Crown Audio STUDIO AMPLIFIER Filter Cleaning, Switch to the left to isolate or lift the grounds

Studio Reference I & II Professional Studio Amplifiers

METER ON/OFF SWITCH

OFF

®

ON

OUTPUT LEVEL DYNAMIC RANGE

METER MODE SWITCH

Fig. 4.4 Meter Switches

The input sensitivity switch is located inside the amplifier’s P.I.P. compartment. It is factory-set to a fixed voltage gain of 26 dB. For standard 1 kHz power into 8 ohms, this is equivalent to an input sensitivity of

4.0volts for the Studio Reference I and 2.7 volts for the Studio Reference II. If needed, it can be switched to a sensitivity of 0.775 or 1.4 volts. Here is the procedure:

1.Turn off the amplifier and disconnect the power cord from the receptacle.

2.Remove the P.I.P. module.

3.Locate the access hole for the sensitivity switch inside the chassis opening (see Figure 4.5).

4.Set the switch to the desired position noted on the access hole label.

5.Replace the P.I.P. module and restore power.

The ground lift switch located on the back panel can provide isolation between the phone jack input grounds and the AC (chassis) ground. It does not af- fect the P.I.P. module’s input connectors. Slide the

SENSITIVITY SWITCH INSIDE ACCESS HOLE

1.4 V

26 dB

0.775 V

This amplifier is equipped with a selectable input sensitivity. Remove the P.I.P. module to access the sensitivity switch.

BALANCED	CH-2		CH-1	UNBALANCED
INPUT WIRING				INPUT WIRING
+ TIP				+ TIP
– RING		INPUT GROUND LIFT
GND SLEEVE		LIFT	(MONO)	GND SLEEVE

(AFFECTS PHONE INPUTS ONLY.)

GROUND LIFT SWITCH

Fig. 4.5 Input Sensitivity and Ground Lift Switches

switch to the left to isolate or “lift” the grounds.

Note: The noninverted and inverted signal lines for the P.I.P. module are connected in parallel with the corre- sponding lines of the phone jack inputs. The input sig- nal grounds are not paralleled. Specifically, XLR pins 2 and 3 are connected in parallel with the tip and ring of the corresponding phone jack. However, pin 1 of the XLR is not connected in parallel with the sleeve of the phone jack. This makes it possible for a P.I.P. module to handle its own signal grounds independently.

The amplifier’s circuit breaker protects the power sup- plies from overload. The breaker’s reset switch is lo- cated on the back panel. Facing the back panel, move the reset switch the left to disconnect power to the power supplies, or to the right to reconnect power. If the circuit breaker trips, the front panel enable indica- tor will turn off. If this occurs, turn off the enable switch, flip the reset switch to the right (on), and then turn the enable switch back on. If it trips again or the amplifier does not operate properly, contact an authorized ser- vice center or Crown’s Technical Support Group.

4.5 Filter Cleaning

A dust filter is provided on the amplifier’s air intake (see Figure 2.1). If this filter becomes clogged, the unit will not cool as efficiently as it should and high heat sink temperatures may produce lower-than-normal output.

To clean the filter, gently pull it away from the front panel and wash it with mild dishwashing detergent and warm water. Be sure the filter is dry before you reinstall it. Replacement filters may be ordered from the factory.

Dust filters are not 100% efficient—long term this may require heat sink cleaning by a qualified technician. In- ternal cleaning information is available from our Tech- nical Support Group.

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