User manual HALCRO LOGIC DM38

[. . . ] dm38 TM Table of Contents Important Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Unpacking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] It is recommended that the unit be switched to standby when not in use. It is safer to turn the mains power off when not using the dm38. However the amplifier may be left on in the standby mode for prolonged periods. If you wish to turn the mains power off, the amplifier has a very minimal warm up period. Page 8 dm38 Electronic Protection and Reliability TM Electronic protection circuitry and amplifier reliability, alas, is an area sadly neglected by many high-end audio amplifier designers. HALCROTM has paid a great deal of attention to this area. Components Our components are selected for not only performance but reliability as well, for example: · All Halcro electrolytic capacitors are rated at a minimum of 105 degrees C instead of the usual 85 degree rating. The operational life of electrolytic capacitors is severely shortened at temperatures near the maximum temperature rating. All Halcro integrated circuits are at least "industrial grade" rather than the usual "commercial grade". Industrial grade components are rated at least from ­40 degrees C to +85 degrees C whereas commercial grade components are only rated from 0 to 70 degrees C. In addition, the electronic specifications of industrial grade components are superior to commercial grade. Electrolytic capacitor temperature rating Mean lifetime at 40 degrees Centigrade Mean lifetime at 85 degrees Centigrade Mean lifetime at 105 degrees Centigrade · 85 C (most 50, 000 Hours 2, 000 Hours (0) commonly used) 105 C (used in 180, 000 Hours 8, 000 Hours 2, 000 Hours Halcro amplifiers) Typical data from a highly respected manufacturer. Considering that most amplifiers run at significantly elevated temperatures, it can be seen from the table, that the Halcro high temperature rated capacitors are highly advantageous compared to the standard 85 degree rated devices. Page 9 dm38 Output current limiting TM In terms of maximum available output current, there are basically 3 amplifier type options: a. An amplifier with a reasonable limit placed on the maximum available output current. If indeed a 4 or 8 ohm loudspeaker does have an impedance of 1 ohm at a particular frequency, one must wonder where the heat generated is dissipated if this load is predominantly resistive or why the coupling is so poor if this load is predominantly reactive. Hence we believe that these excessively high output currents are, · · not required for well designed loudspeakers, and highly dangerous. Many people have listened to maximum available current limited amplifiers played through different loudspeakers without encountering any current limiting problems that is, obvious "cracking" sounds at very loud listening levels, except for loudspeaker or voltage overloads which are independent of current limiting. Output transistor protection Halcro uniquely incorporates circuitry which accurately calculates the mean power dissipated in the power output transistors (power FETs). Another calculating circuit then may reduce the maximum available output current according to the heatsink temperature and calculated average dissipated power in the transistors. The higher the heatsink temperature, and the higher the mean power dissipated in the output transistors, the greater this reduction. This will only occur at very high heatsink temperatures and very high mean output powers. Page 11 dm38 Unusual output conditions TM The vast majority of amplifier faults show up as high positive or negative d. c. An independent circuit in the Halcro amplifiers senses any unreasonable d. c. output voltage and switches the amplifier off if this occurs. Likewise, if any excessive output current flows for an extended length of time, this also implies a fault and an independent circuit measures this and will shut down the amplifier. Power supply output current limiting To further reduce the possibility of fault conditions causing substantial damage, the power supply is limited in its maximum available average output current. Note that this level is higher than the amplifier's normal current limiting conditions. [. . . ] This will ensure the safety of the amplifier. If you have misplaced or damaged the original packaging, you can purchase new packaging through your dealer or HALCROTM. The warranty registration form is included in this owner's manual on the following page. Please cut it out carefully along the line up the left-hand side of the page and return it to HALCROTM. [. . . ]