that stage. Assuming that the hiss has not always been there, this indicates defective electronics. Certain special- effects units are rather noisy, so compare with other users.
Crackles— defined as a “popcorn” noise. If the crackle persists during pauses in the program material, this indicates defective electronics and must be traced down using the above procedures. Crackles which occur during audio peaks or when the electronics are vibrated usually indicate bad connections.
IV: SPEAKER PROTECTION
4.1 BACKGROUND
Speakers have several limits which should not be exceeded for reliable operation. It is the user’s responsibility to determine these limits and operate the amplifier accordingly. We offer several ways to avoid unexpected accidents, but you must still select speakers of appropriate type and power capacity and operate them within their limits.
4.2 DC PROTECTION
The design of the 1100, 1200 and 1400 amplifier circuit eliminates the DC fault problem at its source, so no special protection is required. The QSC grounded collector output circuit is AC coupled and cannot pass DC to the load. The Model 1700 features a Load Grounding™ relay and special protective circuitry to protect the load from any DC fault condition.
All Series One amplifiers feature a low frequency
4.3 HORN DRIVER PROTECTION
The compression drivers used with horns for
In
Frequency |
|
|
500 Hz | 80 | 40 |
800 Hz | 50 | 25 |
1000 Hz | 40 | 20 |
1200 Hz | 33 | 16 |
2000 Hz | 20 | 10 |
3500 Hz | 12 | 6 |
7000 Hz | 6 | 3 |
Table 4.3 Horn Protection Capacitors. (Values in micro farads)
18