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Model SD135
Connect the SD135 input to the preamplifier or
electronic crossover, using only the highest grade of audio
interconnect cables. To avoid sonic degradation use the
shortest practical length of cables.
A.C. POWER CONNECTIONS: It is important that the
SD135 be connected via its supplied 20 amp IEC 12-gauge
power cord to a secure, dedicated A.C. power receptacle.
Never connect to convenience power receptacles on other
equipment. Only use the power switch on the front of the
SD135 for On/Off control of the amplifier, or the 12V start-
up trigger for remote installations.
The AC power source for the SD135 amplifier should be
capable of supplying 5 amperes for 100 or 120 volt units,
or 3 amperes for 220 or 240 volt units.
For the very best performance on domestic 100 or 120 volt
circuits, the SD135 should be connected to its own AC
power circuit branch, protected by a 15 amp breaker. The
preamplifier and other audio equipment should be
connected to a different power circuit and breaker.
The SD135 should be turned on a f t e r the other compo-
nents of your system. If the SD135 is turned on before
other components, the amplifier will amplify any extrane-
ous turn-on noises those components might generate,
which could potentially damage the loudspeakers. G o o d
operating practice dictates that the amplifier should be
turned on last, and turned off first in an audio system.
The SD135 uses a grounding system that does not require a
ground-lifter adaptor plug on the A. C. power cord to mini-
mize hum. The power cord supplied with the
SD135 has a standard grounding plug to provide maximum
safety when properly connected to a grounded wall recep-
tacle. If there is any question regarding proper grounding
procedures in your installation, seek help from a qualified
technician. Caution should be taken before using custom
after-market power cords: they must be at least
12-gauge and have a standard grounding plug properly
installed. These power cords are to be used with caution, at
the sole risk of the owner.
If electronic crossovers or other AC powered equipment is
used with the SD135 it may be necessary to use "ground
lifter" adapters on the power plugs of that equipment to
minimize system hum. Generally, the lowest hum is
achieved when the only direct connection between audio
common "ground" and true earth ground occurs in the
preamplifier, through its grounded power cord. Other
equipment in the system should have some form of isola-
tion to prevent ground loops and associated hum.
2
Single-Ended Operation
Single-ended inputs should be used with a preamplifier (or
electronic crossover, etc.) having single-ended outputs
which does n o t invert overall phase or polarity. When
using single-ended inputs, make sure the shorting jumper
pins supplied for single-ended operation are installed
on the rear panel of the amplifier between the bottom
and right socket holes of the balanced input jack,
on both channels, as shown in the accompanying rear
panel diagram.
Balanced Operation
B a l a n c ed inputs can be used with a preamplifier (or
electronic crossover, etc.) having balanced outputs. When
using the balanced inputs, remove the shorting jumper
pins before connecting balanced XLR connectors. Discon-
nenct any single-ended cables.
Always place the Power On-Off switch on the front of
the SD135 in the "Off" (left) position before connecting
the power line cord to AC power.
Installation
To insure normal component life and safe operation this
unit must be operated only in an upright position .
Adequate air flow and proper cooling can occur only if
there is no restriction above and behind the unit and on
either side. Be sure that airflow to the 12V D. C. cooling
fans located on the rear panel is not blocked.
The special non-marring elastomer feet provide adequate
spacing and stability only on a smooth, hard surface. F o r
upright stability, never operate the unit while it is sitting
on a soft surface such as a thick rug or carpet.
Due to its weight, this amplifier must be supported on a
surface specifically rated for such a load. Check with the
manufacturer of your support system to be sure it is rated
to handle this weight.
If the unit is to be operated in an enclosure such as an
equipment rack, make certain that adequate air flow above
and to each side of the unit is provided. The "ambient"
operating temperature should never exceed 120º F or 49º C.
Improper installation will cause premature component
failure and will affect your warranty, as well as the service
life of the unit.
It is normal for the SD135 power amplifier to run moder-
ately warm to the touch. All components within are operat-
ed at safe, conservative levels and will not be improperly
affected, providing the requirements outlined above are
adhered to. (Also see "Cooling Fans" section, page 3.)
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