On Thu, 15 Dec 2005 16:49:02 GMT, jimbo <jimREMOVE@xxxxxxxxxxxxx>
>Big voltages but relatively small current?
The piezo material looks like a capacitor, so
it only draws current when the voltage changes.
The currents are "low" compared to typical
magnetic-type transducers, but at 1000 V
there is still a lot of power.
>The suggestion of the horn tweeter appeals to me. Looks like 50W
>tweeters can be had for about $5 a piece from surplus sources. A
>cheap op-amp delivering less than 50W over a good frequency range
>might do the trick for initial testing--since I don't know what
>drilling rates commercial setups are achieving, I won't know how
>much better it could be. ;)
Note that "consumer" tweeters are typically
rated for the power of the overall music program,
not the power actually handled by the tweeter itself.
In a 50W system, most of the power is going to the
woofer and midrange. The tweeter itself is
probably seeing well under 10W. So don't
expect you can put anything close to 50W into this
>Apologies for this naive question: Big voltages ... can they be
>done using voltage multipliers after the amplification stage? Um,
>a cursory glance at simple voltage multipliers gives a few
One problem with voltage mutipliers (besides efficiency)
would be that they rectify while multiplying. So you would
need to impose your 40 kHz on a much higher carrier,
and do some tricks if you want a bipolar response.
Also, remember that the load is a capacitor, so whatever
you drive it with has to remove the voltage as well as
supply it when the input voltage changes. It's not like
a power supply that mostly runs at a fixed voltage and
just uses a bleeder resistor to discharge the output
caps on shut-down.
A simple transformer would make much more sense.
Electrostatic speakers use high voltages at low
currents, and they typically use transformer drive.
But all that assumes you can get hold of industrial
piezoceramic materials that need the high voltages.
The horn tweeters don't need (and can't handle) any
The industrial piezo material I messed with many years
ago was tubular, about 1/4 inch in diameter, designed
as a linear actuator. Seems like it would be ideal for
your project, except that the original device was not
intended for high frequency use: It was for positioning
microelectrodes under a microscope, so the power
supply wasn't anything too fancy in the response
department. The whole instrument was from a
company called Burleigh, which may not be in
business any more, and they bought the piezo
material from somebody else. (I got some
samples from a Burleigh engineer, but never
really got them to do anything on my own.)
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