Is it suitable to use a 16ohm stereo headset on a 1000:8ohm audio output transformer?

Discussion in 'General Electronics Chat' started by ThirtyWest, Jul 15, 2017.

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  1. ThirtyWest

    Thread Starter Member

    Jul 15, 2017
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    Good morning, first time posting.

    Still trying to get a good education on the subject matter, so forgive me if questions are presented properly.

    --I have an aircraft intercom that puts out an audio signal with 600ohms. I do not have the power information for it--still looking.
    --Normal aviation headsets use 300ohm speaker cups (150 when in parallel).
    --I have a 1000:8 audio output transformer (found one remaining radio shack #273-1380 in my city) that does the job, but I'm wondering if I should be more specific since the headphones I'm using are standard over-the-counter 16ohm speakers.
    --This project is merely to solve the problem of finding FAR more comfortable ear buds and headphones in the consumer market than in the realm of aviation-related products.

    I'm having a tough time getting some general output transformer questions answered:

    1. Is the 1000:8 a range within which appropriately rated devices can be fit, or a ratio that is applied to whatever is sitting on each end of the transformer?

    2. Or, if I use 16ohm speakers does that mean it's effectively 2000 on the upwind side? I ask this because although the sound quality works VERY well, I've had to reposition the volume knob on the panel to a higher setting than where it usually sits.

    3. What does the 1000:8 mean when the incoming signal has an output impedance of 600?

    4. Should I be looking for a custom transformer with 600:16?


    Thanks in advance; I'll be researching in the meantime.
     
  2. LesJones

    Active Member

    Jan 8, 2017
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    Is the 1000:8 ratio the turns ratio or the impedance ratio ? The impedance ratio is the square of the turns ratio. The turns ratio is the same as the voltage ratio so you could inject a constant signal into one winding of the transformer and mesaure the voltage across each winding.

    Les.
     
  3. sumeryamaner

    Member

    May 29, 2017
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    A 1000:8 transformer is a fairly standart (but outdated) piece of hardware. It has 1000 ohms impedance at the primary and 8 ohms impedance at the secondary. As you are using a very low powered device such as a headphone, you can use it as long as the volume is OK for you. Btw I don't think that you will be able to find an audio transformer with an impedance ratio of 600:16 easily.
     
  4. ThirtyWest

    Thread Starter Member

    Jul 15, 2017
    36
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    Thank you both for getting involved here.

    Yes, 1000:8 is the impedance ratio. So, that would make a turns ratio of about 31.5 : 2.8?

    You say as long as the volume is ok for me. What wouldn't be ok? Do you mean, having to run the dial all the way with no increase in audio to my liking?

    If I were using something smaller like a 4 ohm headphone (as an example), THAT could cause a problem, correct?

    Back to the 600:16. Is it desirable to have the impedance ratio match exactly to the input and consumer? 600 from the intercom and 16 from my headphones?
     
  5. #12

    Expert

    Nov 30, 2010
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    There sits the proof of the pudding. You experienced exactly what you were told here. The impedance mismatch only diminishes the loudness and does not smoke the amplifier if your load is a higher impedance than the transformer.

    You're good. Go and sin no more.:D
     
    EM Fields likes this.
  6. ian field

    AAC Fanatic!

    Oct 27, 2012
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    In *EXTREME* cases; insufficient loading can allow excessive peak voltages on the primary side.

    A tube amp thrashed with no load can cause insulation breakdown in the primary windings, a solid state amp could potentially blow the output transistors.

    The under loaded output can shift more amplitude, so you get the appearance of only small power reduction.

    To be safe; you could parallel a 15R resistor so the amp is feeding closer to the intended load.
     
  7. ThirtyWest

    Thread Starter Member

    Jul 15, 2017
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    5

    1. Why 15?
    2. And you're saying insufficient loading, as in I've got 16ohm earbuds on the end but an 8ohm transformer?

    I thought the load was reflected?
     
  8. ThirtyWest

    Thread Starter Member

    Jul 15, 2017
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    I'm pretty sure this nintercom is solid state.
     
  9. #12

    Expert

    Nov 30, 2010
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    In EXTREME CASES!!!:eek:
    VACUUM TUBE AMPS!!!:eek:

    Fuggedabowdit.:rolleyes:
    This is not an extreme case and you don't have a vacuum tube amplifier.
     
  10. ian field

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    You assume too much.
     
  11. ThirtyWest

    Thread Starter Member

    Jul 15, 2017
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    Heh, it's definitely not a tube amp.
     
  12. ian field

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    Solid state is easier to damage.
     
  13. EM Fields

    Active Member

    Jun 8, 2016
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    In a roundabout way, yes. :) 1000:8 is a ratio of 125:1, so since the turns ratio is equal to the square root of the impedance ratio, the turns ratio would be equal to the square root of 125, or about 11.2.

    Yes, on a few fronts, but not knowing what your intercom's final looks like muddies the water.
    If your intercom is designed to drive a 600 ohm load, your load looks like 16 ohms, and the power transfer system must be kept passive, it'll perform at its maximum if an impedance matching transformer is interposed between the intercom's output and your load.
     
    Last edited: Jul 16, 2017
  14. EM Fields

    Active Member

    Jun 8, 2016
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    Not necessarily, since that depends on what the final looks like.
    Designed properly, it could be made very nearly bulletproof, but YMMV.
     
  15. ThirtyWest

    Thread Starter Member

    Jul 15, 2017
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    The "load" is normally 150ohm (two 300 ohm speaker cups in parallel).
     
  16. ian field

    AAC Fanatic!

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    Its starting to sound a bit like "100V line" that's often used to pipe muzak around factories. You can probably get off the shelf matching transformers for some of the common speaker impedances - probably easy to find a 3 Ohm secondary that should be fine with a 4 Ohm car speaker.
     
  17. EM Fields

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    Jun 8, 2016
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    But the TS wants to drive a 16 ohm load, so why is your suggested 3 ohm secondary relevant?
     
  18. EM Fields

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    Jun 8, 2016
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    That you could fool all of the people all of the time.
     
    Last edited: Jul 17, 2017
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  19. #12

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    That's why Ian is on my Ignore list. I only peeked this time because I have a dog in this fight.:oops:
     
  20. ian field

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    You side with the crazy hillbilly?!!!!!
     
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