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Portable mic modification help


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I have a small personal sound amplifier - essentially a mic with a headphone jack - that is powered by a single AAA bat.  I use this quite a bit and wanted to mod it so that I could plug it into the AC outlet.

I soldered wire to each bat terminal and then connected the wires to a variable AC adaptor. 

When set at 1.5V I get amplification similar to while on bat power but there is a terrible whistle.  If I bump the voltage to 3v I get less whistle but less amplification as well.


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I have never heard of a regulated  AC adapter with a voltage output of only 1.5V and a current output of only a few mA.

Why don't you use a rechargable Ni-MH battery cell? New AAA cells have a capacity of 900mAh which is the same as a new alkaline cell. The voltage starts lower but the average voltage is higher than an alkaline cell. They can be recharged one thousand times.

Get a spare rechargable battery cell so one is always fully charged.

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