GC_ET_AFX_AFT.html
*** (Home)
AF"T" Roofing-Triad-Filter with a Single Hi-Q Filter
Emphasizing the Roofing Filters to supress the sidebands
*** Designed from building-block modules
*** Designed to be very easy to tune to f(700)
*** Designed so a single resistor controls f(0) on the Single Hi-Q Filter.
***
*** Triple Roof-Triad-Differential Filters preparing the signals
*** to drive a single Q=7 or Q=20 MFB bandpass filter
followed by switch selected Sharp Hi-Q Filters :
*** Last stage Q=7 MFB is 1400 Hz = -98 dB per octave.
*** Last stage Q=20 MFB is 1400 Hz = -110 dB per octave.
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*** PreAmp purpose
*** allows User Control on Initial Signal Level to circuit.
* (2) Higher drive forces Diode-Limiter into action.
*** Roof-Triad-Differential-Filter :
*** all sections with same f(0) and same components
*** design is very tolerant of minor component variations :
f( 585 ) cQ=3.0 R( 5800 )
f( 700 ) cQ=3.0 R( 4000 )
f( 830 ) cQ=3.0 R( 2800 )
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Roof Results: FIRST Roof Triad
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***
BW=325 Hz at -3dB
*** ie , 700Hz=0dB , 1400Hz=-26dB
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*** ie , 700Hz=0dB , 350Hz=-13dB
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*** SideBand FallOff is -26 dB per Octave;
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Roof Results: SECOND Roof Triad
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***
BW=325 Hz at -3dB
*** ie , 700Hz=0dB , 1400Hz=-54dB
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*** ie , 700Hz=0dB , 350Hz=-15dB
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*** SideBand FallOff is -54 dB per Octave;
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Roof Results: THIRD Roof Triad
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***
BW=325 Hz at -3dB
*** ie , 700Hz=0dB , 1400Hz=-75dB
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*** ie , 700Hz=0dB , 350Hz=-18dB
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*** SideBand FallOff is -75 dB per Octave;
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*** Option for Sharp Filter ************************
*** Final MFB filter, Q=7
**** -98dB per octave*** "N"arrow = mQ=7.0
*** BW = 100--225, v=14,
*** 1000 Hz=-45dB ,,, 1400 Hz = -98 dB
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*** Option for Sharp Filter ************************
*** Final MFB filter, Q=20
**** -98dB per octave*** "N"arrow = mQ=20.0
*** BW = 35--126, v= 10,
*** 1000 Hz=-75dB ,,, 1400 Hz = -110 dB
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*** Below : Schematic with an extra Q07 stage allowing a "before Roofing" and "after Roofing" comparison.
*** Triple Roof-Triad-Filter is 1400 Hz = -76 dB per octave.
*** Below : Triple Roof-Triad-Differential Filters. Most complex waveforms displayed.
*** This Bode Plot with two filters displayed in the central area,
*** allowing allowing a "before Roofing" and "after Roofing" comparison.
*** Notice that the Roofing Filters are acting strongly on the Yellow Trace, without altering the BandWidth. 
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*** Stage #4 MFB filter, Q = 20
**** -110 dB per octave
**** BW = 35--127, v=10
**** 1400 Hz = -110 dB
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*** Notice the Roof Filters pushing the Orange SideBands Down. 
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