What size amp would I need?

I asked before about a monaural amp for my bathroom TV, to use my cetiling/wall speakers from a 30's record player.

I hadn't been able to find a small amp, under 50 dollars on ebay or Amazon and that's why I asked here. Amazingly, then I found several in some other list (I'll try tell you later when I find it again.)

Now I'm ready to buy one but my question is, What size amp would I need? They ran from 5 watts to 14 watts and more. (The input will come from he earphone jack on the TV.)

And I presume I can take a stereo amp and connect the sides in parallel, if I keep polarity the same????

I have a 10" speaker and a 4 or 6" speaker, that I removed from

1930's record player, mounted to a suitable piece of chip board, covered with grill cloth (well, tan-colored burlap that a roommate had once used to cover the walls in his room) , and held to the wall and ceiling with hand-made molding. (not as fancy as it sounds.) I"m using the original crossover device (a single capacitor iirc. ) It gives a very nice sound. .

(It's been 30 years since I nailed all this to the wall, so I don't remember some details.

Thanks again.

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Beware of power ratings... or, at least, know what you're getting based on how the power rating is given.

It's been common for years to find amps and receivers marketed with extremely unrealistic power ratings... the classic example being the kind of amp which advertises "100 watts peak music power" but is driven from a wall-wart that might deliver 5 watts for a few seconds before overheating.

That's a good recipe for a fried amplifier, in many cases. Any mismatch between the two amplifier sides, *or* between the signals fed into the two channels will result in the two sections fighting with one another... one trying to pull the output voltage up, the other trying just as hard to pull it down. Each side will look like a dead short, or worse, to the other.

All it takes is one glitch, and all of the Magic Blue Smoke leaks out. Unless an amp is specifically designed and advertised as being able to handle this sort of parallel configuration, don't do it.

That being said... it's hard to give you a good answer to your question without knowing much more about the speakers you are planning to use, any enclosures, the volume level you want to run, the sort of program material you want to play, etc.

As a general rule of thumb, I'd guess that an honest 10-watt amplifier would likely give you as much volume as you'd want in this sort of application, unless your existing wall/ceiling speakers are extremely inefficient.

Dave Platt                                    AE6EO 
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior 
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Dave Platt

A true 5W -- that is, the amp can produce a continuous average power of 5W at low distortion -- should be more than enough.

I have large planar speakers, and you be amazed at how little power they need to play relatively loudly -- just a few watts.

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William Sommerwerck

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LOL. I'll pay attention to that. After I read your post, I noticed that the Radio Shack amp that gregz recommended said it used 25 watts input, but each channel had only 1.8 watts RMS. output.

FTR. so even an amp with supposedly identical sides might have some mismatch that would cause a failure.

In this case it would be the very same monaural audio output from the tv, and only a bad solder joint by me could make the two signals unequal. Might that be enough to damage the amp.


Two speakers from the 1930's, one 10" and one 6 or 4"

It's a rectangle about 2 feet by 1 footf set at a 45^ angle to the ceiling and the wall, and flush against the wall to the left. Open at t he right. I never got around to putting the side on the enclosure, because I didn't make provitsions to attach the side in the first place, and it r equires putting a ladder in the bathtub. And the sound is good enough.

Low I guess, because a) the rooom is small: b) the walls are either sheet rock or tile and there is the toilet, the sink, and the door but nothing soft like curtains. to absorb the sound, and c) for 25 years I used to run these speakers right off the earphone jack of the previous TV, which was a 12" B&W, tube TV** (not just the CRT, but about 6 or 7 tubes) .

**I paid $2 for it at a yard sale, it was 10 maybe even 20 0 years old then, and it ran for 25 more years without giving any trouble. It was "instant on" becaue they ran half-wave rectified current through the filamnts when the TV was off.

No concerts, just tv sitcoms and dramas, the Evening News (such as it is.) and Jeopardy.

They were typical speakers of the 1930's, but I don't know what that means. In the 70's I lived in an apartment building with several women in their 80's. So they had bought these things new, and now they were moving to what's almost as good as what's now called assisted living, although smaller, and they had no room for their radios, especially if part of it was broken. One end-table radio was from 1930 and it broke in 1940 and hadn't been turned on since then. She gave it to me in 1980 and I turned it on and it played beautifully. Unfortunately I haven't been able to get it run since that first time. (IIRC, I touched a screwdriver blade to a (anode?) cap on one of the tubes, but that only worked that one time.

Another woman gave me her husband's blackjack. He had been a military sentry in the Spanish American war. Most of the leather covering had falled off already, but at the time, before my mother gave me some of my granparents stuff (pots, a pillow) , it was the oldest thing I owned.

Thanks, and if you managed to read this far, thanks again!

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Thanks for the link and he extra effort to find the second link .

The first one sold last night for $10 plus 26S&H. The second one was cheaper and I'm thinking about it. It will do the job, I'm sure.

And thanks William.

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..... Thanks again. I learned a lot from this thread.

Gregz, I think yours would have worked well, but it was too small to sit under the tv, and took up too much needed space on top of the tv. (I have a radio and I forgot to mention, most of the time I have a wireless remote speaker from the compute( for Pandora; NPR podcasts, AOL radio (which no longer has a 50's or do-wop genre) etc.)

The other list I refer to I found again it and was Google Shopping, where I had used "small amplifier". The word small made a big difference. But when I went back to ebay, "small " made no difference, and with Amazon, it made things worse. It showed things but none that I wanted, none that were in google shopping.

So finally I found a use for Google Shopping.

It had several suitable but I ended up getting

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Provides 3.5W RMS output into a 4ohm load

If somewho it doesn't work, I'll get

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Provides 12W RMS output into a 4ohm load

Otherwise they are very similar. They both have line-in inputs.

(And I've bought from MCM i the past, before the web event. )

I had looked at my TV and it looked like it had stereo speakers, so I dl'd the manual to be sure, and the 24" inch version does have stereo but in the 13 inch version it's monaural, and it says 1Watt and 1 speaker. I should have done this in the first place, I guess, but I didnt' think of it.

So 3.5 watts should be more than what's there now.

The manual was useful for other reasons. For example, the tv has a setting where the speakers are off but the volume control controls the sound coming out of the RCA jack(s) in the back.

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