Crown Audio STUDIO AMPLIFIER AC Mains Power, Available from most electrical supply stores

available from most electrical supply stores.

3.3.6 Additional Load Protection

Studio Reference amplifiers can deliver very high power levels, so it’s a good idea to add protection for your loudspeakers if it is not built-in. Loudspeakers are subject to thermal damage from sustained overpower- ing and mechanical damage from large transient volt- ages. In both cases, fuses may be used to protect your loudspeakers, or you may opt for the convenience of a P.I.P. module that provides similar protection.

Thermal protection and voltage protection require dif- ferent types of fuses. Slow-blow fuses are used to pre- vent thermal damage because they respond to thermal conditions like a loudspeaker. High-speed instrument fuses like the Littlefuse 361000 series are used to pro- tect loudspeakers from transient voltages. The nomo- graph in Figure 3.16 can be used to select the correct fuse for thermal or voltage protection.

There are two common ways to install the fuses. One approach is to put a single fuse in series with each out- put. This is easy because there is only one fuse per channel to install. But if the fuse blows, power is re- moved to all of the connected loads.

Studio Reference I & II Professional Studio Amplifiers

A better approach is to fuse each driver independently. This allows you to apply the most appropriate protec- tion for the type of driver being used. In general, low- frequency drivers (woofers) are most susceptible to thermal damage and high-frequency drivers (tweeters) are usually damaged by large transient voltages. This means that your loudspeakers will tend to have better protection when the woofers are protected by slow- blow fuses and high-frequency drivers are protected by high-speed instrument fuses.

Depending on the application, you may want to use a specialized P.I.P. module to protect your loudspeak- ers. Again, some modules are more appropriate for long-term thermal protection, while others are more ap- propriate for protection against transients. A Smart Amp™ IQ-P.I.P. module is most commonly used for long-term loudspeaker thermal protection. Each Smart Amp channel provides an independent “smooth output limiter” that controls average output levels over time while it allows transients to pass.

Most of the other P.I.P. modules that provide signal- driven compression can be used to prevent loud- speaker damage from transient voltage. These modules include the P.I.P.-AMCb, P.I.P.-EDCb and P.I.P.-PA. While the P.I.P.-EDCb is most commonly used for general loudspeaker protection, the

1.0

1.2

1.4

1.6

2

2.5

3

4

5

6

7

8

9

10

12

14

16

20

25

30

40

Example: Impedance = 8 ohms. Peak Power = 75 W

Answer: Fuse = 1.5 A

LOUDSPEAKER IMPEDANCE (ohms) FUSE (amps)

20

15

10

8

6

5

4

3

2

1.5

1

.8

.6

.5

.4

.3

.2

.15

.1

.08

LOUDSPEAKER RATING

3000
2000
1500
1000
800
600
400
300	power)
200
150	average
100	continuousthe
40
80
60
30	4 times
20	(Typically
15
10
8	MUSICPOWER (watts)
6
4
	PEAK
3

2

1.5

1

P.I.P.-AMCb is very popular in systems that require a high-quality crossover, and the P.I.P.-PA is the proces- sor of choice for applications that require a microphone and line level input for each channel. And finally, the Smart Amp IQ-P.I.P.-DP provides both an input com- pressor for transient protection and a smooth output limiter for long-term thermal protection. For more infor- mation on P.I.P. modules, see Section 8.

3.4 AC Mains Power

All Studio Reference amplifiers are shipped with an appropriate line cord and plug. The 120 VAC, 60 Hz North American Studio Reference I has a special TT30P plug and includes a matching receptacle. Al- ways use an isolated power receptacle whenever pos- sible with adequate voltage and current. Excessive line voltages 10% or higher above the rated voltage will cause the amplifier to activate its standby mode (see Section 4.3.2). For example, do not exceed a 132 VAC with models rated for 120 VAC operation.

Unless otherwise noted, all specifications in this manual were measured using 120 VAC, 60 Hz power mains with voltage accurate to within 0.5% and THD of less than 1.0% under all test conditions. Performance

Fig. 3.16 Loudspeaker Fuse Nomograph

Page 18

variations can occur at other AC mains voltages and line frequencies. Line regulation problems will directly

affect the output power available from the amplifier.