User manual HAFLER DH-222

[. . . ] Allow at least one inch on each side, and at least three inches to the rear for unimpeded flow. AC Line Connections and Switching NOTE: BE SURE YOUR AMPLIFIER IS WIRED FOR YOUR LOCAL LINE (MAINS) VOLTAGE BEFORE CONNECTING AC POWER! 2 The DH-222 is normally wired for use on 120 Volt 60 Hz power lines. If your line (mains) voltage is different, you will require the optional export multi-voltage transformer, which accommodates voltages from 100 to 240 VAC, at 50-60 Hz. The DH-2223 power switch may be left ON, and the amplifier switched remotely via a preamplifier or other control center, provided that device has a switched AC outlet capable of supplying 20 amperes for the amplifier, in addition to the requirements of other units being switched. Alternately, you may connectthe amplifier directly to a wall outlet, and use the front panel power switch provided on the amplifier. [. . . ] These output terminals are "floating", with the right red terminal the "-" connection, and the left red terminal the "+" connection. In this mode, THERE ARE NO CONNECTIONS TO EITHER BLACK BINDING POST OR RIGHT INPUT JACK. It is recommended to place a piece of tape over the unused connections to avoid later confusion. 4 Grounding The DH-222 employs a common ground between the two channels, which, for the input, is connected directly to chassis, and for the output, is connected to chassis through a 5 ohm thermistor to avoid ground loops. This common ground allows the use of external devices which also have common grounds, such as headphone or speaker switching boxes. Make sure that the "-", or black terminal of the amplifier is connected to the corresponding terminal of the accessory device. OPERATION Power Switch and Pilot Lamp The red bar above the power switch will glow when the power is switched on unless excessive, long term, heat sink temperature has opened a thermal breaker, or the AC line fuse has blown. If the unit has tripped off thermally, reduce the input signal to avoid high turn-on level. The red pilot bar will light a few seconds before operation is automatically restored if the DH-222 has cooled down and the power switch is left on. If a second shutdown occurs, check for inadequate ventilation, continued excessive input signal, or a severely reduced load impedance. Belayed Turn On and Protective Relay To avoid the turn-on transients generated by some preamplifiers, the DH-222 provides a 3 second delay before a relay connects the output terminals, If your preamp requires a longer delay period, consult the factory on extending the delay. The relay will also disconnect the load if significant DC is present at the output, or if the short term heat sink temperature becomes excessive, while allowing the fan to continue cooling the amplifier. 5 Initial System Check Out After initial set-up, leave the DH-222 switched off (rocker switch to the left) and turn on the rest of the system. Wait 30 seconds, and switch on the amplifier. If you hear a loud sharp "thump" from the speakers, or no sound is heard after the relay engages and signal is applied, consult the section "In Case of Difficulty" at the end of this manual. Mono / Stereo Switch This switch should be left in the STEREO position, unless bridged operation is desired, as outlined in the section "Monophonic Operation". Speaker Fuses The fuse holders on the back panel provide a measure of protection against excessive power output to the speakers. You will need the special tool provided, patience, quiet, and good hearing, but no test instruments to complete the task. Because the amplifier must be operated with the cover off, and high voltages are exposed, this should only be undertaken by a qualified technician. 7 A pair of headphones which have a high degree of isolation from outside sounds may simplify your test listening, but are not essential. If a very sensitive meter is available, it can replace the listening requirement, but your ears are better than conventional meters. Using a loudspeaker, what you hear is what (distortion) you get. PERFORMING THE ADJUSTMENTS One channel of the amplifier may be used as a driving source to provide a signal at a conventional listening level; the other is the tested amplifier. These are then interchanged to enable adjustment of both channels. Any type of signal may be used - music, white or pink noise, etc. The accuracy of the driving amplifier is not a factor - if it 1has distortion, that distortion is simply a part of the test signal, and does not detract from the test accuracy. The circuit diagram shows the appropriate connections, and the values which provide a precise attenuator to adjust the gain so that the output level will exactly match the input level. The monitor loudspeaker is connected differentrally across the outputs of the two amplrfiers. If the signals are identical, there will be no sound from the monitor loudspeaker. Any differences between the input to and output from the test amplifier represent some form of distortion, and this will be audible in the monitor speaker, either as program related content, or as noise. [. . . ] A convenient signal is the interstation noise from an FM tuner with its muting deactivated. This is similar to white, or uniform broad band noise. If no sound is heard once the relay engages and an input signal is applied, check all input and output connections, as well as the back panel speaker protection fuses. In addition to the internal 15 ampere line fuse, there are four 10 amp rail fuses, None of these internal fuses are intended to be user replaceable, and a blown condition usually indicates a need for professional service. FACTORY SERVICE & LIMITED WARRANTY If you encounter any difficulty or have any questions concerning your DH-222 amplifier, please call our Customer Service Department weekdays, 8 am to 3:30 pm Mountain Standard time, at 602-967-3565. [. . . ]