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FDS 360 E-Card
20.7 FDS-360 E
Installation
The 360E board filters 3 and 4 are shelf type filters which can be configured as
High or Low pass cut or boost. Filters 1 and 2 remain the same as the
parametric EQ filters on the 360D board (See section 20.4 for further details).
The design idea for filters 3 and 4 is to provide gentle slopes which will
enhance or cut low or high frequencies. To obtain these results only 1 resistor
value is needed, and the frequency is changed using different capacitor
values, typically between 4.7n and 22n.
For high pass cut/boost, X1 + X3 is a resistor and X2 + X4 is a capacitor.
For low-pass cut/boost, X1 + X3 is a capacitor and X2 +X4 is a resistor.
If the 4.7K resistor is changed, there may be some interaction between boost
resistors R23 + R34 to R28 + R39 (See figure 20.13 for boost resistor values). If
this occurs, the values of R23 + R34 to R28 + R39 will have to be changes
accordingly.
On the PCB there are 6 positions for the boost resistors, set to give 1dB to 6dB
of boost. The resistor values which can be used with these are shown below.
R23 + R34 = 82K
R24 + R35 = 39K
R25 + R36 = 24K
R26 + R37 = 18K
R27 + R38 = 13K
R28 + R39 = 10K
Fig 20.13 Boost resistor
values
BSS currently use a software package called Analyser III to produce the results
for the EQ boards. If you want to check this out, it can be obtained from a
company called Number One Systems, at the following address:
Number One Systems
Somersham Road
St. Ives
Huntingdon
Cambridgeshire
PE17 4WR
England
Tel : +44 480 61778
Fax : +44 480 494 042
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