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Thread: TDA7850 amp, anybody?

  1. #1
    Constant Bitrate tibimakai's Avatar
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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. #2
    MySQL Error soundman98's Avatar
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    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.

  3. #3
    Constant Bitrate tibimakai's Avatar
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    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?

  4. #4
    MySQL Error soundman98's Avatar
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    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..

  5. #5
    Constant Bitrate tibimakai's Avatar
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    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.

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    MySQL Error soundman98's Avatar
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    yup, that was something i forgot to mention, it is still a A/B amp, so it will warm up under normal operation..

  7. #7
    Constant Bitrate tibimakai's Avatar
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    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)?

  8. #8
    MySQL Error soundman98's Avatar
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    while i have not personally heard any 41hz kits, last i read/heard, most of their kits rate respectably in the audiophile community..

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    The holy grail of carpc FM radio, solved?

    Usb AMP with TDA7850 and Usb Automotive Grade FM Tuner

  10. #10
    MySQL Error soundman98's Avatar
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    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..)

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