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sound board, completing the tromba circuit (nw) I'm not sure whether the model works properly or not, but in the circuit where it's used, I don't think it can work properly with the current TTL output model. A capacitor is charged by the Q output of a 74LS74 flipflop (U3A) until the voltage passes the Schmitt trigger's threshold, causing it to reset the flipflop. However, the positive trigger voltage of the Schmitt trigger is 1.6V, but our TTL output model has a high output voltage of 1.0V (see nl_base.cpp:89). I realise the simplified model of TTL logic with high impedance inputs and outputs behaving as though thery're loaded is convenient and fast to simulate, but it's not detailed enough for applications like this where 7400-series chips are used in analog circuitry. This is what held me up last time I tried adding a netlist for this sound board. |
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