevant operating instructions for full details Page 11 of 29 dm10 Display Figure 2 Figure 3 TM Figure 4 Figure 5 1. Main Information Display 2. Signal Source Indicators 3. Signal Source Location Indicator 1. Main Information Display: The information provided on this display changes depending on what function is currently being processed. In normal use it will display the volume of both the left and right of the system (fig 5). When a different signal source is selected it will appear on the main display for a few seconds. (fig 3, fig 4). 4. Phase Indicator 5. Stereo Indicator 2. Signal Source Indicator: Displays the signal source which is currently selected. 3. Signal Source Location Indicator: Displays which input the signal source has been connected to. 4. Phase Indicator: Displays whether the unit is in- or out-of-phase. 5. Stereo Indicator: Displays whether the unit is in stereo or mono mode. Page 12 of 29 dm10 Rear Panel TM Figure 6 1. Phono Capacitance selector 2. Phono Resistance selector 3. Phono Ground Terminal 4. Phono Gain Switch 5. Phono Cartridge selector switch 6. 7. 8. 9. 10. 11. 12. Phono Stage inputs Programmable inputs Program buttons Tape Monitor Output Output sockets Ground switch Remote sensor window 13. Main power switch, mains socket and fuse holder 14. Remote Power Amplifier Control output 15. Output selector switch 1 & 2 Phono Resistance & Capacitance selector: Allows the user to precisely match the dm10 to the capacitance and resistance of the phono cartridge. 3. Phono Ground Terminal: Will ensure your phono unit is grounded when using unbalanced inputs. 4. Phono Gain Switch: Allows the user to set the phono input x1, x2 or x4 to match the output of the cartridge. 5. Phono Cartridge selector switch: Allows the user to choose between a moving magnet or moving coil cartridge. 6. Phono Stage inputs: Allows the user to connect the turntable to either the Balanced or Unbalanced inputs. Page 13 of 29 dm10 7. Programmable inputs: Provides connection to your signal sources. It does not matter which input each source is connected to, as these inputs are allocated using remote control. 8. Program buttons: Allows the inputs to be programmed by the remote control. They will remain illuminated once they have been allocated ­ see Connecting signal sources and Allocating signal sources and the remote control on page 17/19 9. Tape Monitor Output: For recording direct to tape. 10. Output sockets: Used to connect the Pre Amplifier to Power amplifier(s). 11. Ground switch: If the dm10 is attached to a power amplifier leave this switch on Remote. If the unit is not attached to a power amplifier and the user is using the headphones, switch to Local. TM 12. Remote sensor window: Remote sensor for programming purposes. Point the remote at this window when programming the dm10. 13. Main power switch, socket and fuse holder: Once the dm10 has been programmed, the main power switch can be left on and the dm10 left in standby when not in use. If the main power switch is turned off, all programming is stored in memory. 14. Remote Power Amplifier Control output: Connect a cable from this output to the power amplifier(s) and the dm10 will switch the power amplifier(s) between Standby and On. 15. Output selector switch: Allows the user to select the type of output required, Balanced, Unbalanced or Current. see Comments on the different dm10 Outputs on page 15. Page 14 of 29 dm10 Connections Connecting to a power amplifier TM Each dm10 has: 2 pairs of unbalanced current outputs (use 1 pair for un-bridged power amplifiers, use both for driving bridged amplifiers), 2 pairs of unbalanced voltage outputs and 2 pairs of balanced voltage outputs for power amplifiers. Select the method you wish to run your power amplifiers in, and connect the units using high quality cables. Outputs are color coded: Positive +, Right channel (Red Bezel). Negative -, Left channel (White Bezel). The dm10 will control power amplifiers from balanced and unbalanced voltage sources, as well as an unbalanced current source. The dm10 will also control power amplifiers in bridged pair configuration. Custom made cables are required to run bridged power amplifiers from the balanced Voltage Output (Fig 8). Figure 8 Comments on the different dm10 Outputs The balanced voltage outputs or current-mode outputs are most desirable for minimizing earth loop generated mains hum and ripple, or high frequency interference if they are a problem. Earth loop generated mains hum and ripple, or high frequency interference should not be a problem unless the source equipment is poorly designed. Power Amplifiers with current-mode inputs are rare and are most likely to have an RCA input socket. The advantages of this are: Y Y Earth loop generated mains hum and ripple