7
CONNECTING THE SPEAKERS
The power output stage is accessed via gold-plated screw block terminals, which can accept a stripped wire
up to 6 mm
2
, with either a spade mount or standard 4 mm banana plug. The use of a simple stripped wire is
not recommended due to the heavy surface oxidation to which copper wire, either nude, tinned or silver
plated, is susceptible. The output stage of GALACTRON amplifiers do not have either voltage or current
protection. For this reason, their design parameters have been greatly oversized (the heat dissipation capacity
of the final stage MOSFETs is equal to eight times the nominal value at 8 Ohms), in order to be able to
handle even a short circuit of the output terminals in the presence of a high input signal. This, however, does
not mean that shorting the output will not have any consequence. The four fuses in the power amplifier PC
board should prevent an excessive power drain by the final stages: if these fuses blow the power to the final
amplifier stage will be
cut-off and the amplifier will not function; these fuses must be replaced by a GALACTRON SERVICE
CENTER. The lack of protection and the mighty power supply allows GALACTRON amplifiers to drive any
speaker system, if the input impedance seen by the amplifier is very low (less than 2 Ohm) and the volume is
kept very high for long periods of time, the current delivered to the final amplifier stages can lead to
remarkable temperature increase.
POWER UP
GALACTRON AMPLIFIER are controlled by a microprocessor that oversees all function without, however,
in any way interfering with the audio signal. For this reason, the power up procedure differs from that of
ordinary amplifiers. When the main power switch turned to the On position, the amplifier enters Stand-By
mode. Basically, the control circuits are powered but the primary winding of the main power transformer is
not connected to the main power supply. Under these conditions, the power led will be illuminated red. To
activate the amplifier, press one of the four audio input keys on the remote control. At this point the
microprocessor will start the specific power up sequence. First, the relay that supplies the voltage to the main
power supply will be activated, and the power led turns green. After about four seconds, the output of the
preamplifier stage, which is grounded in STAND-BY mode, is enabled, and the microprocessor starts the
warm-up sequence; the warm-up led begins flashing.
WARM-UP
At this point the amplifier is ready for operation. However, due to the special “ZERO FEEDBACK” circuit
design, the amplifier is not able to express its full performance until a steady state thermal equilibrium has
been reached. Accordingly, the warm-up period, indicated by a flashing led, was adopted to identify the
period during which the amplifier should not be used if you demand the purest sound reproduction. DURING
THE WARM-UP PERIOD, IT IS NORMAL TO HEAR AN INCREASE, EVEN APPRECIABLE, OF
BECKGROUND NOISE.
Once the warm-up period has terminated, the led will be illuminated continuously. The duration of the warm-
up period is not constant. It depends on how long the unit has remained ON before being turned OFF; indeed,
the microprocessor takes into account the effective initial temperature of the heat sink.
SOURCE SELECTION
The program source is selected by pressing one of the associated keys on the remote control. With each
selection, the new source is selected in place of the previous choice. The program source selected is
visualised by an illuminated message on the front panel.
When the TAPE MONITOR key is pressed, the signal returning from the tape deck is sent to the speakers the
main source is not deselected, and its is signal continues to be sent to the tape deck. Activation of the monitor
is displayed by the associated wording on the front panel.
To de-select listening to the signal returning from the tape recorder and return to the selected source, simply
press the tape monitor key again. The wording on the front panel will disappear. If a source selection key is
pressed when the tape monitor is active, the amplifier will continue to be connected to the tape deck, but the
signal sent to the record will depend on the key pressed.
VOLUME
The volume is adjusted by using the two keys on the remote control. The volume adjustment has been
divided into steps.
The maximum attenuation before the last step is -48 dB; the last step silences the volume.
When one of the volume control keys is pressed on the remote control, a massage and an arrow appears on
the front panel, indicating if the level is increasing or decreasing. Once maximum attenuation or gain is
reached, the massage and the arrow will no longer be illuminated, indicating the limit has been reached.
Pressing MUTE key will lower the output signal by 20 dB. Activation of the mute function is indicated by a
massage on the front panel. To return to the previous volume, press the key again.
Summary of Contents for MK 2245
Page 1: ...1 Owner s Manual MK 2245 ...
