Galactron MK 2250, Owner'S Manual, Page: 6 / 10

6
HOW TO OPERATE THE AMPLIFIER
CONNECTING SPEAKERS
The power outputs are made with screw terminals gold, able to accept both bare wire up to 6 mm2, both
terminations fork, both terminations standard banana with 4 mm diameter. the use of simple stripped cable is,
however, not recommended due to the strong surface oxidation of copper, both naked tinned or silvered. The
amplifiers Galactron have no protection whatsoever on the outputs, either in voltage or current. For this
reason the output stages have been made with a huge over sizing (the dissipation capacity of the mosfet end
is equal to eight times the nominal power of 8 Ohm), so as to withstand without damage the short circuit of
the output terminals, even in the presence of strong input signals. This does not mean, however, that any
output short circuit does not have any consequences. Inside there are 4 fuses on the amplifier power supplies
that prevent final drawing too much power: to burn them to the finals due to a power outage and then the
amplifier stops operating. To replace them you need to bring the amplifier at a service Galactron center.
The lack of protection and robustness Galactron supply allows the amplifiers to drive any speaker, as is its
low input impedance, without the risk of saturation and dynamic compression. In case the impedance seen by
the amplifier is particularly low (less than 2 ohms) and the volume is kept very high for long periods, the
current delivered by the final cause a considerable increase of the temperature of the heat sink.
POWER
Galactron The amplifiers are controlled by a microprocessor that controls all functions, even without
intervening in any way the audio signal path. For this reason, the ignition procedure differs from that of
normal amplifiers. Bringing in the "ON" the power switch the amplifier goes into standby mode: in practice
are fed the control circuits, but it is not connected to the network the primary winding of the power
transformer primary. In this situation, the LED "POWER" lights red.
To turn the amplifier simply press the Power button on the front panel to the right, at this point, the
microprocessor starts the ignition process itself. First, the relay that supplies power to the power supply main,
and the LED "POWER" After about 4 "output of the preamp stage, that the unit is in stand-by mode is
shorted to ground, is enabled, the microprocessor initiate procedures to control the heating and the red led
with the selected source flashes.
HEATING
At this point, the amplifier is ready to operate. However, because of the particular circuit structure, devoid of
total feedback loop, the amplifier is not able to express all its qualities until it has been reached a certain
thermal stability.
During heating, it is normal to an increase, even significant, of the background noise.
The duration of the heating period is not fixed, but depends on the time in which the device has been stopped
and how long it has been on before switching off: in fact, the microprocessor takes into account the effective
initial temperature of the heat sink.
SOURCE SELECTION
The source selection is made by pressing the buttons on the remote control or by turning the knob on the
front panel. For each selection the new source is switched in place of the previous year. The selected source
is displayed when the relative written on the front panel.
Switching the source, the knob will lower the volume automatically, and then bring it back to a pressure at
about eight o'clock, which you can then raise or lower the volume to your liking.
VOLUME
The volume control is done using the two buttons on the remote control or by turning the knob in the center,
on the front panel. The adjustment of the volume has been divided into forty-eight steps, very close together
when there is little attenuation, and progressively increasing hand in hand that the signal is attenuated.
The maximum attenuation possible before the last shot is -48 dB; taking the last shot because the total
silencing.