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1、BA716/717 INFORMATION GENERAL - (SEE FIGURE l) BA716 and 717 are fi xed together to form a sandwich assembly mounted near the centre of the channel or rev modules. A single l6 way fl ying fl atcable connector connects BA716 to a header on BA70. BA716/717 form a four band fully variable (parametric)
2、equaliser which may be switched into the Channel or Mixdovn signal paths. The high frequency and low frequency bands may be switched from a peaking to a shelving characteristic When used in a Rev module the EQ may be switched into the Rev Send path (or Delay Insertion path if INS button on BA752 is
3、pressed) or the Rev Return path. USER CONTROLS Frequency controls : one per band, marked 30Hz - 300Hz ; 200Hz - 2kHz ; 0.8kHz -8kHz ; 1.5kHz - 15kHz. Set band centre frequencies. Boost/Cut controls : one per band, marked LOW, MID 1, MID 2, HIGH. Set band boost or cut over range +l8dB. button : When
4、out, low band response is bell shaped. When in, lowband response is shelving. button : When out, high band response is bell shaped. When in, high band response is shelving. CH button : When out, EQ is available in the Mixdown path. When in, EQ is available in the channel path. IN button : When out,
5、EQ is bypassed. When in, EQ is inserted in the signal path. NOTE ; As with all parametric equalisers, a certain amount of overlap of frequency ranges is provided. Careless use can thus result in ridiculously high gains at certain frequencies which may cause oscillation. DETAIL See ET10209 (circuit d
6、iagram), EB2036U (channel module block diagram), and fi gure 1. The BA716/717 parametric equaliser may be considered to consist of fi ve separate sections, each of which is physically split between the two printed circuit boards: a) In/Out switching and LED indicator switching b) Low band EQ section
7、 c) Mid 1 band EQ section d) Mid 2 band EQ section e) High band EQ section All the EQ sections are connected in series. RadioFans.CN 收音机爱 好者资料库 INPUT/OUTPUT AND LED SWITCHING Switch SI (CH) on BA717 and S2 (IN) on BA716 enable the equaliser to be switched into either the Channel or the Mixdown signa
8、l paths, and to be either in circuit or bypassed. One pole of each switch is used to switch LEDS mounted remotely on BA7o. IC1 on BA716 is a non-inverting buffer amplifi er. LOW BAND EQ SECTION BA717 : IC1 amplifi ers a, b, and c, form a Two-Integrator loop fi lter whose frequency is tuned by RV1 (3
9、0Hz - 300Hz). The fi lter has a fi xed Q of 1 and its input is provided by IC2a on BA7l6. Two outputs are taken from the fi lter to a summing amplifi er ICld, one fi lter output and ICld output then going to the shelving switch (SI on BA716). BA716 : IC2b is used as an inverting summing amplifi er t
10、o combine the fi lter output, selected by SI with the input signal from IC1 buffer. RV1 devices a voltage which is somewhere between the full input signal (fully clockwise, full boost) and the full inverted and summed output of IC2b (fully anticlockwise, full cut). The output of RV1 is amplifi ed by
11、 IC2a and is the input for the fi lter on BA717. Low band EQ section output is taken from IC2b, and is the inp* for the Mid 1 EQ section (lC2d etc). MID 1 BAND EQ SECTION BA717 : IC2a and d form a modifi ed Two Integrator loop giving only a second order bandpass output from IC2d. The Q of this fi lt
12、er is 2 and centre frequency set by RV2 (200Hz - 2kHz). Filter input is received from IC2c on BA7l6, and bandpass output sent to IC2d on BA716. BA716 : IC2d is used to invert the Mid 1 EQ sections input signal, (from IC2b the lowpass EQ sections output) and add to it the bandpass fi lter output rece
13、ived from IC2d on BA717. RV2 derives a voltage which is somewhere between full input signal (fully clockwise, full boost) and full fi lter output minus input signal (fully anticlockwise, full cut). The output of RV2 is buffered by IC2c and provides the input for the fi lter on BA717. Mid 1 band EQ s
14、ection output is taken from IC2d and is the input for the Mid 2 band EQ section (lC3a). The signal at this point has passed through both Low and Mid 1 band EQ sections in series, each of which operate without interacting. MID 2 BAND EQ SECTION The operation of this circuit is identical to that of th
15、e Mid 1 band section described above. It use3 IC2b and c and RV3 (0.8kHz - 8kHz) on BA717, IC3 a and b and RV3 (boost/cut) on BA716. Input is received frcm IC2c en BA716, the Mid 1 sections output. Output is sent from IC3b on BA716 to the input of the high band EQ section. At this point the signal h
16、as been operated on non-interactively by the Low, Mid 1, and Mid 2 band EQ sections. RadioFans.CN 收音机爱 好者资料库 HIGH BAND EQ SECTION The operation of this circuit is similar to that of the low band EQ section described above except that different outputs from the Two Integrator loop fi lter on_BA717 (I
17、C3 a - d) are used in order to achieve high pass shelving characteristics when selected by S2 on BA717. Amplifi ers used on BA716 are IC3c and d. Input is received from IC3b on BA716, the Mid 2 EQ sections output. Output is sent from IC3c on BA716 back to the IN switch S2 on BA7l6. At this point the
18、 signal has been operated on by all four EQ sections in series, non- interactively. LEVELS The BA716/7 circuits are used at a nominal level of -lOdBu. D.C. SUPPLIES The BA716/717 EQ assembly runs from +18V regulated power which it receives from the BA712/713 or BA752/753 assemblies via BA7U0. TEST P
19、OINTS Test points are provided as follows on BA716. TPOV OV reference TP1 Channel path output from EQ TP2 Mixdown path output from EQ TP3 EQ input, after path selection and in/out TPU Signal after low-band EQ section TP5 Signal after Mid 1 band EQ section TP6 Signal after Mid 2 band EQ section TP7 S
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