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mw8080bw: engine sound tone fix for 280zzzap netlist audio (#7028)

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Colin Douglas Howell 2020-08-02 19:35:58 -07:00 committed by GitHub
parent 8aa4963218
commit d35e103b9f
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2 changed files with 3428 additions and 691 deletions
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4088
src/lib/netlist/generated/static_solvers.cpp
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31
src/mame/audio/nl_280zzzap.cpp
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@ -89,11 +89,13 @@ static NETLIST_START(mc3340)
// amplify properly, generating only a very weak output signal.
// The 1990s schematics also omit a couple of diodes which are present
// in the 1970s schematics. One of these omitted diodes noticeably
// raises the minimum control voltage at which signal attenuation
// starts; that diode has been included here, to get the netlist's
// profile of attenuation vs. control voltage to better match
// Motorola's charts for the device.
// in the 1970s schematics. Both of these diodes have been included
// here. One raises the minimum control voltage at which signal
// attenuation starts, so it makes the netlist's profile of
// attenuation vs. control voltage better match Motorola's charts for
// the device. The other affects the level of the input "midpoint",
// and including it makes the engine sound closer to that on real
// 280-ZZZAP machines.
// The Motorola schematics do not label components, so I've created my
// own labeling scheme based on numbering components on the schematics
@ -134,9 +136,8 @@ static NETLIST_START(mc3340)
RES(R7_5K1, RES_K(5.1))
RES(R8_20K, RES_K(20))
// 1970s Motorola schematics have another diode just above what I call
// "R9_510"; this diode doesn't seem to affect normal operation much,
// so I've left it out.
DIODE(D2_MC3340, "D(IS=1e-15 N=1)")
RES(R9_510, RES_R(510))
QBJT_EB(Q3, "NPN1")
@ -171,7 +172,7 @@ static NETLIST_START(mc3340)
RES(R17_5K1, RES_K(5.1))
DIODE(D2_MC3340, "D(IS=1e-15 N=1)")
DIODE(D3_MC3340, "D(IS=1e-15 N=1)")
RES(R18_510, RES_R(510))
@ -195,9 +196,11 @@ static NETLIST_START(mc3340)
ALIAS(MC3340_INPUT, Q5.B)
NET_C(MC3340_INPUT, R8_20K.1)
NET_C(R7_5K1.2, R8_20K.2, R9_510.1)
// (This is approximately where the other omitted diode, which I've
// left out, would go.)
// Location of second diode present on 1970s schematics but omitted on
// 1990s ones. Including it is critical to making the tone of the
// output engine sound match that of real 280-ZZZAP machines.
NET_C(R7_5K1.2, R8_20K.2, D2_MC3340.A)
NET_C(D2_MC3340.K, R9_510.1)
NET_C(R9_510.2, GND)
NET_C(Q4.E, Q6.E, Q5.C)
@ -226,8 +229,8 @@ static NETLIST_START(mc3340)
NET_C(R15_5K1.2, GND)
ALIAS(MC3340_OUTPUT, R16_200.2)
NET_C(R17_5K1.2, D2_MC3340.A, Q8.B)
NET_C(D2_MC3340.K, R18_510.1)
NET_C(R17_5K1.2, D3_MC3340.A, Q8.B)
NET_C(D3_MC3340.K, R18_510.1)
NET_C(R18_510.2, GND)
NETLIST_END()