Help reducing hum.

Discussion in 'The Projects Forum' started by TIP31, Dec 15, 2014.

  1. TIP31

    Thread Starter New Member

    Aug 17, 2013
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    I need help reducing hum in an amp project. I am using an lm386 as a preamp and I am using an lm1875 as the main amp but I am getting a very annoying buzz. What can help eliminate this?
     
  2. wayneh

    Expert

    Sep 9, 2010
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    The hum might be coming from your power supply. Try a battery and see if it gets better. If no joy, try shielding the inputs.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The lm386 is a crappy noisy amp.
     
    TIP31 likes this.
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    We can't help without seeing how you wired it.
     
  5. Rory Starkweather

    Member

    Jan 27, 2015
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    Another common fallacy. You are saying that, if you can't see it, the problem is too difficult to ever fix. It doesn't work that way.

    I'm nearly blind. I build and repair electronics devices. I've been doing that for more than 15 years

    If you can't stay current you need to get out of the life.

    I got perma-banned from Electronics Point for saying something very much like that. It will be very interesting to see what happens here.
     
  6. #12

    Expert

    Nov 30, 2010
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    Pretending to interpret other peoples statements into absolutes and then refuting your own imagination, rudely, will not get you Brownie Points here, either.
     
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  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    After reading this thread, I am going to "technically" agree with Rory (though his 3rd para was offensive...).

    But, Rory, some of us are not up to speed on these things (and have no need to be) and like to watch and learn. This is difficult for us who don't have your background.
     
  8. Rory Starkweather

    Member

    Jan 27, 2015
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    I'm sorry for being offensive. It's just something I'm really sensitive about. I'm 100% disabled according to SSA and also the VA but I get along fine . . . on some days. People who say they can't visualize things or can't do things while they don't have the problems I do, make me wonder. Is there something else wrong with me, or something wrong with them? I really am concerned about my mental health. I don't need the wind blowing while I am walking the plank.

    As to your second para, Civilization works best as a cooperative effort. So I am a nutcase about power supplies. Well there are probably a thousand things you know about electronics that I have never even heard of.

    So let's make a deal. If you need a power supply, I'll send you the circuit diagram and the specs. When I design a PS, the printed specs usually weigh more than the finished device. Several of them made me more money on the art circuit than the electronics circuit.

    I don't have the theoretical knowledge to build a perfect power supply. I spend a lot of time reading doctoral theses on the subject, But I only took the first three years of Calculus, so a lot of it is over my head. I want to understand it, but I don't have the background. Field theory baffles me. I hit a wall that I can't get over, but I'm willing to keep butting my head against it for a few more years.

    I need help, but I think everyone else does too. If you need help with a power supply issue, look for a specialist. The good ones will give you the schematics for free, with the specs. The ones that are crocodile mouth and tweety bird ass will sell them to you.
     
  9. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    I am thoroughly confused. Stepping out now.
     
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  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    @TIP31 , Please post the COMPLETE schematic.
    What are you using as powersupply?
    The LM386 is not a preamp, better use an opamp like the NE5532 or TL071.

    Bertus
     
  11. Rory Starkweather

    Member

    Jan 27, 2015
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    Me too. What did I do wrong?
     
  12. Rory Starkweather

    Member

    Jan 27, 2015
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    I've heard about the LM386 a lot, but never needed one for anything. I'm branching out a little now and I have a circuit that might need one. Advice? Would it be a good circuit with filtering?
     
  13. #12

    Expert

    Nov 30, 2010
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    You over-reacted to MikeML with a statement that seemed to indicate that you can discover any and all mis-wires, mistakes, and misinterpretations done by amateurs, without any drawings, and everybody else should be able to do that, or pack up and resign from electronics.
     
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  14. crutschow

    Expert

    Mar 14, 2008
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    Nothing wrong in particular. Just seems that your comments were out of sync with the OPs query, which didn't involve power supplies.
     
  15. Sinus23

    Member

    Sep 7, 2013
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    OP was last seen 21 Dec. Maybe he has fixed the problem or got busy doing something else.
     
  16. Rory Starkweather

    Member

    Jan 27, 2015
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    The problem with that is . . .? I do it because I have to, not because I want to. Why is it an insult to suggest that someone else might be able to.

    That's it. Before the ban hammer drops again, I'm out of here.
     
  17. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    You're right. Is it possible to get a big, flashing banner at top that says, "You're an idiot for resurrecting/continuing this thread!"

    With the new "alert" feature, I only see the new post, not the date of the original or last post -- at least not without making the effort to look.
     
  18. Sinus23

    Member

    Sep 7, 2013
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    Well I didn't notice that it was an old thread for 5 minutes myself. The lack of response from TS made me look at the date.

    But on the topic this thread has become. In my opinion it is in general easier to diagnose a problem when you have a schematic and a picture of the circuit. Otherwise it becomes like fixing a computer via telephone. It can get frustrating, leading to misunderstandings and in the end it is easier to come to their house a fix it from there or by remote access.

    Just my 2 cents on the matter.
     
  19. ronv

    AAC Fanatic!

    Nov 12, 2008
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  20. #12

    Expert

    Nov 30, 2010
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