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  1. #1
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    ic 7294

    Hi!

    got a problem with a amplifier I built.

    the amplifier is the kit from kitsrus nr 106 :http://kitsrus.com/pdf/k106.pdf consisting mainly of the IC: tda 7294


    I get sound out of the circuit. BUT after a short while the sound deteriorate and gets very poor and distorted. if I disconnect the power and immediately connect again the sound gets clear but again distorted after a short while.

    if I turn up the volume on the input pins it also clears for a short while. why?

    anyone got any clues what this might depend on?

    I power it from 3st 12v batteries because its used in a portable soundsystem. I use the 2 pins called +34v and -34v but leaves out the middle 0v. I gues 0v is used for some kind of stabilising if using unfiltered DC current?

    Would be great with some support! my knowleadge of audio amplifiers are very limited.

    thanks! //L

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  2. #2
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    tda amplifier

    Quote Originally Posted by Linusswe
    ... I use the 2 pins called +34v and -34v but leave out the middle 0v.
    So you didn't connect IC1-pin4 (& R2, C2) to Gnd ? Could be dangerous for your elkos and (output) transistors!
    Quote Originally Posted by Linusswe
    I gues 0v is used for some kind of stabilising if using unfiltered DC current? //L
    No; it's absolutely necessary to connect Gnd. Failing this is likely the reason for your pb. Don't forget to insulate the IC from the heatsink (s. p. 2)!



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  3. #3
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    tda ic amplifier

    Hi erikl!

    thanks for your response!

    yes IC1 pin4 is connected to ground and also r2 and c2
    I didnt mean the pin on the IC but the power pins on the PCB! sorry about the confusion.

    so gnd on IC is connected to gnd on PCB but then I dont understand how I should connect ground to "DC gnd" because that and -34v is not the same.

    Im confused of the separation of -DC and gnd isnt that the same thing?



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  4. #4
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    Re: problem with amplifier built around ic tda 7294

    Hi,

    You should be using six 12V batteries ---- 3 to generate +36V and other 3 to generate -36V (not 34V). Centre point of 6 batteries which are connected in series is the ground point, with respect to which you measure +36V and -36V. Connect this ground with PCB ground.

    If you are using lead-acid battery, voltage can go as high as 13.8V under fully charged condition. That means maximum terminal voltage can rise upto +/-41.4V. Make sure that the IC can withstand this supply.



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