are minimized Cable, plug and socket-generated interference are minimized (from poor connections which may be affected by sound vibration for example). The unbalanced voltage output is quite satisfactory so long as earth loop generated mains hum and ripple are not a problem. Page 15 of 29 dm10 Remote Power Amplifier control Output TM The dm10 has a remote power amplifier control output (fig 6,15) which will remotely switch the HALCROTM amplifiers from Standby to On. Cables can be purchased through HALCROTM for details please email us at: service@halcro.com . Bridging The dm10 will control bridged power amplifiers. A bridging kit can be purchased through HALCROTM for details please email us at: service@halcro.com . Break-in period The dm10 does not require a break-in period. The electronic break-in period is completed at the factory. Programmable Input Selections The dm10 has seven available pairs of programmable input connectors, three unbalanced, three balanced voltage inputs and one unbalanced current input. The Phono input is pre-allocated to the phono 'source' and can not be changed Input Modes Unbalanced current input Balanced voltage input Unbalanced voltage input Required output source impedance RCA: Infinite source impedance XLR: Low source impedance RCA: Low source impedance Input impedance 50ohm input impedance 10kohm + 10kohm input impedance 10kohm input impedance Page 16 of 29 dm10 Operating Instructions Connecting signal sources TM As a safety precaution please ensure that the unit is not connected to the mains power while connecting signal sources. When you initially receive your preamplifier all the inputs are de-allocated. If you are changing your signal source units, de-allocate the input source first ­ see Deallocating Program buttons on page 18 Connect all signal source units (e.g. CD player) to the terminals (Fig 6, 7) at the rear of the preamplifier, make note of which input each signal source unit is connected to. Home Theatre Processor controlling volume As a safety precaution please ensure that the unit is not connected to the mains power while connecting a Home Theatre Processor. Connect your Home Theatre Processor to any of the programmable inputs at the rear of the preamplifier. Program the preamplifier to the unit using Allocating signal sources and the remote control on page 19. We recommend you use the DVD function. To set the preamplifier to operate with zero gain, adjust both volume channels to 0.0db. The preamplifier will then have no effect on the volume. You will now be able to control the volume of your system by using your Home Theatre Processor volume control. Phono Stage Connect your turntable to the appropriate input connectors (Fig 6, 6) located on the left of the rear panel. The dm10 has the option of connecting turntables with either balanced or unbalanced outputs (only one turntable should be connected at once). When using unbalanced inputs ensure that the turn table is grounded through the preamplifier's Ground Terminal (Fig 6, 3). Select either the moving magnet or moving coil cartridge, (Fig 6, 5) to match your turntable. The dm10 has three gain settings for the phono input: x1, x2 and x4 (Fig 6, 4).. This allows the user to match the preamplifier to the output of the cartridge. Select appropriate gain level The dm10 can be precisely matched to the capacitance and resistance of the moving magnet cartridge by adjusting the corresponding knobs at the rear of the unit (Fig 6, 1&2). The phono button on the remote control is permanently allocated. Page 17 of 29 dm10 Connecting the Mains Power Supply Cable TM Plug the main power cable into the dm10's main power socket on the rear of the unit. (Fig 6, 13). Remote Control Batteries Remove the battery cover from the rear of the unit, insert the three supplied AAA batteries into the unit (ensure that the polarity is correct). Refit the battery cover. If the remote control will not be used for a period longer than 1 month remove the batteries. Switching the unit on Switch the main power switch to On. When the unit is switched on at the main power switch (Fig 6, 13) the pre- amplifier will go into Standby mode. Switch the unit on by pressing the Standby/On button on the unit or the remote control. To return the unit to Standby mode press the Standby/On button again. Note: To continue the set up process, the unit must be On, not in Standby. Allocating signal sources and the remote control All inputs must be allocated using the remote control (Fig 7). permanently allocated to the Phono inputs. Note: The Phono selection is Once the signal source units (e.g. CD player) have been connected to the input connector terminals (Fig 6, 7) at the rear of the preamplifier, ensure that the preamplifier is On, not in Standby mode. Depress