Here is a method... first use a power converter from any electronic
device that uses batteries also... the converter will usually be
around 9 volts. Radio shack should have a DC reduction coil as most
dual units are not ac but DC ... they should also have a
ptotentiometer that will control the voltage and resistors if you
need to further lower the amperage use a combination of this and a
voltmeter..... if you like you can also hook an ammeter into the
circuit a dead radio often will supply what you need ... yard sales
are a good supply for this ... and if you know you electronics you
should be able to make what you need to plate out of one old radio!
as there are many resistors coils and the volume switch is a
potentiometer... all needed then is a voltmeter and for about thirty
bucks you can get a digital unit that works well for other uses
also..... like wiring and mechanics if you get my drift....
hope this helped....John Henry "Ringman''