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Amplifier behind dash / kit amp ?

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  • Amplifier behind dash / kit amp ?

    Hi all,

    New car pc project underway since I've just changed cars... I'm planning to fit a 7" screen into a custom double din fascia so I don't have to cut up the dash at all. To go with this I'm going to need an amp as I'll have no where for the stereo to go...
    Can anyone suggest something that I can fit behind the dash for an amp? I am just running std speakers and ideally want the smallest amp possible.
    The sort of thing I am looking for is an amp that I can power from the ISO connector so I don't have to run extra cables etc.. and hopefully I can mount it in the double din sized void behind the touchscreen.
    So far I am considering a Mondeo amp (not sure how big these are) or some sort of Velleman style kit.. (not sure which I need)
    Any suggestions would be appreciated.

  • #2
    To barrow from another member:
    Originally posted by scott_fx View Post
    if you want a small form factor amp check out the www.41hz.com or get a piar of sonic impact t-amps and wire them with a relay. the t-amp will put out about as much power as a stock head unit. the 41hz amps are more powerful (for the most part)
    "In the beginners mind there are many possibilities, but in the experts mind there are few."- Shunryu Suzuki
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    • #3
      yep, 41hz will be the best option for small+power.

      However, i'd re-check your options.

      a traditional amp will fit below the passenger seat without any effort, and a nice small 2 chan amp (like 300w) will take up very little room.

      edit: of course that means extra wires but if your dash is like mine there really isn't a lot of room.
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      • #4
        david navone has a small 20 watt amp as well
        http://www.autosound2000.com/linedrivers.htm#20x20amp
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        • #5
          Thanks for the suggestions guys, I'd really like to keep it all up behind the dash if I can.
          The 41hz kits look really neat, could one of you knowledgable bods just confirm this would be ok to use in a car; http://www.41hz.com/main.aspx?pageID=130
          I presume I don't need anything extra.. just get the kit and build it ?
          Also would anyone know how warm this kit is likely to get, that is my one concern about putting something behind the dash.

          Thanks for the help!

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          • #6
            Hi Swift_Gti,

            I'm using an AMP32 kit in my carpc right now. You will need a heatsink as a bare minimum. Additionally, I'd suggest a regulated power supply of some sort. You don't want to spend all that time building the kit just to fry it in an overvoltage situation. My AMP32 is being powered from the 12v line of my M2-ATX along with my LCD, though my mobo is a low power embedded board, so I have the wattage to spare.

            My setup has the entire carpc in a gutted, OEM 2DIN chassis. I bought and assembled 2 of the AMP32's, but I am only using 1 at the moment. The OEM chassis has a large, cast aluminum backplate and I have the amp mounted to that for heatsinking with no problems so far.

            Another issue I had with the AMP32 was the BIOS POST beep. My BIOS beeps at the end of the POST routine no matter what. The beep is played through the built-in mobo speaker, but it is also played on the soundcard output at full volume. This means that if the amp is powered when the mobo boots, you get an ear shattering beep every time.

            The AMP32 has a mute jumper. Short the jumper and the amp is on. Disconnect the jumper and the amp is muted. As I recall, the jumper completes a circuit to one of the input pins on the IC. So feeding a standard 12v amp-on signal (like the M2-ATX provides) doesn't work so well. I ended up using a transistor wired to the serial port DSR line and the amp jumper. Using the AmpCtrl service (do a search here), the amp stays muted until the OS fully boots. No more deafening beep.

            My car is a 92 Miata (wife won't let me gut the '02) and I normally drive around with the top down. I'm only using 1 AMP32 because my mobo only has 2 channel audio. That said, the AMP32 has more than enough power to get the job done. The volume control has never gone above 50% in my car, even at 70+mph with the top down.

            pb

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            • #7
              Wow, excellent info pbarrette - really useful stuff!
              I'd be very interested to learn more on exactly how you wire up the DSR to these amps.

              One thing.. may seem silly but amps aren't my strongpoint!
              I am using my std car speakers (1 pair of component speakers up front, 1 pair of component speakers in the rear..) what is the best amp to use?
              My audio feed is just a set of stereo RCA jacks (one red one white) do I need a 4 channel amp (like the Amp9) or will a 2 channel work (like the AMP32) - is there an advantage of using one over the other ?

              Thanks for the great info.

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              • #8
                I built AMP9 and it doesn't get hot. You need heatsink, but it's not warming up with my usage. I'm planning on using it in my CarPC (dual DIN)

                Right now I use iPod as a source and power AMP9 from my Car's stereo jack (15A line)
                This chip designed for automotive use and fine with unregulated power.

                I have one extra 27V version that I can sell. It's tested and working.

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                • #9
                  Originally posted by swift_gti View Post
                  One thing.. may seem silly but amps aren't my strongpoint!
                  I am using my std car speakers (1 pair of component speakers up front, 1 pair of component speakers in the rear..) what is the best amp to use?
                  My audio feed is just a set of stereo RCA jacks (one red one white) do I need a 4 channel amp (like the Amp9) or will a 2 channel work (like the AMP32) - is there an advantage of using one over the other ?
                  You will need 4 amplified channels for 4 speakers. Since you have stock stereo - 2 AMP32s will do nicely for you. 25W per channel should be plenty. AMP9 gives 4 channels and have about 60W per channel on 12V and 4Ohm speakers. This is good to play more powerful components.

                  I split each chanel to 2 inputs on AMP9 and then feed each speaker individually.

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                  • #10
                    Thanks for the info Katit, I'm planning to do the same thing in terms of wiring up power etc. Is there anything in the instructions that get sent through regarding current drain? I would imagine the existing wiring harness in the car is fine but I don't want to fry anything
                    Thanks for the offer of the AMP9 kit, but I think I'm going to get the 12v version due to the lower profile.

                    Cheers

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                    • #11
                      Originally posted by swift_gti View Post
                      Is there anything in the instructions that get sent through regarding current drain?
                      That is something I'm not sure about. I think I've seen something like 10A on peak. But I will have CarPC with LCD also. I'm planning on dedicated 30A circuit for power. But I will use factory harness for speakers, antenna, etc.

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                      • #12
                        Excellent, thanks for all the info everyone.

                        Just going to order the AMP9 kit now

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                        • #13
                          Hi Swift_gti,

                          The Ampctrl service raises the DTR (not DSR, sorry) on the serial port of your choice. The DTR line is Pin-4 on a DB9 serial port, or Pin-20 on a DB25.

                          Stop by radio-shack and pick up any simple NPN switching transistor. Like this one.
                          The mute switch jumper has a + side and a - side. Use a multimeter, or check the amp schematic to figure out which is which.

                          Transistor hookup goes like this:
                          Base -> Serial port DTR (Pin4)
                          Collector -> Mute +
                          Emitter -> Mute -

                          Transistors with a TO-92 case usually have the Base as the center pin. If you accidentally reverse the collector and emitter, nothing is likely to break or get fried, your amp just won't turn on. If that happens, reverse the transistor keeping the serial port DTR wired to the center pin.

                          When you start the ampctrl service, the amp should turn on. When you stop the service, the amp should turn off.

                          Hope this helps.

                          pb

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                          • #14
                            Cool, thanks for that!
                            I've got a transistor like that laying around from another project so I will have a play once my USB > Serial convertor arrives

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                            • #15
                              Hmm.. well I've tried the suggested and it works fine when the PC is on, but as soon as the DTR signal is set low by the software then I just hear fast ticking through the speakers
                              Any ideas?

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