Quest Engineering QA 4004 Скачать руководство пользователя

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INST

ALLA

TION

Notes for better

ampliﬁer performance

• Ampliﬁer gain

The ampliﬁer should always be operated with the input
level controls set at maximum. The only departure from
this practice is where the internal ﬁlters/crossover is
engaged in a bi-amp conﬁguration, where it may be
necessary to turn down the high frequency side of
the ampliﬁer. If the ampliﬁer needs to be calibrated, to
match a mixer line level output, the gain switch on the
back of the ampliﬁer can be switched to the correct
line level.

The objective of correct gain settings is to have all the
segments of the audio chain from the preampliﬁer/
equalisers/compressors/crossovers matched to the
ampliﬁer. A test tone should take every link in the chain
to 0 dB or +4 dB at the same input level. This way, a
mixer VU indicator is a real visual clue as to how hard
the whole system is running and no single element will
be adding distortion before the system is at full power.

• High- and low-pass ﬁlters

The ﬁlter system in a QA series ampliﬁer is a basic
switchable high/low pass crossover. It can also be
used to ﬁlter out sub-harmonic low bass frequencies
the speaker system cannot reproduce and waste
ampliﬁer power. It is particularly recommended to
switch in the 35 Hz High Pass ﬁlter when the ampliﬁer
is being used to power band-pass type bass boxes.

The ampliﬁer can be used to power a bass system
without the need for an electronic crossover by
switching the high-pass to 35Hz and the low-pass to
80 or 110Hz. The input link A/B XLR connectors at the
back of the ampliﬁer will remain full-range, so a full-
range signal can be daisy chained to another ampliﬁer
or powered speaker.

• Ampliﬁer limiter

The switchable limiter is designed to prevent the
ampliﬁer from clipping or distorting, there by causing
speaker damage. It should always be engaged except
in the circumstance where the ampliﬁer is being used
in conjunction with an ampliﬁer sensing speaker
system controller.

Some brands of speaker system are designed to
be monitored and controlled by a dedicated system
controller that is wired directly to the output of the
ampliﬁer. These systems measure both the input
and output from the ampliﬁer and monitor the signal
for best results from the speaker system. To engage
the ampliﬁer’s limiter will interfere with the controllers
sensing circuit, so the ampliﬁer limiter must be
disengaged.

• The air intakes

The two ﬁltered air intakes have removable ﬁlters for
cleaning. The air intakes should be unobstructed and
allow the free ﬂow of air.

The ﬁlters should be removed and cleaned as needed.
Running the ampliﬁer without the ﬁlters will allow the
ampliﬁer to ﬁll with dust and foreign particles and could
void the warrantee under some circumstances.

SERIES

User Manual

Series

Power Ampliﬁers

User Manual