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  • TDA7850 amp, anybody?

    anybody has any experience with this 4 channel amp(diy kit from ebay)?
    http://cgi.ebay.com/TDA7850-4-Channe...item3cb124b6a6

  • #2
    the data sheet tells more then the ebay link:
    http://pdf1.alldatasheet.com/datashe...S/TDA7850.html

    here is the real power specs:
    4 x 50W/4Ω max.
    4 x 30W/4Ω @ 14.4V, 1KHz, 10%
    4 x 80W/2Ω max.
    4 x 55W/2Ω @ 14.4V, 1KHz, 10%


    though i see this as a issue:
    Internally fixed gain (26dB)

    this means that there is no way to adjust how the amp sounds-- so if you were to add a sub amp to this, you would not be able to adjust both correctly..

    also, this line about standby is interesting as well:
    STAND-BY and MUTING facilities are both CMOS compatible. In absence of true CMOS
    ports or microprocessors, a direct connection to Vs of these two pins is admissible but a
    470kΩ equivalent resistance should be present between the power supply and the muting
    and stand-by pins.
    R-C cells have always to be used in order to smooth down the transitions for preventing any
    audible transient noises.
    About the stand-by, the time constant to be assigned in order to obtain a virtually pop-free
    transition has to be slower than 2.5V/ms.
    My OLD 2001 Mitsubishi Eclipse GT:
    "The Project That Never Ended, until it did"


    next project? subaru brz
    carpc undecided

    Comment


    • #3
      you are saying that I would have issues with it?
      I have researched on this a little bit and I didn't find to much. some RN510 clones and some Panasonic stereos are using these amps. I guess it would work for me also.
      but I'm open to any other imput.
      you now of any other similar amp?

      Comment


      • #4
        this is very similar to your memory questions: everything has a good purpose, and this particular amp design lacks, or requires more equipment then other car audio amps to get working..

        all car audio amps have a remote turn on to prevent power drain when the car is off. this amp design has a standby feature, but i am unclear on the exact things needed to make it work, but it does need more then just a switched 12v input..

        though another solution for powering this is to switch the main power, so the device has 0v going to it when the car is off..

        all car audio amps also have a gain control so that the amps can be correctly adjusted for input level-- this amp has a fixed level-- it might not be a issue right away, but if anything changes in your setup, you might need to adjust the input level on the amp, and with this amp, that might require more equipment to get everything to play nice..

        gain might be only something that you setup once or twice, but there is a reason it's there on most amps

        many members here have used motorcycle amps from ebay with good results-- and all of the ones i have seen have gain controls, and are usually under $50..

        in a quick search, i found this one, though there are many others listed there as well..
        My OLD 2001 Mitsubishi Eclipse GT:
        "The Project That Never Ended, until it did"


        next project? subaru brz
        carpc undecided

        Comment


        • #5
          thank you, it looks promising. most likely I will get that. though I need to mount it without the case. I will have to figure out another cooling method.

          Comment


          • #6
            yup, that was something i forgot to mention, it is still a A/B amp, so it will warm up under normal operation..
            My OLD 2001 Mitsubishi Eclipse GT:
            "The Project That Never Ended, until it did"


            next project? subaru brz
            carpc undecided

            Comment


            • #7
              you know anything about the 41hz Amp9? it would be a better choice?
              it is a good idea to install the power IC to the DD case(use the case as a comon ground, I will be using aluminum)?

              Comment


              • #8
                while i have not personally heard any 41hz kits, last i read/heard, most of their kits rate respectably in the audiophile community..
                My OLD 2001 Mitsubishi Eclipse GT:
                "The Project That Never Ended, until it did"


                next project? subaru brz
                carpc undecided

                Comment


                • #9
                  The holy grail of carpc FM radio, solved?

                  Usb AMP with TDA7850 and Usb Automotive Grade FM Tuner

                  Comment


                  • #10
                    for $160US, it doesn't look bad-- how much would shipping to the US be?(i can't read russian, so can't get further then adding to my cart..)
                    My OLD 2001 Mitsubishi Eclipse GT:
                    "The Project That Never Ended, until it did"


                    next project? subaru brz
                    carpc undecided

                    Comment


                    • #11
                      if you turn on Google translate it's a bit better, but there is a lot of bad translation also. I had the same situation when I've tried reading a wdtv player russian forum.
                      that amp it looks very promising. it's a bit expensive though(specially if I could build it myself too).

                      Comment


                      • #12
                        i think the $160 for the most-featured unit doesn't sound bad at all(something like $90 for the basic model)--- it includes all the software, allows for eq tweaks, and also has 2-3 aux inputs.. considering the amount of time it probably took to create the software, $160 isn't bad at all... i believe that 2k1toasters usb amp design was going to be shooting for the $300 mark...