the applicable program button (situated above the connectors) and simultaneously point the remote control to a remote sensor window and press the button on the remote control which best describes the signal source unit you have connected. The program button will flash twice and will remain illuminated, indicating that this pair of input connectors are now allocated to the selected signal source unit. Repeat this process for all signal source units (maximum 5 plus Phono). If the device label that is being depressed on the remote control has been previously allocated to another connector pair, this pair will now be de-allocated. Page 18 of 29 dm10 De-allocating Program buttons TM Note: Ensure the location being de-allocated is not the currently selected input, the currently selected input can not be de-allocated. Press and hold the applicable program button and simultaneously point the remote control to a remote sensor window and press the Mute button. The Program Button will flash twice and then remain off. This input has now been de-allocated and can be used for another signal source unit. Setting the Load Resistance/Capacitance for moving magnetic cartridge phono players There are three ways of setting the continuously variable knobs (fig 6, 1&2) 1. According to the manufacturer's recommendations. The actual load capacitance of the cartridge should be set to the value recommended, minus the capacitance of the interconnect between the phono-stage and preamp. 2. By using test instruments. This requires an oscilloscope and a test record which includes tones at several different frequencies between 10 and 20kHz or a swept frequency which includes 20kHz. The oscilloscope should be plugged into the preamp tape output and the level noted for different frequencies above 10kHz. Knobs should be empirically set for flattest frequency response. 3. Empirically by ear, so long as you can hear up to 20kHz! Displayed information In normal use the center of the display will display the volume of both the left and right of the system. When a different signal source is selected, it will appear in the center of the display for a few seconds (fig3, fig4). Display Contrast To adjust the display contrast, press and hold any of the Program Buttons on the rear panel (fig 6, 8) and turn the Volume control on the front panel until the desired contrast is achieved. Back Light The backlight can be turned on and off by using the remote control. Press the function button once (fig 7, 5) then the Mute button (fig 7, 2) to toggle the back light on and off. Page 19 of 29 dm10 Volume TM Front Panel To change the overall volume of the unit, use the Volume Control Knob (Fig 1, 9). Turn knob clockwise to increase the volume (the maximum volume is +20db) and counter-clockwise to decrease the volume (the minimum volume is -60db). To mute the system, continue to turn the knob counter-clockwise until the word MUTE appears on the display, or press the Mute switch (Fig 1, 6). Remote Control To change the overall volume of the unit, use the Volume buttons on the remote control (Fig 2,1). To Mute the loudspeakers, press the Mute button (Fig 2,2). To un-mute the loudspeakers press the Mute button again. Mute When the Mute button is pressed, the output to the power amplifier is disabled, the db symbol on the display is replaced by a symbol that looks like a speaker with a line through it and the headphone volumes are used and displayed. If the Mute button is pressed again the preamplifier output to the power amplifiers is enabled, the power amplifier volumes are used, displayed and the dB symbol returns. Stored Volumes The dm10 memorises two volume levels. These setting are for the Headphone output and the Power Amplifier output. A volume setting for each programmed input source is memorised on either power off or on selection of a different input. On re-selection of the input, or on power up, the previously memorised volume is returned. This accommodates differing source outputs. For example, a modern CD player may have an output up to a few volts, whereas an older type of analogue tape recorder may only output a few hundred millivolts. This feature will return the volume setting to the previous value. After power up and switching from Standby to On the preamp will enter the mode it was last in when the power was turned off. NOTE: If the mode is such that the preamplifier output is directed to the amplifiers outputs, power amplifier set of volumes are used and displayed. By plugging in the headphones music will be heard through both the headphones and the amplifier outputs (adjusting volume on the preamplifier will not effect the stored headphone setting, but it will effect volume you hear through the headphones). the the the the Page 20 of 29