Splitting an Audio signal for music system

Discussion in 'The Projects Forum' started by jj_alukkas, Jun 10, 2011.

  1. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Im assembling a small 2.1 music system with a built in usb/fm reciever and an aux input. I completed the amplifier for subwoofer along with its LP Filter and a stereo amp for driving small speakers. The problem I have is that I am unable to split the stereo audio channel between the sub's filter and the stereo amp. The filter has two 47k resistors on both channels which down-mixes it to mono before going to the filter ic for the subwoofer. If I connect the inputs of the resistors and the stereo amp's input together to the audio input signal in parallell, the output is too low. I think I need a splitter, so could anyone guide me on how to go for it? Preferring a passive and simple one. or should I go complex like this? http://freecircuitdiagrams4u.blogspot.com/2009/09/three-channel-audio-splitter.html

    Thank You :)
     
    Last edited: Jun 10, 2011
  2. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    After a lot of googling, I seem to need a 5532 to handle my stereo input as passives arent worth the job, can I run NE5532 on an unregulated +/-18v?
     
  3. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    No replies.. :( :(
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Be patient. this is an international forum, so replies can take upto 24 hours.

    What do you mean with ± 18 Volts unregulated?
    Is this without any stabelizer?
    If so, use a 78L12 for the positive and 79L12 for the negative line.
    (do not forget the decoupling capacitors at the stabelizers).

    Bertus
     
  5. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Oops Sorry, I was just a bit eager to finish my project. :(

    Unregulated, I meant 18v from a transformer with only filter capacitors. Anyway Im going in for a zenner/transistor based stabilizer as in the ckt diagram :)
     
  6. #12

    Expert

    Nov 30, 2010
    16,313
    6,817
    I think you answered your own question. The diagram you provided is a good one...except...that chip won't like a load of 110 ohms. I expect you can make sure the input impedance of your amps is high enough to avoid overloading the chip.

    You might use 2k audio taper pots for R6,7,8 to get better control.

    and yes, you can run that chip on unregulated voltage but why invite hum problems? Besides, +/- 18 is too close to the rated +/- 20 limit for the chip. I say, regulate it down to +/- 15 or +/- 12.
     
  7. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Thanks a lot for your reply!, and input impedance wont be a problem as I have 47k and 10k pot on the amps for volume control which should give them sufficient room I hope :)

    Also When I just started building the circuit, I realized I had got 18v zenners today as according to the circuit but my supply itself is 18v, so regulation wont be happening unless I get the zenners down to regulate to 12v :( If I change the zenners to 12v ones, would I need to change R4 and R5? also what wattage zenners do I need? Thanks a lot!
     
  8. #12

    Expert

    Nov 30, 2010
    16,313
    6,817
    OK. The 330 ohm resistors are only there to keep the opamp from smoking if a cable shorts to ground.

    Letsee...18V -12v = 6 across the resistor. If you use a 1/2 watt zener and run it at 1/4 watt it will want 20.8 ma.
    6/.0208 = 288 ohms but
    The regulating transistors will want a milliamp so you can use 270 ohms, 1/4 watt.

    Watch that math. You'll be using it for many circuits.
     
  9. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Ok, first point noted!

    Regarding the resistor, I read and did a lot of study over many pages and now I get the idea that the resistor is dependent on the zenner and not the load. :) so 6/(20.8+1)~270ohms right? :)

    And so I should be using 12v 1/2W zener and 270ohm 1/4w resistor right? So the minimum voltage the regulator was expecting as input is used to calculate the drop while max voltage used to calculate wattage :)

    Thanks a lot!! Learned something good which I didnt understand from the pages I read to learn it!!
     
  10. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Finally I completed my music system and my hearty thanks to #12.. The 5532 is an excellent chip, no hum or hissing and excellent gain for both the amplifiers. setting the minimum volume is enough for good sound, now have to add pots on both amps and wire it all into the sub box!

    Thank you again!!
     
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