                        i used google translate to get to the 'my cart' section, but many of the buttons that involved ordering and shipping were still showing in russian, so i couldn't continue..
                        My OLD 2001 Mitsubishi Eclipse GT:
                        "The Project That Never Ended, until it did"


                        next project? subaru brz
                        carpc undecided

                        Comment


                        • #13
                          I've also had trouble placing the order because I don't speak russian and google translate didn't translate that site properly. I've asked digitalcar.ru if he/they could provide sales via ebay instead.

                          I think that the tuner is recognised as an HID interface, which could suggest that it's found as an input device by the OS which I could then send keys to?? If that's the case then I would presume that this would work out of the box with linux and I am even willing to make an application port for it in linux.

                          I would also like to know how the ISO amp is seen by the OS? Did anyone find any details about the chipsets being used? For example, if the chipset is seen as a standard USB soundcard, there is a strong chance that drivers for it already exist in linux, which would make using it a easy. I believe that the TDA7850 needs an additional interface for it to be used in software, for things like volume, bass etc. If this is the case then is it interfaced by a specific protocol e.g. i2c/rs232? Is the USB hub in the ISO AMP Full powered only from the usb source or is it powered by an additional 5v converter inside the unit? Also, is it possible to split the 12v input on the Amp so that it can be connected to my existing carpc?

                          The ideal solution that I dreamnt of would have had the FM Tuner, Amp and possibly GPS+TMC units built into the main AMP (via USB hub) casing such that I could connect the ISO harness, antenna radio connector and power to that unit behind the dashboard, in a single tidy unit that will always remain in the car and only have the USB, VGA and power cables running to the trunk to the carpc. The carpc would then be accessible and easily removable for maintenance. Pushing the idea further, the unit could also provide regulated 12v and regulated 5v output such that the lilliput monitors can power from it. In fact, it would have been perfect if, on top of that, a single cable that transported VGA(extender), USB(extender) and power could be used as an output of the AMP(+FM+SOUNDCARD+GPS+VGA EXTENDER+USB HUB). This would then run to the carpc in the trunk and be split into VGA, USB, POWER(IGNITION, GROUND, Live) and even maybe the rear backup camera outputs for the lilliput. Then a shorter version of this cable could even be used to link into systems that are closer to the monitor such as the double-din bybyte casing.

                          Comment


                          • #14
                            Originally posted by kevinkga View Post
                            I've also had trouble placing the order because I don't speak russian and google translate didn't translate that site properly. I've asked digitalcar.ru if he/they could provide sales via ebay instead.

                            I think that the tuner is recognised as an HID interface, which could suggest that it's found as an input device by the OS which I could then send keys to?? If that's the case then I would presume that this would work out of the box with linux and I am even willing to make an application port for it in linux.

                            I would also like to know how the ISO amp is seen by the OS? Did anyone find any details about the chipsets being used? For example, if the chipset is seen as a standard USB soundcard, there is a strong chance that drivers for it already exist in linux, which would make using it a easy. I believe that the TDA7850 needs an additional interface for it to be used in software, for things like volume, bass etc. If this is the case then is it interfaced by a specific protocol e.g. i2c/rs232? Is the USB hub in the ISO AMP Full powered only from the usb source or is it powered by an additional 5v converter inside the unit? Also, is it possible to split the 12v input on the Amp so that it can be connected to my existing carpc?

                            The ideal solution that I dreamnt of would have had the FM Tuner, Amp and possibly GPS+TMC units built into the main AMP (via USB hub) casing such that I could connect the ISO harness, antenna radio connector and power to that unit behind the dashboard, in a single tidy unit that will always remain in the car and only have the USB, VGA and power cables running to the trunk to the carpc. The carpc would then be accessible and easily removable for maintenance. Pushing the idea further, the unit could also provide regulated 12v and regulated 5v output such that the lilliput monitors can power from it. In fact, it would have been perfect if, on top of that, a single cable that transported VGA(extender), USB(extender) and power could be used as an output of the AMP(+FM+SOUNDCARD+GPS+VGA EXTENDER+USB HUB). This would then run to the carpc in the trunk and be split into VGA, USB, POWER(IGNITION, GROUND, Live) and even maybe the rear backup camera outputs for the lilliput. Then a shorter version of this cable could even be used to link into systems that are closer to the monitor such as the double-din bybyte casing.
                            That FM radio only has a sensitivity of 2uv according to the datasheet. The original silabs dongle were 2.5uv, so with the Si4741 you are not going to see a drastic difference.

                            Infact the silabs which uses the headphone as antenna is much more sensitive, I think they can go as low as 1.1uv when connected to a proper antenna. Those silabs chip are used in mobile phone, I think sony ericsson still use them.

                            The DAB work very well in car, FM will be dead soon so why not go with the DAB/FM project? the FM tuner on the DAB project is 1.1uV or so. While a car radio sensitivity is 1uv or less.
                            Last edited by ibf; 05-29-2011, 11:56 PM.

                            Comment


                            • #15
                              Good point actually. Maybe the Amp + the DAB tuner would be a better combination. I think the DAB tuner seems to be controllable directly via the serial port too, just by sending some character codes. Sweet!

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