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IA18

A-SERIES INPUT AMPLIFIER & 24 dB/octave HP-FILTER MODULE


[IA18 photo] IA18 is a PP A-series balanced input amplifier and 24 dB/octave high-pass filter module. The module's voltage gain, filter slope, filter frequency and filter Q can be selected by the user.

IA18 installs in the location marked "INPUT AMPLIFIER MODULE" in PP products designed for A-series modules.
To suit most applications, IA18 is available in two standard versions : IA18A with electronically balanced input and IA18B with transformer balanced input.


IA18's electronically balanced input is a one OP-AMP instrumentation amplifier as this design combines low cost, low noise, low distortion and good common mode rejection ratio (CMRR), while the transformer balanced input uses a zero-field transformer as this approach reduces the transformer size by a factor of more than ten compared to the commonly used voltage driven transformer.
The transformer has a static shield for best possible CMRR and is housed in a mu-metal can to reduce magnetic interference.
The input amplifier's gain can be selected from -10 dB to 10 dB by replacing a single, socketed resistor.
IA18's high-pass filter slope can be selected to 0 dB/octave (filter off), 6 dB/octave, 12 dB/octave, 18 dB/octave or 24 dB/octave by 2 jumpers on the module.
The filter's frequency and Q are selected by inserting 8 resistors into sockets on the module. The filter topology used enables both Butterworth characteristic (maximum flat gain) and Bessel characteristic (maximum flat group delay) to be implemented.
IA18 Technical specification:
Specifications (except those marked (HP)) are measured with the high-pass filter off.
Specifications marked (HP) are measured with a 24 dB/octave, 30 Hz Butterworth filter.
All common mode voltages are referred to ground.
Specifications in [ ] are typical values.
THD+N meter bandwidth is > 500 KHz [80 KHz].
Unless otherwise noted, specifications are for 20 Hz - 20 KHz.
 
TypeIA18AIA18B
BalancingElectronicZero field transformer
Balanced input impedance10 Kohms ± 1 %10 Kohms ± 5 %
Maximum input signal21 dBu21 dBu
Maximum non-destructive input signal55 V RMS55 V RMS
Maximum common-mode DC voltage± 50 V DC± 100 V DC
Maximum differential-mode DC voltage± 100 V DC± 1 mV DC
CMRR @ 0 < Rs < 600 ohms, 20 Hz> 40 dB> 110 dB [115 dB]
CMRR @ 0 < Rs < 600 ohms, 1 KHz> 40 dB> 85 dB [90 dB]
CMRR @ 0 < Rs < 600 ohms, 20 KHz> 40 dB> 70 dB [75 dB]
THD+N @ 20 dBu input, 20 Hz< 0.002 % [0.0006 %]< 0.05 % [0.02 %]
THD+N @ 20 dBu input, 1 KHz< 0.002 % [0.0006 %]< 0.002 % [0.0008 %]
THD+N @ 20 dBu input, 20 KHz< 0.003 % [0.002 %]< 0.005 % [0.004 %]
THD+N @ 20 dBu input (HP), 20 Hz< 0.02 % [0.003 %]< 0.15 % [0.09 %]
THD+N @ 20 dBu input (HP), 1 KHz< 0.003 % [0.0006 %]< 0.002 % [0.001 %]
THD+N @ 20 dBu input (HP), 20 KHz< 0.003 % [0.003 %]< 0.01 % [0.004 %]
Voltage gain, 1 KHz± 0.4 dB [± 0.1 dB]± 0.4 dB [± 0.1 dB]
Voltage gain (HP), 1 KHz± 0.6 dB [± 0.1 dB]± 0.6 dB [± 0.1 dB]
Voltage gain (HP) (Q=1.5), 1 KHz± 0.75 dB [± 0.1 dB]± 0.75 dB [± 0.1 dB]
Linearity± 0.05 dB [± 0.03 dB]± 0.05 dB [± 0.03 dB]
Output noise, 22 Hz - 22 KHz RMS< -102 dBu [-102.5 dBu]< -97 dBu [-98.5 dBu]
Output noise, CCIR 468-2 Q-peak[-92.5 dBu][-88 dBu]
Output noise, A-wgt RMS[-105 dBu][-101 dBu]
Output noise (HP), 22 Hz - 22 KHz RMS< -100 dBu [-100.5 dBu]< -97 dBu [-98.5 dBu]
Output noise (HP), CCIR 468-2 Q-peak[-91.5 dBu][-88 dBu]
Output noise (HP), A-wgt RMS[-104 dBu][-101 dBu]
HP filter frequency range5 Hz - 70 Hz5 Hz - 70 Hz
HP filter Q range0.5 - 1.50.5 - 1.5
HP filter frequency tolerance± 3 %± 3 %
Supply current< 60 mA< 60 mA
Note:
The high THD+N figure at 20 Hz with the HP filter on, is due to the fact that the HP filter attenuates the 20 Hz fundamental by 14 dB, while its harmonics and noise are not attenuated.
When using the transformer balanced input module IA18B, care should be taken to avoid DC voltages across the input, as this will saturate the transformer and thereby increase the distortion figures considerably.

All specifications subject to change without prior notice.PP 940831

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