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car stereo mains

Discussion in 'Electronic Basics' started by [email protected], Feb 19, 2006.

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  1. Guest

    How would I go about powering a car stereo from the mains? I'm guessing
    the most logical way is to get some sort of transformer to step down
    the voltage to that of a car battery. Is there an off the shelf
    device/transfomer that I can just plug into the mains and step down
    from 240V to 12V? (particularly with no additional soldering/wiring

    If anyone has any links/diagrams to anything like this please let me

  2. Chris

    Chris Guest

    Hi, Will. A transformer won't cut it -- transformers put out AC
    (alternating current) voltage, which will ruin your car stereo
    instantly. It wants direct current.

    You're looking for a 13.8VDC bench power supply. Since you didn't
    mention the power requirements of your car stereo, and you're on the
    other side of the pond, I'd suggest you look at the bench supplies from
    Maplin, and pick one:

    If you know the wattage of your car stereo, just divide by 13.8 to find
    the current requirement. (e.g. 60 watt stereo means 60 / 13.8 = 4.35
    amps. And, for car stereo use, be sure to size the power supply for
    continuous duty (it will be on and at volume for more than a minute).
    The biggest of these is only rated for 7 amps or 96.6 watts (13.8V * 7

    The ones with current foldback protection are helpful if you're
    repairing car stereos, or there's a chance of an accidental short

    If your stereo is more than 100 watts, you can look around and google
    something under "13.8V bench power supply". Try to get a "linear" or
    transformer-based supply. Units over 100 watts pretty much have to
    have a fan, which might be annoying.

    I had a great car stereo on my workbench with a 13.8VDC bench supply
    for many years.

    Good luck
  3. Guest

    Excellent. Thanks very much.
  4. The device you want is called a DC power supply. You will need to
    determine the current your car stereo requires, and get a power supply
    that can deliver at least that much.

    Peter Bennett, VE7CEI
    peterbb4 (at)
    new newsgroup users info :
    GPS and NMEA info:
    Vancouver Power Squadron:
  5. Phil Allison

    Phil Allison Guest

    ** First off - use "googlegroups" correctly.

    Do NOT simply hit reply !!!!!!!!!!!!

    Hit "options" and then "reply".

    That way we can see who you are replying to and about what.

    * Verrrrrry simple.

    Use a good car battery and a charger to keep it topped up.

    The cheapest & best way.

    A DC supply that can do as well costs MORE than your POS stereo.

    ....... Phil
  6. Guest

    It was a general reply.
  7. Chris

    Chris Guest

    Hi, Will. Sorry about that.

    I suppose the "elite" here have some unofficial rules, which us
    groundlings from Google Groups must follow. Most of it has to do with
    conforming to standards which will simplify things for newsgroup

    1) Always apologize for being a groundling. We are indeed children of
    a lesser god, and not worthy of taking up space on their store-bought

    2) In Google, you click on the "show options" link at the title bar of
    the post, then click on "reply". That will give you a formatted post
    with the entire previous post already shown (with the > character
    preceding each line, allowing the newsreaders of the gods to optionally
    obscure it). In days of yore, when 1200 baud modems ruled the earth
    and bandwidth was an important consideration, it was considered bad
    form to include all the stuff which had preceded. You just included
    enough to keep the conversation going. However, it's still considered
    good form to do some editing if it's getting long.

    3) It's considered good form to bottom post. This allows the person
    who's seeing the post appearing out of nowhere to follow the thread.
    That merans putting your response after the prior post, even if you
    have to summarize.

    4) Execeptions to 2) are typically made in cases of general short
    responses like OK, thanks, "plonk", &c. Yours was one of these, so I'm
    not sure where the other post is coming from.

    There are also unofficial rules relating to common courtesy. Groups
    which cater to newbies are assumed not to have people waiting to ream
    them for their ignorance. If they wanted that, they didn't have to
    post on a newsgroup -- they just could have gone to their mother-in-law
    and asked her.

    My bench stereo was an OEM from "the best car I ever had" -- a
    comfortable, loyal little Toyota Corolla that lasted forever. The 20
    watt OEM stereo lasted for more than a decade after the car wore out at
    almost 200,000 miles. It cheered me up quite a bit, not least because
    it had wonderful signal sensitivity, and good fidelity. The original
    owner paid a good price for the stereo upgrade. It was even easy to
    repair. A remarkable example of good engineering. Or, as the other
    post would say, a POS stereo. Whatever.

    Cheapie Automotive battery: 22 pounds
    Cheapie charger: 11 pounds
    Total cost 33 pounds

    Maplin XM20W 2 Amp Continuous 13.8VDC Bench Power Supply: 15 pounds
    Total Cost: 15 pounds

    Not only that, but you don't have to worry about disconnecting the
    charger during use, and reconnecting and recharging after use. The
    battery charger typically puts out around 15 to 16VDC, which stresses
    out the stereo if it's running hot.

    The economics change somewhat for higher wattage stereos, but there are
    other considerations. Running a stereo at 100 watts is a lot like
    leaving your headlights on. Your battery will deep discharge fairly
    quickly, which really isn't good for automotive batteries. You might
    improve on this by placing batteries in parallel, but that doubles or
    triples the cost, and has it's own set of problems. If the batteries
    are not perfectly matched, the one with slightly higher voltage will be
    doing most of the work, and will want to charge up the lower voltage
    battery. Not an optimal solution.

    Of course, if you're just repairing stereos, it _is_ more economical to
    pop a battery, put in a series fuse, and have at it. No cost at all,
    and after your stereo is repaired, just put the battery back
    (recharging if necessary). No cost at all. But I didn't get the
    impression you were repairing.

    Again, sorry. S.e.b. is supposed to be newbie-friendly.

    Good luck
  8. John Fields

    John Fields Guest

    No, they're just guidelines which we should all follow in order to
    make life a little easier for all of us. The recent problem has
    been that with the advent of Google groups an ever-increasing
    number of the truly clueless has invaded Usenet, to the detriment of

    Phil Allison is _definitely_ not one of the "elite" here, no one
    really is, and his behavior is far from what you might expect from
    the rest of us.
    Not really "standards", per se, just netiquette.
    Plus, you're not allowed to use sarcasm! ;)
    It came from a misanthrope.
    This is such a group, and newbies don't usually get reamed for their
    technical ignorance, the "motto" of the group seeming to be "There
    is no such thing as a stupid question here."

    What they might (and often do) get reamed for is attitude and
  9. Guest

    you can't blame Phil. He is annoyed at me for being a Pomme. His
    grandfather was a rapist.
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