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  1. Old Comment
    abraxalito's Avatar

    TL431 output filter for TDA1543 current source elimination

    A quick look at the TDA1543A datasheet shows that with 890R from pin7 you'll get about 2.5mA out of pin7 through that resistor which translates to 5mA of bias. With 5mA of bias your I/V resistors should be 640R to get 3.2V as the maximum positive excursion. The negative going limit will be 1.7V. So you have 1.5V p-p or 500mVRMS.
    permalink
    Posted 8th May 2017 at 01:32 PM by abraxalito abraxalito is offline
  2. Old Comment

    TL431 output filter for TDA1543 current source elimination

    Hello Abraxalito,

    Thank you for taking care !

    Yes I tried with the very same I/V resistors.

    Here is my Vref schematic, I use a TL431

    Click the image to open in full size.

    In the mean time, I have read on a post that it might need to encrease Vref, right ?
    I don't understand how I calculate the current through the I/V resistors when using Vref.

    Thank you for your help.
    Best regards,
    Jean
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    Posted 8th May 2017 at 09:20 AM by Bidule Bidule is offline
  3. Old Comment
    abraxalito's Avatar

    TL431 output filter for TDA1543 current source elimination

    Hi Jean

    How did you create your 3.2V virtual ground? And you still use the same I/V resistors?
    permalink
    Posted 8th May 2017 at 02:40 AM by abraxalito abraxalito is offline
  4. Old Comment

    TL431 output filter for TDA1543 current source elimination

    Hello Abraxalito,

    I have made a Dac using one TDA1543 (PSU 5V) and decided to try to unconnect Pin 7 and to feed the I/V resistors with a 3V2 virtual ground.

    Click the image to open in full size.

    However, it doesn't work !
    Well,it is working, but I get a very weak level.

    When I connect back a 890 Ohms resistor between pin 7 and ground and the I/V resistors back to ground, it works fine.

    What am I missing ????

    Thank you for your help here.
    Best regards,
    Jean
    permalink
    Posted 7th May 2017 at 02:04 PM by Bidule Bidule is offline
  5. Old Comment
    abraxalito's Avatar

    Tweeter passive XO based on a transformer

    Thanks for the feedback! From what I recall about autoformers, they save a lot of copper when the turns ratio is close to unity but have smaller and smaller advantages moving away from that. Here as I'm going for at least 2:1 and probably 3:1 the advantage is fairly small. But might be worth considering if they show improvements in leakage inductance.
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    Posted 4th May 2017 at 11:01 AM by abraxalito abraxalito is offline
  6. Old Comment

    Tweeter passive XO based on a transformer

    Well that is a different approach!

    I remember seeing auto transformers used in some old XO's. That is essentially what you are doing here but instead running the full power through the core.

    You might want to look at the auto transformers approach - less flux and likely less distortion as a consequence.

    Nice off the wall idea.
    permalink
    Posted 4th May 2017 at 03:28 AM by googlyone googlyone is online now
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