Well, last night, I finished the first draft of the amplifier for my bathroom tv speaker.
Thanks for the advice earlier
It works well** except for two problems.
A) Allong with the TV sound, it blends in the strongest AM station in town. The amplifer module I bought just has 5 unshielded wires coming out of it, and for the input, I used 20 inches of lamp cord connnected to a 1/8" phone plug, which plugged into the earphone jack of the tv. I guess the fix most likely to work is to replace the lamp cord with co-axial shielded cable. Right?
Or I could just wrap some kind of shielding around the wire that is there. Like heavy duty aluminum foil taped in place. Good idea. Easier becaue I wouldn't have to hunt for some shielded cable, or solder a phone little plug to the end. .
B) It's probalby much too loud. I have to turn the tv volume down from a maximum of 50 to about 15. Then let it get amplifed again by the amp. I'm figuring the TV output has less distorition, and that using it at low volume which then gets amped by this thing introduces distortion. (Though I caouldn't tell because the AM radio was too much of a distraction.)
The remedy for this seems to be to change wall warts. Right now I'm using a 12VDC, 500mA adapter, which I chose mostly because it was the first I saw in my box that had the end, the tip, cut off already. The spec says it can use 4.5 to 12VDC
**I'm using a Kemo M031N monaural amplifier module that sells for about 8 dollars at MCM Electrronics. Rated at 3.5 watts. I'm glad I didnt' get the 8? wattt version that was about 13 dollars.It's "box" is open on one side but filled with some sort of hard filling. It has 5 unshielded wires coming out of one side. Two for the input. And two for the speaker plus two for the power, which share one negative wire. Which makes 5 total.
I paid no attention to polarity, since it's a monaural output, but when I put in a shielded input, I could make sure that the shield is conected to what the instructions say is the ground, if it matters???
Unlike their drawing, I don't have the pot wired into the input, because the TV is 9 feet away from the bathtub. Rather it's in the wires that go to the speakers, from a 1930's record player, mounted above the tub (for the last 30 years.) .
Thanks.