INSTALLATION PRECAUTIONS
a)
Avoid locating the preamp where it will be exposed to direct sunlight, excessive humidity, dust or moisture.
Extreme environments may temporarily or permanently degrade preamp performance.
b)
Keep the preamp housing away from sources of strong magnetic field radiation, such as large video display
CRTs, large power lines or power/audio transformers in nearby equipment. Extra measures have been taken to
shield the magnetically sensitive bits inside the preamp housing. Nevertheless these measures can be
overwhelmed by strong outside influences. Keep in mind that the tiniest disturbance along with the desired
signals will be amplified many hundreds or thousands of times.
c)
Locate the preamp away from heat-radiating sources, such as other large amps, political demagogues or
space-heating equipment.
d)
Make sure the preamp and power supply is off before making any system connections. Do not remove or
insert the large 16-pin circular power supply connector when the power supply mains switch is in the on (|)
position. Do not hot plug the system.
e)
Dissipate any static electric charge build-up on your body by touching the enclosure before making or
changing any system connections. The preamp electronics are fairly robust as far as immunity to damage from
static charge is concerned, but total immunity cannot be had without unacceptable compromise of audio
performance.
f)
Be careful to feed only low-level phono cartridge signals to the preamp input connectors. Sustained line-level
signals above 15 volts peak may cause damage to sensitive MC input stages even when the preamp is in the
standby mode or when the power is off.
AC VOLTAGE SELECTION
The STEELHEAD system may be set to operate on either 117 or 234 volts A.C. by means of a rotary switch
located on the power supply P.C. board. The power supply's mains-voltage selector switch is normally preset to the
mains voltage at the customer's location prior to shipment. If, however, the preamp provenance is unknown then the
mains-voltage selector switch should be checked and reset to the correct voltage if necessary. The mains fuses must
also be checked for proper ratings and changed if necessary. Failure to correctly set the mains selector switch or use
properly rated fuses can cause extensive damage to the system which is of course not covered by the warranty.
The mains fuse may be checked by first disconnecting the IEC mains cord from the power supply’s power inlet plug.
Then gently press the small leaf spring on the side of the rectangular gray fuse retainer cap. The fuse and cap should
spring outward toward your fingers. Inspect the fuse for the proper rating; change if necessary. Refer to the fuse-rating
chart in the
specifications
section of this manual.
To inspect or adjust the mains-voltage selector switch it will be necessary to remove the top cover of the
power supply enclosure. For this you will need a #1 Philips screwdriver, and a 3/16 inch flat blade driver to change
the selector switch setting.
Before opening make sure that the power supply is unplugged from mains power and the STEELHEAD
preamp. Once inside you will see tall cylindrical high voltage energy-storage capacitors, which can be a shock
nuisance even when the supply is not energized. Therefore, if the supply has been recently power cycled, let the
supply capacitors discharge for 15 minutes prior to opening. Then remove 8 Philips 4x40 retaining screws from the
cover, followed by the cover. Locate the voltage selector switch near the mains power entry / fuse / power switch
module. The switch face is the black round object, about 1/2 inch in diameter, with white voltage numbers “110” and
“220” on the rotor and a white triangular selection indicator on the stator. Notice that the “110” and “220” markings
on the switch should not be interpreted as being the precise voltage needed to operate the preamp system. Using the 3/
16 inch screwdriver rotate the switch, if necessary, so that the mains voltage you intend to feed the power supply lines
up under the selection indicator. Be sure to replace all screws when reassembling.
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