This effectively reverts b380514764 and
c24473ddff, restoring the state at
598cd52272.
Before pushing, please check that what you're about to push is sane.
Check your local commit log and ensure there isn't anything out-of-place
before pushing to mainline. When things like this happen, it wastes
everyone's time. I really don't need this in a week when real work™ is
busting my balls and I'm behind where I want to be with preparing for
MAME release.
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.
