Filter
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5
Ultrasonic Filter
An ultrasonic filter is useful for minimizing RF interference, oscillations, leakage or aliasing from digital devices, and other signals that are too
high in pitch to hear but may wreak havoc in an amplifier system.
Program settings:
1. Set the jumper on Jx01 to enable the low-pass filter (across pins 2 and 3).
2. Set the jumper on Jx02 to bypass the high-pass filter (across pins 1 and 2).
3. Insert a resistor network in RNx02 that is appropriate to the desired roll-off frequency—
typically 16 or 20 kHz.
Typ. 16–20 kHz
Ultrasonic roll-off
Bandpass Filter
A bandpass filter may be useful if the speaker system driven by the amplifier has a limited bandwidth. Minimizing the out-of-the-passband energy
may result in reduced distortion and better intelligibility.
Program settings:
1. Set the jumper on Jx01 to enable the low-pass filter (across pins 2 and 3).
2. Set the jumper on Jx02 to enable the high-pass filter (across pins 2 and 3).
3. No jumper on Jx03.
4. Insert a resistor network in RNx04 that corresponds to the lower limit of the desired frequency passband.
5. Insert a resistor network in RNx02 that corresponds to the upper limit of the desired frequency passband. This frequency must be higher
than the one selected for the previous step.
CD Horn Equalization Filter
A constant-directivity horn requires a 6 dB per octave high-frequency boost from about 3.5 kHz to provide a flat frequency response. On the UF-3
you must use the CD horn equalization in conjunction with the high-pass filter.
Program settings:
1. Set the jumper on Jx01 to bypass the low-pass filter (across pins 1 and 2).
2. Set the jumper on Jx02 to enable the high-pass filter (across pins 2 and 3).
3. Set the jumper on Jx03 to select the EQ curve you desire: across pins 1 and 2 for +6 dB at 20 kHz, or across pins 2 and 3 for +10 dB at 20 kHz.
4. Insert a resistor network in RNx04 that corresponds to the desired low-frequency roll-off.
Subsonic Filter with CD Horn EQ
Use settings 1, 2, and 4 from the Subsonic Filter, and setting 3 from the CD Horn Equalization Filter.
This would be suitable only if the loudspeaker system uses passive crossovers.
CD Horn boost
Subsonic roll-off
Subsonic and Ultrasonic Filter
Use settings 2, 3, and 4 from the Subsonic Filter along with 2 and 3 from the Ultrasonic filter.
Typ.
20–50 Hz
Typ. 16–
20 kHz
Figure 6—UF-2 as an ultrasonic filter
Figure 7—UF-2 as a subsonic filter with CD
horn EQ
Figure 8—UF-2 as a subsonic and ultrasonic
filter