Thanks John,
But, not being a genius, I think that the permanent solution for my 44 tonner will be a big gob of airplane glue on the coupler, to permanently glue it closed. I never do automatic coupling or uncoupling anyway.
Back to the original sound issue, is a Z-1000 a sine wave transformer instead of a chopped-wave transformer? If so, then one of these may solve the OP's problem.
Mannyrock