Sencore SP395 - Input Gain Control - Preamplifiers

SP395 SoundPro Audio Integrator Form7492 Operation Manual
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The audio output from the headphone jack and speaker is routed through separate output
monitoring circuits within the Integrator. Audio to the headphone or speaker is independently
switched on or off in the monitor part of the menu screen. The audio level output to the
headphone and speaker is controlled in the monitor part of the menu screen. Internal generated
audio or audio to the input jacks of the Audio Integrator may be routed to the monitor circuits.
Right, left, stereo, mixed (mono) audio may be selected. See the Bottom Toolbar section of this
manual.
Input Gain Control - Preamplifiers
The left and right audio inputs of the Audio Integrator feed into separate audio preamplifiers and
gain control circuits. These circuits provide audio measurement over a wide range of audio levels
and provide great sensitivity. There are thirteen gain ranges that are available to set the level of
both the left and right input audio signal. The gain ranges of the left and right inputs are
controlled independently in the top toolbar section of the test menu. See the Top Tool Bar
Section of this manual.
The selected input level or gain control setting establishes an overall amplification of the input
signal and best signal-to-noise ratio. The gain setting must be properly chosen for proper testing
results. You should select the range which provides the most amplification without overdriving
the sensitive input pre-amplifiers. The table below defines the clip points of each gain setting,
both in dBu and related for available standard microphones.
Clip Points Table
Gain Setting
Line Input
( dBu)
MIC-TP2
( dB SPL)
MIC-TP1
( dB SPL)
58 -45
52 -39
46 -34
40 -29 110 80
34 -23
28 -16
20 -9 130 100
10 1 140 110
-10 15 160* 130
-20 25 170* 140
-30 35 180* 150*
-40 45 190* 160*
* Beyond microphone maximum level
Note: To get the lowest SPL or noise levels you should use the maximum input gain setting
possible without clipping. In many cases this will be 42-58. At this setting you will have the most
sensitivity, but the input may clip at normal room SPL levels, depending on the sensitivity of the
microphone.
The Audio Integrator provides both manual and automatic range selection for the left and right
audio channels. The auto-gain function selects an input range for best measurement. If the input
level gets within 2dB of clipping, the gain is set to the next least sensitive gain (if possible). If
the input level is below that level at which the most accurate measurements can be made, the
gain is increased in steps until the maximum input gain is reached.