While a transducer may be more efficient with a sine wave, it's not obvious
to me that the overall system will be more efficient if you go to the effort
of generating a sine wave.  Generating a sine wave from digital electronics
means throwing away energy to get your analog levels, and if you want to
amplify that, you have to go to inefficient linear amplifiers instead of
nice clean digital switchs, and you throw away more power.

I don't suppose anyone has any actual data on this sort of thing?  Sound
output power (on a sound meter) vs overall current consumption, for instance?
(of course, class D amplifiers are all the rage now, because of their better
efficiency.  I guess these are equivilent to a switching regulator with fast
response to an external control voltage, right?)

BillW

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