Owner`s manual

MUSIC PREAMPLIFIER SETUP AND OPERATION
Unpack the preamplifier carefully and save the packaging containers for future
shipment if required.
During operation, the MP3 gets warm. Adequate ventilation is mandatory. If the
preamplifier is to be placed in a shelf or rack mount system, allow for at
least 2 inches of open space above the unit. Make sure that the preamplifier is
at least a foot away from any power supply, to avoid hum problems.
After the preamplifier is properly positioned, make sure that the power switch
is in the OFF position. Connect the cables for the various components to be
used with the preamplifier.
For sonic performance reasons, the MP3 does not use a muting circuit! Allow the
preamplifier to warm up and stabilize before energizing your power amplifiers.
A muting circuit is not used as it would interfere with the servo loop
operation in the output section of the preamp. Its presence in the circuit
would be audible as well. Although the DC offsets generated during warmup are
low level, they could be a problem for some amplifiers and speakers.
WARNING! DO NOT TURN ON THE AMPLIFIERS IN YOUR SYSTEM UNTIL THE PREAMPLIFIER
IS WARMED UP AND STABILIZED! DAMAGE TO SPEAKERS, AMPLIFIERS OR BOTH MAY
RESULT!
Get in the habit of turning down the volume or switching to an unused input
anytime you turn your amplifier on, when you change a record, etc.
After the preamplifier is turned on, it takes about 30 seconds before it is
ready for use. During the warmup of the preamplifier, one or both of the "DC
OFFSET" LEDs on the front panel may light up. This indicates that the servo
circuit has detected a DC voltage at the output of the preamp and is
trying to correct it. If the indicator stays lit for more than a minute, a
fault is indicated and the preamplifier must be turned off immediately to
prevent damage to associated equipment. Refer to the troubleshooting page in
this manual. It is normal for the indicators to flicker at high volume
settings. The preamplifier will sound significantly better after about 45
minutes of operation.
OPERATING NOTES
Normally the preamplifier can be left on all the time, although be aware that
modern 12AT7s will last only about 3,000 hours on the outside (about 5 months).
Be sure to provide for adequate ventilation. The 12AT7 phono tubes should be
checked every 5 months if the unit is left on continuously. The unit will
sound substantially better three hours after turn-on.
The MP3 may be used with a low impedance (600 ohm) load at the input of the
power amplifier which can be used to reduce hum and buzz.
Usually you will have to adjust the GAIN TRIM for proper soundstage
(balance)effect, because the MP3 is a zero feedback design. Various tubes will
result in differing amounts of gain between left and right channels. Operate
the control SLOWLY. The GAIN TRIM controls are not in the audio path. They may