biffloman Posted March 14, 2007 Report Share Posted March 14, 2007 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.Suggestions? Quote Link to comment Share on other sites More sharing options...
audioguru Posted March 14, 2007 Report Share Posted March 14, 2007 Maybe the circuit needs a supply bypass capacitor to work from the AC adapter.Maybe the AC adapter is a switching type that has its switching oscillator producing the whistle.Maybe the adapter has poor filtering and produces hum that you say is a whistle. Quote Link to comment Share on other sites More sharing options...
biffloman Posted March 14, 2007 Author Report Share Posted March 14, 2007 audioguruCan you suggest a better quality AC adaptor and a place to purchase onlineThanx Quote Link to comment Share on other sites More sharing options...
audioguru Posted March 14, 2007 Report Share Posted March 14, 2007 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. Quote Link to comment Share on other sites More sharing options...
MP Posted March 20, 2007 Report Share Posted March 20, 2007 Biffloman,Are you looking for something like this?http://www.amazon.com/Adorama-Regulated-Universal-Multiple-Connector/dp/B000AMCM5YMP Quote Link to comment Share on other sites More sharing options...
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