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Follow-up on: TV speaker amplifeir

Follow-up on: TV speaker amplifeir

Started March 1, 2013

When last we talked, you had recommended ferrite cores to keep RF interference from the wires.

I had bought a small 12 v audio amplifer. My input came from the earphone jack of my 12" tv, the output went to a set of phonograph speakers from a 1930's record player/radio, which were mounted above the bathtub between the bathroom ceiling and the wall. and the power came from an old wall wart.

The audio was indeed amplifed but a radio station also came out of the speakers.

I placed 2 cores around the input, one of them wrapped an extra time before he core was closed. One core around the output. I couldn't get the 4th core around the 12 v supply, so I put it around all the wires going into the amplifier. (Right next to the little black box the wires were thin, so I could do that.)

It didn't help. The radio still came through. In fact I could turn off the DVDR input to the antenna terminals fo the TV, and the radio came through loud and clear, with no tv interference of course..

So I gave up, opened the tv and removed the resistor to the earphone jack. Now I have the tv volume set all the way up and use the wall-mounted volume control to adjust the volume. Usually that control is set pretty low, and the sound seems fine, better than the one or two inch tv speaker that's for sure. Plus I don't have to use the remote control to adjust the volume.

I wanted the other plan to work, so it would with any tv I put in this spot, or elsewhere, since the tvs fail eventually. But I gave it a shot and I'm happy.

Thanks for all the help, in this project and the previous one.

Reply to
micky
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I would always use caution touching electrical in the bathroom, and never while in the tub.

Greg

Reply to
gregz

Which was already hashed out when he brought it way back when.

Michael

Reply to
Michael Black

Next time find the offending station's frequency and "trap" it out.

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Wave traps A wave trap is a tuned circuit that causes a specific frequency to be rejected. Two forms are used: series tuned (Fig. 2A) and parallel tuned (Fig. 2B). The series tuned version of the wavetrap is placed across the signal line (as in Fig.

2A), and works because it produces a very low impedance at its resonant frequency and a high impedance at frequencies removed from resonance. As a result, the interfering signal will see a resonant series-tuned wave trap as a short circuit, while other frequencies do not see it at all. The parallel resonant form is placed in series with the antenna line (as in Fig. 2B). It provides a high impedance to its resonant frequency, so will block the offending signal before it reaches the receiver. It provides a low impedance to frequencies removed from resonance. The wave traps are useful in situations where a single station is causing a problem, and you don?t want to eliminate nearby stations. For example, if you live close to an MW AM BCB signal and don?t want to interrupt reception of other MW AM BCB signals or LW

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Reply to
dave

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