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What size amp would I need?

Discussion in 'Electronic Repair' started by micky, Jan 31, 2013.

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  1. micky

    micky Guest

    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.
  2. 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.
  3. gregz

    gregz Guest

  4. micky

    micky Guest

    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

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

    micky Guest

  6. micky

    micky Guest

    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
    Provides 3.5W RMS output into a 4ohm load

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