DIY 2.1 channel amplifier not worked

Discussion in 'General Electronics Chat' started by Vaibhav Shinde, Jan 4, 2014.

  1. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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    Dear all,
    I am from one of the begginers in electronics hobbysists. I have some knowledge about electronics. I decided to build 2.1 channel amplifier with TDA7377 + LM4558D using schematic given on following site -

    Circuit power audio amplifier with TDA7377 2.1 – Stereo + Subwoofer 2x 12 Watts + 37 Watts | Xtronic Free Electronic Circuits and Informations

    Now, I have two 10w 4ohm satellite speakers and 50w 4ohm subwoofer. But after assembling circuit sound is anyway not coming. I am using 12v power supply. And usb mp3 player as sound i/p. But there is noise only. Please help me with this circuit. Whether LM4558D requires negative (-12v) power supply??
    Please help.....!!!
     
    Last edited: Jan 4, 2014
  2. wayneh

    Expert

    Sep 9, 2010
    12,123
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    Divide and conquer. For instance, can you verify that the 12V regulator is working and that the ICs have power? Is the audio signal reaching the input pins? One thing at a time.

    A photo of your build might help someone spot your problem. It's very easy to make a mistake, but it can be hard to spot one you made yourself.
     
  3. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Is this a tested = proven circuit?
    Is the PCB a commercial product or did you design it?
     
  4. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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    Dear friend,
    I have checked circuit connections. My regulator 7812 is working well. And output of 12 v is there. Also I have used usb mp3 player kit for audio input. And I am getting audio signal. I doubt whether LM4558 requires negative 12v supply or not. I am getting output noise but no music. I have installed circuit on general purpose PCB .So you may not get idea about connections , which I have made. Let it be, I will agin check connections again. You please help with any wrong design of circuit....!!! Please help..
     
  5. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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  6. absf

    Senior Member

    Dec 29, 2010
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    You can always make a simple audio oscillator using 2 transistors connected as an astable multivibrator or using LM555 to generate 800Hz tone and inject onto the TDA7377 inputs.

    If tone is audible there, then just go one stage in front of the TDA and inject the tone into the input of the op-amp and see if the tone disappears there. From that you can confirm whether the problem is in the power, main amp or opamp stage.

    Just my way of trouble shooting.

    Allen
     
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  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I don't see how it could work without a negative rail for the op amps. The non-inverting op amps have their inputs ground referenced. The input signals to them will be swinging above and below ground, so the signals would go well out of range.

    IMHO, the op-amp inputs would need to be DC leveled at 1/2 supply so they could handle input signals.

    I think it could be done by adding a 47k resistor at each + op-amp input (that has a 47k to ground) connected up to the 12V supply which would set the input at 6V. (?)
     
    Last edited: Jan 4, 2014
    Vaibhav Shinde likes this.
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    As mentioned the biasing of the LM4558 opamps is not correct.
    I have drawn 3 extra resistors and changed the values of 3 resistors to correct the bias problem.

    [​IMG]

    The changed resistors have red values next to them.
    3 of them need +12 Volts as shown.

    Bertus
     
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  9. Little Ghostman

    Member

    Jan 1, 2014
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    i dont want to hijack, but can i ask a quick question, why is 800Hz chosen? is it just a random value within the hearing range? and would a sine wave be better? just asking because i have a guitar amp to fix soon :D
     
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  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    With the 800 Hz, you can be sure the audio goes to the stereo channels of the amplifier and not to the subwoofer.
    Many subwoofers use a lowpass filter with a corner frequency between 150 and 200 Hz.

    Bertus
     
  11. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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    Thanks to every body. My circuit is running fantastic,. Now oly problem I am facing is, whenever I connect subwoofer in circuit, my all three speakers volume goes down & it produces distortion . Any help regarding this last problem???
     
  12. tubeguy

    Well-Known Member

    Nov 3, 2012
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    The sub woofer will draw extra current. Your power supply may be sagging.
    What is the power supply current rating?

    EDIT: Try it with only the sub woofer connected.
     
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  13. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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    Currently I am using 12v uniform DC power supply with 7812 voltage regulator IC. But TDA7377 IC has bridge mode output of 30 or 35 watt at 14 v. My sub woofer has 4 ohm 50 w rating. I will try your suggested option.
     
  14. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
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    Very much will depend of the power supply rating. In other words how much power it can deliver. If it is a commercial power. It should be labeled with both output voltage and how many watt it can output. Can you post those details ?
     
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  15. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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    Actually...I tried connecting only subwoofer , but only humming noise is coming. No bass at all. As far as power supply is concerned I have used RS 206L bridge rectifier IC followed by LM 7812. Another thing is my IC TDA 7377 is heating. Please suggest for Subwoofer & for heating problem.
     
  16. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Your bridge rectifier is to small.
    It is only rated 2 Amps.
    It might be that the buffer capacitor is also to small.
    What is your transformer rating?

    Bertus
     
  17. tubeguy

    Well-Known Member

    Nov 3, 2012
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    What is the DC voltage on each of the four outputs?
    Measure this at the IC pins, not after any coupling caps.

    The voltage regulator current is too small also.

    The IC's usable power output with low distortion is around 4+ watts for single-ended operation, and around 10 watts bridged for the sub-woofer, all @ 4 ohms load, if using a 14 volt supply, and somewhat less with 12 VDC.

    So, ball-park you need a few amps peak current from the power supply if you want to run the amp steadily near max power.
     
    Last edited: Jan 25, 2014
  18. jorge millan

    New Member

    Nov 9, 2014
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    Hello everyone. I made this circuit and also have the same problem with the subwoofer, I did the installation with the modifications gave bertus user and only have the problem with the subwoofer (30watt 8ohm) that distorts and does not sound good. Satellites sound perfect (2 * 10watt * 6ohm) but the general assembly has background noise and distortion that discourages me is the lack of bass. I'm using the bridge rectifier and OP.AMP KBU-802. MC-1558 and feed a computer power supply to test the circuit. In the forum creator circuit a person solved the sound problem in satellites making modifications to resistance but using 47k instead of 100k as proposed by bertus user and remove the problem of subwoofer replaced the regulator 7812 by the 7809 and I did and nothing happened. Please would any proposal to see if I can accommodate it. Thanks in advance
     
  19. Vaibhav Shinde

    Thread Starter New Member

    Jan 4, 2014
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    Jorge... There are following problems -
    1) IC LM 4558 needs dual power supply. I upamed my circuit to give +12V and -12V as well. Then I got sound in satellite speakers.
    2) Subwoofer filter section may have some wrong circuit. Which is causing noise & no output in subwoofer. I am studying the same.
    3) Circuit consists of number of components and & ICs. Hence it requires steady and large power.
    Circuit claims to give 30 W output. It means we need at least 12 V X 4A= 48W power supply for efficient operation.
    4) IC you mentioned later is 7809. This gives 9V. Which is not sufficient. Please note ,I had removwd both 7812 & 7912 ICs
    Used large current diodes and transformer to give better supply. Then my circuit worked.But subwoofer filter is still not working.
     
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