Markbass Classic 300 - Manual (Page 9)

09
SPEAKER OUT
The Classic 300 can be connected to speaker cabinets using either 1/4” speaker cables (do not use instrument cables) or speakon speaker cables. The first high-quality Neutrik
SPEAKON COMBO jack (22) can be connected to a 4 or 8 ohm load. The second Neutrik SPEAKON COMBO jack (23) can be connected to a 2 ohm load.
WARNING: never use both jacks together! If you want to use two 8 ohm cabinets, connect one directly to the 4/8 ohm jack (22) and then link the second cabinet to the first.
The Classic 300 delivers 175W of power into an 8 ohm cabinet, 300W into a 4 ohm cabinet or 300W into a 2 ohm cabinet.
RS232 - PC
This port is used by authorized Markbass repair technicians for service and maintenance operations.
3.3.1 CLASSIC 300 MICROCONTROLLED AMP MANAGEMENT SYSTEM
The Markbass Classic 300 is a real analog tube head. But its groundbreaking Microcontrolled Amp Management System represents a major evolution in tube heads.
The microprocessor manages every parameter in the head (tube bias, tube voltage, load, fan, etc.). This keeps your sound extremely consistent every time you play the amp,
protects your amp from breakdown and malfunction, and dramatically extends the lifespan of your tubes. The powerful microprocessor also controls the 2x16 LCD screen that
shows you a cool VU meter and dual-function information screen.
Here is a short description of the main Microcontrolled Amp Management System functions:
1. POWER SUPPLY CHECK: The microcontroller performs a check of all the supply voltages and shuts down the amp when there are anomalies.
2. TUBE HEATING: In order to prolong the life of the tubes and promote tube "health", the microprocessor biases the power tubes only when they are hot enough.
The ‘Tube Heating’ delay guarantees the correct sequence of microprocessor functions.
3. BIASING: This is the main function performed by the microcontroller. Every time the head is switched on, the power tubes are accurately biased. This creates the
optimal conditions for sound quality every time you power up. The advanced biasing process also makes it possible to play with a bad tube; when a tube fails the LCD
screen gives you a warning, but lets you keep playing. The Classic 300 can operate in either LONG LIFE mode or HIGH FIDELITY mode. This can be changed at any
time, but the tubes take a moment to rebias when you switch modes. In LONG LIFE mode, the tubes use less power and less ‘tube life’ is taken out of them. HIGH
FIDELITY mode gives top quality, high-fidelity sound, but the power consumption and dissipation of the tubes increases. In either mode, unlike other tube amplifiers,
the Classic 300 is able to greatly prolong the life of its tubes by keeping them optimally biased at all times.
4. VU METER: During normal use, the LCD displays a digital VU meter.
5. LOAD CHECK: Tube amps are very delicate. But with the Classic 300, you don't have to worry! Whenever there's an input signal, the microcontroller checks the load
condition to make sure the speaker impedance is acceptable. This also protects your head from short circuiting or open circuit problems.
6. FAN CONTROL: The Microcontrolled Amp Management System monitors the internal temperature of the amp and selects from three different fan speeds, to make sure
the fan is never louder than it needs to be.
7. SERVICE MODE: On the rear panel there's a three-position switch that allows you to choose between two DISPLAY FUNCTION options. The first option (TEST 1)
shows the bias current (in milliAmperes) for the six power tubes. The second option (TEST 2) shows two different readings: on the first row you see the plate and grid
power tube voltages (in volts), and on the second row you see the cathode voltages for the driver tubes. This information is not important for daily use of the amplifier,
but is very useful for technicians.
8. RS232: This output is to be used only by authorized Markbass service technicians.