I need help with an audio amplifier.

Discussion in 'Analog & Mixed-Signal Design' started by ConstructionK88, Jul 28, 2018.

  1. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Thank you. Want you and everyone to know none of this will be wasted. I will be studying everyone's equations. Also what circuit were you referencing in this post?
     
  2. Audioguru

    Expert

    Dec 20, 2007
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    It hasn't been designed yet. Two complementary power transistors and two or three little NPN transistors.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    What @Audioguru means is that it doesn't apply to any one design. It is the basic analysis of any audio amplifier with a push-pull output stage.
     
  4. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
    148
    2
    If tip41/42 with c1815(have a lot of these as well) would work I'd create it. If you had an idea for a schematic I might be able to create it just from experiments with different values of resistors and caps.
     
  5. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
    148
    2
    As I asked Audioguru if you have a rough schematic I'll try to make it and see how it goes if it's possible with tip41/42 and c1815s. I have plenty of both.
     
  6. sghioto

    Active Member

    Dec 31, 2017
    528
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    Actually it has been! The "Lil Tiger"
    How many times do I have have to mention this.:mad: :)
     
    ConstructionK88 likes this.
  7. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
    148
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    AHHHHHHH! I WILL BUILD IT! ALSO I DON'T KNOW HOW TO MAKE EMOJIS ON HERE! FRUSTRATED AND HAPPY YALL ARE HELPING ME FACES!!
     
  8. Audioguru

    Expert

    Dec 20, 2007
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    The Lil Tiger in post #110 produces 5W into 8 ohms when powered from 24V but do you want to carry around four 6V lead-acid batteries?
    With two 6V batteries producing 13.2V I calculate an output of only 1.1W into 8 ohms because the design is using darlington transistors that have a lot of voltage losses.
    A 4 ohm speaker would almost double the power to 1.9W.
    Bridging two of these amplifiers would produce about 6.7W into 4 ohms with a 13.2V supply.

    Compound transistors should be used for less voltage loss and fewer diodes. Then it will produce much more power.
     
  9. sghioto

    Active Member

    Dec 31, 2017
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    The TS claimed he would use 18 volts. At this voltage the power out is just under 4 watts at 4 ohms
    SG
     
  10. sghioto

    Active Member

    Dec 31, 2017
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    That's true but is the example you posted correct? Seems like that would only work using a dual supply maybe. I can't find any examples of that type of output configuration.
    Below I posted a working circuit using a different compound configuration driven by a LM386-4, 2.125 watts at 12 volts and 5.5 watts at 18 volts with a 4 ohm load.
    SG
    EEE LM386 to TIP42,TIP41 driver.png
     
    Last edited: Aug 13, 2018
  11. bertus

    Administrator

    Apr 5, 2008
    18,682
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    Hello,

    I just came accross a weird schematic that uses an opamp as driver for power transistor (founs in electuur):

    Power Amplifier 6 Watts.png

    They claim an output power of about 6 Watts @ 0.01 %

    Bertus
     
    Last edited: Aug 10, 2018
  12. sghioto

    Active Member

    Dec 31, 2017
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    Doesn't seem like much power for a 36 volt power supply.o_O
    SG
     
  13. Audioguru

    Expert

    Dec 20, 2007
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    Boy oh boy I made a messy error on the compound transistors, I corrected it.

    Elliot sound Products has many audio projects and uses single supplies and dual polarity supplies on them. Some use compound transistors.

    Many power amplifier ICs have datasheets that show booster transistors at the positive and negative supplies for the IC like this one that produces 29W at low distortion into 4 ohms, or maybe 16W into 8 ohms.
     
  14. Audioguru

    Expert

    Dec 20, 2007
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    The problem with using an opamp or an LM386 power amp to drive emitter-follower transistors or compound transistors is that the opamp and LM386 already have the voltage loss of emitter-follower outputs. Then the voltage losses are doubled resulting in less output power.
     
  15. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
    148
    2
    I wouldn't mind bridging them for less battery weight, also i should have mentioned that when I said carry around, I really meant it'll be on casters like a rolling luggage bag. My apologies but I use 3/4in birch for all my "pretty" wood projects and that stuff is heavy. Most everything like you're used to seeing in prefab speaker boxes is particle board with a plastic or thin wood veneer making it very light. If I build it, it will be quite solid. So more batteries aren't an issue. Even with just 2 it'll weight around 30lbs. However if you know a circuit that would work about the same with a 12volt supply I'll try it as well.
     
  16. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
    148
    2
    Also I'm not sure what you mean by compound transistors?
     
  17. sghioto

    Active Member

    Dec 31, 2017
    528
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    Not really. The LM386 worked better than a single transistor driver. The output from the TIP drivers clipped before the output of the LM386.
    SG
     
  18. sghioto

    Active Member

    Dec 31, 2017
    528
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    See post 213.
    SG
     
  19. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
    148
    2
    OK wow. I have seriously been missing a lot of posts on my thread. I just read 6 I never got alerted to and never noticed and they are at the same time of some of my posts. I'm going to apologize if I've repeatedly asked the same thing over because I'm getting posts hours after the time stamp
     
  20. sghioto

    Active Member

    Dec 31, 2017
    528
    73
    Well when you get over 200 post it happens.:p
    SG
     
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