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Thread: Car Amp Help!!

  1. #1
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    Talking Car Amp Help!!

    Hello all,
    First apologies if this has been covered but having spent ages looking I've finally given in and need some input. Even if its just pointers to the correct thread!?

    I am stripping out my headunit and from reading and research It appears I need an Amp to get the sound from the PC to the speakers via a soundcard.
    Now i know next to nothing about amps so can someone correct / enlighten me.

    Am I correct in assuming that the sound comes out of the pc as stereo, into the amp either as stereo or split into 2 sets of stereo streams then on to the speakers?

    Is there an issue with using a 2 channel amp into 4 speakers?

    Do I need a 4 channel amp?

    Could I use 2 2channel amps?

    I am keeping the stock speakers and am not after an amazing sound system, just a replacement to my car stereo running from the pc. I'll be happy if it is the equivelant of a mid range 4x50 system.

    Can anyone recommend me a cheap and more importantly small amp? (Looking at a maximum of about 30)

    Found this on Fleabay.
    http://cgi.ebay.co.uk/Mnew-car-boat-...742.m153.l1262
    Would something like this work or am I being a complete moron.

    Cheers all!

  2. #2
    Maximum Bitrate FusionFanatic's Avatar
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    Quote Originally Posted by thepurser View Post
    I am stripping out my headunit and from reading and research It appears I need an Amp to get the sound from the PC to the speakers via a soundcard.
    correct, if you not be using a HU then you will need to feed your computer's low-level audio signal directly into an amplifier.

    Quote Originally Posted by thepurser View Post
    Am I correct in assuming that the sound comes out of the pc as stereo into the amp either as stereo or split into 2 sets of stereo streams
    the first rule you have to learn before you even start your carputer project is... NEVER ASSUME ANYTHING!!!... now to answer your question; it depends on the computer/sound card and your software settings. if you're using a laptop or an OEM PC (HP, Dell, etc) then it will most likely have a single 3.5mm stereo output jack. if you're using a dedicated soundcard then chances are it will have at least 4.1 surround (4 separate channels plus a subwoofer output). using all 4 channels can be a pain to configure. even if you have 4+ channels available, it is often times preferred to set your sound card's settings to "2 speaker stereo" and simply use a y-adapter to split the 2 channels into 2x2 outputs (2 lefts and 2 rights, front and back play the same sound)

    Quote Originally Posted by thepurser View Post
    Is there an issue with using a 2 channel amp into 4 speakers?
    no, you simply wire two speakers to each output. remember to keep the speaker impedance within the amp's tolerance range. when you wire speakers in parallel you cut their impedance in half, when you wire speakers in series you double their impedance. when you lower the impedance you raise the amp's output power, when you raise the impedance you lower the amp's output power.

    most amps are 2-ohm stereo stable, so if your speakers are 4-ohms each you can wire them in parallel and the amp will see a 2-ohm load. since you are using your stock speakers, you need to find out their impedance before you can determine how to wire them up. if your amp is 2-ohm stable but your speakers are 2-ohms each then wiring the speakers in parallel will give the amp a 1-ohm load (which may burn the amp out), wiring the speakers in series will give the amp a 4-ohm load (which is fine).

    Quote Originally Posted by thepurser View Post
    Do I need a 4 channel amp?
    no.

    Quote Originally Posted by thepurser View Post
    Could I use 2 2channel amps?
    yes.

    Quote Originally Posted by thepurser View Post
    Found this on Fleabay.
    http://cgi.ebay.co.uk/Mnew-car-boat-...742.m153.l1262
    Would something like this work
    it would work, but don't expect spectacular or powerful sound from it. that 180W x 2 rating is complete BS (it is an unrealistic rating based on input/environmental conditions that your car cannot provide)... basically, the peak output rating is used purely for marketing reasons, it is a useless number in determining the actual performance of an amp. cheap amps emphasize the peak output, while good quality amps emphasize the RMS/continuous output. notice how they don't include the RMS/continuous output rating on that little amp?

    Quote Originally Posted by thepurser View Post
    or am I being a complete moron
    no, you're just learning. as long as you are willing to learn then there is no shame in not knowing something. I tried to explain everything as clear as I could, but if you still don't understand something, don't hesitate to ask

  3. #3
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    Aug 2006
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    Thanks FusionFanatic!!! Best reply I've ever had on a Forum. Really useful.
    Will have to go and have a look at my car speakers and brush off my Math skills. Aaarghh.
    I aim to basically use the CarPC as a replacement HU but with integrated Nav and Reverse Camera. Need to check but fairly sure the PC has just the basic outputs.
    Under these circumstances it would seem a 2ch amp would be sufficient?
    So if I find an amp that can output 2x 50w rms does that drive all four of the speakers (in two pairs) at 50w or at 25w each? (If the speakers are wired correctly for the amp and the Ohm levels are matched.)

    I should have known to "NEVER ASSUME"!!! It was the one thing I remember learning from my old Headmistress and the one mantra I kept repeating to my cast when I was a Company Manager. It came back to bite me a lot!!!

  4. #4
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    do i have enough power?

    if i have a 4 channel amp with 1,600 watts and i wanna power 2 kenwood subs that have 1,500 watts each and my stock front and rear speakers will i have enough power?! cuz i don't know how to do this kinda stuff yet i jus got all this stuff free and wanted to put it in my truck

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