Hafler DH-200, Руководство по сборке и эксплуатации

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INSTALLATION
The DH-200 is most likely to be ihstalled out of sight in
most applications, since its power may be controlled by the
AC switching of most audio preamplifiers, like the Hafler
DH-101. If your control unit does not provide switching
capacity sufficient for the amplifier's 5 amp needs (plus other
equipment it is also switching), you should use the amplifier's
own power switch. In that case, turn on the preamplifier first;
then turn the amplifier on a few seconds after the preamp has
been turned on, to avoid any unnecessary turn-on transients
from some preamplifiers. Likewise, switch the power
amplifier off first.
If the amplifier is to be installed close to a record player,
you should first check its position for freedom from hum
pickup by the cartridge from the field radiated by the power
transformer of the DH-200. Although the design of the
transformer minimizes such radiation, certain cartridges are
more sensitive than others, and require separation from the
amplifier. Check at a comparatively high volume setting, and
while swinging the tone arm throughout its arc. Often a few
inches additional spacing will eliminate the problem.
Be sure to provide sufficient ventilation for the amplifier.
Unobstructed air circulation around the finned heat sinks
and above the amplifier is important for long, trouble-free
life. Never put anything on top of the cover perforations. It is
normal for the top and the heat sinks to become warm in use.
It is expected that the amplifier will always be resting on
its feet, which should be on a hard enough surface that air
flow underneath is not obstructed. If it is mounted in a rack,
or through a panel, the feet may be removed so long as ade­
quate ventilation is provided through the bottom openings.
OPERATION
The red pilot lamp which is integral with the power
switch glows whenever the amplifier is turned on. A blown
AC line fuse is the most likely cause if it is not illuminated
when the amplifier is switched on.
The yellow lens is a high temperature indicator. While it
is not likely that you will ever see it lighted, if it is, the
amplifier will not produce sound. It indicates that one of the
thermal breakers has shut down the amplifier because of ex­
cessive temperature rise in a heat sink. When the heat has dis­
sipated in a few minutes, the amplifier should return to nor­
mal operation. If the lamp again lights, check for insufficient
ventilation, or an excessive input signal, or an input which
may have dangerous signal content (such as oscillation).
Failing evidence of this, the amplifier may have malfunc­
tioned. Because of the very large heat sinks, it is highly
unlikely that any normal signal will cause the amplifier to
overheat.
Loudspeaker Fuse Selection
The DH-200 power amplifier is supplied with 2 amp
fuses in the speaker lines. Experience has shown that since an
overload must exist for a few seconds for a fuse to blow, a 2
amp fuse will protect most speaker systems, and only blow
when overload occurs. Smaller fuses tend to blow too easily,
and larger fuses do not adequately protect most speaker
systems.
A pair of 5 amp fuses are also supplied as alternatives for
the speaker fuse holders. These should be substituted if the
power output of the amplifier is to be tested, or if the
amplifier is to be operated at very high power levels into 4
ohm loads.
If the manufacturer of your speakers recommends a
specific value of fuse for their protection, we suggest that you
obtain 3AG fuses of that value and substitute them for the
ones supplied.
Loudspeaker Power Ratings
There are no U.S. standards for rating the power han­
dling capabilities of loudspeakers. As a result the manufac­
turers' usual "music power" ratings, or suggested amplifier
limits, are of only minimal help in determining safe operating
levels with amplifiers which can deliver substantial amounts
of power. You must take into consideration the type of
music, and the levels you like, to provide long term trouble-
free operation of your speaker choice, when you have a size­
able amplifier like the DH-200.
Connections
A C
The A C power cord should be plugged into 120 volts, 60
Hz, on the switched output of a preamplifier which can pro­
vide at least 5 amps, or 600 watts. Then the amplifier power
switch may be left on, and it will be controlled by the rest of
the system. Or, it may be plugged into a 120 volt wall outlet,
and switched on and off independently.
If your line voltage is different, be sure you have the
alternate power transformer which can accommodate several
line voltages, and be sure it is wired for your mains voltage as
described later in this manual before you plug in the
amplifier.
Input
Conventional shielded cables, such as those supplied
with your preamplifier, provide the input signal to the
sockets on the back panel of the DH-200. Be sure that the
outer shield connection is secure, to avoid hum. The length
of these cables (so as to permit remote location of the
amplifier, if desired) is limited only by the output impedance
of the preamplifier. If it is 1,000 ohms or less, as with the
DH-101, for instance, cable lengths up to 100 feet are per­
missible without loss of performance. Special low .maci-
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