Audio Engineering Associates RP48Q Operating Manual - page 6
Setting the Gain
As with any piece of audio equipment, setting and maintaining proper signal levels are critical to
obtaining optimum performance: if the level is too low, you sacrifice noise performance; if too high,
you risk overload distortion. The AEA RP
48
Q provides an easy method for setting and monitoring the
system gain.
The Input Gain control (ref. #3) provides from +7 dB to +55 dB of gain for the preamplifier input
stage. The Output Gain control (ref. #4) adds up to another +19 dB of output gain, following the
Curve-Shaper circuitry, for a total of +74 dB of gain as measured from the input to the unbalanced
output TRS jack (ref. #14). At any gain setting, the balanced output at the XLR connector (ref. #15) is
+6 dB higher in level than the unbalanced output.
The LED level indicators (ref. #10) monitor the signal level at a point in the signal path just prior to the
input of the balanced output amplifier, which is the same point where the unbalanced output is derived.
The Green LED comes on in the presence of low-level signal; the Red LED turns-on when you are ap-
proaching -2 dB below signal overload or “clipping.” The Yellow LED varies in brightness between the
two to indicate the general signal level.
Start with the Output Gain control (ref. #4) fully clockwise and the Input Gain control (ref. #3) fully
counterclockwise. Then, with the microphone in position increase the Input Gain until the Red LED
turns-on when the soundsource is at its loudest. If the LED is illuminated too often or too long, reduce
the Input Gain control one step at a time until the Red LED illuminates only briefly at the loudest
peaks. Once this setting has been determined, reduce the Output Gain control to the 2 o’clock position.
This will provide you with a little extra headroom for an optimum setting of the gain of the microphone
preamplifier.
Note, however, that if you subsequently apply HF boost, you may need to reduce the Input Gain con-
trol correspondingly to avoid system overload.
Also remember, the energy and excitement generated during a performance guarantees that it will
always be louder than the rehearsal, so after determining the gain during the sound-check it is a good
idea to set the Input Gain control one or two clicks lower for the performance to allow yet a little more
margin for headroom.
Using the LF Filter
The RP
48
Q was designed to compliment ribbon microphones perfectly. AEA Big Ribbon
TM
mics deliver
sub-woofer lows, which the RP
48
Q, with response below 2 Hz, renders faithfully. Such strong low
frequency content can mask high frequency intelligibility, so the tunable LF filter was engineered to
reduce low frequency energy to appropriate levels.
Directional microphones when moved closer on-axis to a sound source become more sensitive to low
frequencies. This proximity effect, otherwise known as “bass tip-up,” becomes more pronounced the
closer the distance. With some large transducer microphones such as the RCA-44 BX proximity effect
begins at six feet and is extremely pronounced at a distance of one inch.