Matching audio to speaker Z

Discussion in 'General Electronics Chat' started by powzoom, Feb 8, 2009.

  1. powzoom

    Thread Starter Active Member

    Jan 18, 2009
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    I'm trying to match the output of an audio amplifier to an 8ohm speaker but I don't have a transformer. I can't find them anywhere. Can I match impedance with a capacitor network? How can I do this?
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    If the amp has a low Z output, you may not need the transformer.
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    Maybe a transistor buffer can do the trick.
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    Sixty years ago, vacuum tube amplifiers used an output transformer to match the high output impedance of the vacuum tubes to the low speaker impedance.
    But modern transistor amplifiers have an extremely low output impedance so a transformer is not needed.
    Modern amplifiers do not "match" the speaker impedance. The extremely low output impedance provides excellent damping of resonances in a speaker.
     
  6. studiot

    AAC Fanatic!

    Nov 9, 2007
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    We still need and use transformers for 100V line distribution systems.

    We don't know the application here.
     
  7. powzoom

    Thread Starter Active Member

    Jan 18, 2009
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    Yea, like the one you posted studioT accept I don't have one of those. The circuit works and I can hear audio from the speaker but the volume is low. I tried it once before with the transformer and the sound increased but now I don't have that transformer and want to figure out another way to do it. Something like http://www.hoflink.com/~mkozma/match19c.html is what i was looking at but the site doesn't work for me. Its running off a battery so I can't just up the voltage cause its at its max now.
     
  8. studiot

    AAC Fanatic!

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    Unless you can explain your application in more detail I can't help further.

    An online network calculator doesn't tell me anything.
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    Is your amplifier lacking gain or is it lacking enough output power before clipping?

    The gain of an amplifier can be increased by increasing the value of one resistor, not by adding an output transformer.

    An audio amplifier is designed for a certain speaker impedance, usually 8 ohms.
    Some amplifiers produce more output power into 4 ohms and 2 ohms.
    A transformer might transform an 8 ohm speaker into 2 ohms so the amplifier has more output power (if it doesn't blow up).

    Please attach the schematic of your amplifier with its parts list.
     
  10. lespaul

    Active Member

    Jan 30, 2008
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    I am with audio Guru....the output of your amplifier may not have enough gain to crank the speaker. What type of speakers are you driving and how many of them do you have? Please send a schematic so we can check out your application.
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    A single-ended amplifier like an LM386 has an output at clipping into 8 ohms with a 6V supply of only 0.2W.

    But a TDA2822M amp IC is two amplifiers that are bridged and drive both wires of the speaker with over double the voltage swing of the LM386 and it doesn't need the huge output coupling capacitor of the LM386 circuit. Its output at clipping into 8 ohms with a 6V supply is 1.1W.
     
  12. italo

    New Member

    Nov 20, 2005
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    i AM JUST THINKING MAYBE THE TRANSFORMER WAS 4-8-16 Ω OUTPUT INPEDANCE TO MAX TRANSFER efficiency wise.
     
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