Справочное Руководство для Crown studio reference i

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Studio Reference 

IIIII & II

  Professional Studio Amplifiers

SOLVING INPUT PROBLEMS

Sometimes large subsonic (subaudible) frequencies
are present in the input signal. These can damage
loudspeakers by overloading or overheating them. To
attenuate such frequencies, place a capacitor in series
with the input signal line. The graph in Figure 3.11
shows some capacitor values and how they affect the
frequency response of a 

Studio Reference amplifier.

Use only low-leakage capacitors.

For balanced input wiring, use an example from Fig-
ure 3.13. Filters A, B and C correspond to the
unbalanced filters shown in Figure 3.12. Filter D also
incorporates the subsonic filter in Figure 3.11.

Fig. 3.13  Balanced RF Filters

1. Use only shielded cable. Cables with
higher density shields are better. Spiral
wrapped shield is not recommended.

2. When using unbalanced lines, keep the
cables as short as possible. Avoid cable
lengths greater than 10 feet (3 meters).

3. Do not run signal cables together with
high-level wiring such as loudspeaker wires
or AC cords. This reduces the chance of
hum or noise being induced into the input
cables.

4. Turn the entire system off before chang-
ing connections. Turn level controls down
before powering the system back up. Crown
is not liable for damage incurred when any
transducer or component is overdriven.

Tip: The P.I.P.-FX has plenty of space on its circuit
board for the addition of input filter circuitry.

Another problem to avoid is ground loops. These are
undesired currents that flow in a grounded system and
usually cause hum in the output. A common source of
ground loop problems is the placement of input cables
parallel to power cables or near power transformers.
The magnetic field that surrounds these conductors
can induce the 50 or 60 Hz alternating current into your
input cables. To prevent this type of ground loop, it is
always a good idea to locate input cables away from

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Another problem to avoid is large levels of radio fre-
quencies or RF in the input signal. Although high RF
levels may not pose a threat to the amplifier, they can
burn out tweeters or other loads that are sensitive to
high frequencies. Extremely high RF levels can also
cause your amplifier to prematurely activate its protec-
tion circuitry, resulting in inefficient operation. RF can
be introduced into a signal by local radio stations and
from the bias signal of many tape recorders. To pre-
vent high levels of input RF, install an appropriate
low-pass filter in series with the input signal. Some ex-
amples of unbalanced wiring for low-pass filters are
shown in Figure 3.12.

Fig. 3.12  Unbalanced RF Filters

Fig. 3.11  Subsonic Filter Capacitors

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