Crown POWER-TECH 3 Instruction Manual download pdf (Page 8)

Power-Tech .1 Series Power Amplifiers

Page 8 Reference Manual

2.3 Input Sensitivity Adjustment

The input sensitivity switch inside the amplifier is set to

0.775 volts RMS at the factory.* It can be changed to

1.4 volts RMS or a voltage gain of 26 dB as follows:

1. Turn off and unplug the amplifier from the AC source.

2. Remove the input module on the back panel.

3. Locate the labeled access hole for the sensitivity switch.

4. Set the switch to the desired position.

5. Replace the input module.

When set to 26-dB gain, the Power-Tech 1.1 requires a

2.1-volt input, the Power-Tech 2.1 requires a 2.6-volt

input and the Power-Tech 3.1 requires a 3.3-volt input to

deliver full output into an 8-ohm load.

Fig. 2.4 Input Sensitivity Switch

2.4 Additional Load Protection

To protect against excessive power, a fuse can be

added in series with each loudspeaker cable. A single

fuse can protect the entire system, or one can be used for

each driver. High-frequency drivers (tweeters) are

usually more sensitive to large voltage peaks, while low-

frequency drivers (woofers) are typically most sensitive

to the heat from average (RMS) output power. To protect

your tweeters, we recommend that you use a high-speed

instrument fuse like the Littlefuse 361000 series. To

protect your woofers, we recommend using a slow-blow

fuse that more closely represents the thermal response of

your woofer. Use Figure 2.5 to find the correct value for

either type of fuse.

Example: (A) Choose the peak music power for the

loudspeaker (such as 75 watts). (B) Find the loudspeaker

impedance (8 ohms). (C) Draw a line between points A

and B. The line intersects the middle scale at the correct

fuse value (1.5 amps).

2.5 Required AC Mains

All Power-Tech

.1 Series amplifiers are shipped with an

appropriate line cord and plug. The standard cord and

Fig. 2.5 Loudspeaker Fuse Nomograph

Fig. 2.6 AC Mains Cords and Plugs

plug for each model are listed by country (or region) in

Figure 2.6. When possible, use a power receptacle on

a dedicated circuit, and always make sure it will

provide the right voltage with sufficient current. We do

not recommend operating your amplifier with voltages

greater than 10% above or below the unit’s rated

voltage. For example, if your amplifier is rated for

120 VAC, the line voltage should not exceed 132 VAC.

* Factory setting for international models is 1.4 V.

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Crown POWER-TECH 3 Instruction Manual Page 8

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