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Useing single supply amp with split supply preamp?

  1. Jun 22, 2014 #1
    I just finished a preamp/active crossover using the lm833n

    but the amp I need to run it with is a class D single supply board.
    and so the ground on the board is just negative.
    Can I run my [high pass/ground/low pass] signal into this amp?
    they are sharing a 24v power supply though and if I connect the pre amp boards ground to the class d boards ground then I am just crossing ground and negative because the class d boards ground IS negative.
  2. jcsd
  3. Jun 22, 2014 #2

    jim hardy

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    No takers yet ?

    Basically you create a "fake signal ground" for the opamp at half the supply voltage.
    Then you use capacitors at input and output to block the DC.

    read the first few pages of this introductory application note from TI, it should get you started..

    http://www.eng.yale.edu/ee-labs/morse/compo/sloa058.pdf [Broken]

    or you can get a small DC to DC converter that makes dual voltage
    there's plenty of them around

    http://www.ti.com/lit/ds/sbvs014a/sbvs014a.pdf [Broken]

    but if you're an audiophile you may not want a switcher around your hi-fi gear.
    Hmmm but then - isn't class D itself switching?
    Please excuse the question - I'm an old 6V6 audio guy.
    Last edited by a moderator: May 6, 2017
  4. Jun 23, 2014 #3


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    You have three different voltage requirements, VDD, VEE and GND for the LM833. How do you solve that? (obviously you don't)

    You probably have an input capacitor into a divider in front of the LM833 to create a virtual ground. The output voltage is then 12V when there is no audio.

    Put a capacitor in series with the 833 output and connect it to the Class D amp. Connect the class D between 0 and 24V and move on. (It probably has it's own input capacitor, but I'd use an external one unless you know the input circuit.)
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