Connect with us

LPF,HPF,BPF design

Discussion in 'General Electronics Discussion' started by Jamesmeister, Mar 5, 2013.

Scroll to continue with content
  1. Jamesmeister

    Jamesmeister

    8
    0
    Mar 5, 2013
    im working with the design given specifications required for us to have.
    300 Hz (Low) -LPF
    1 kHz (Mid) - BPF
    4 kHz (High) - HPF

    Cut Boost (Av dB) ±12 dB

    Ive done my computations in LPF and HPF and i can show a graph using pspice that shows my computations are correct but INDIVIDUALLY. Meaning, i haven't used a summing amp yet to combine all of them. so here is a picture of the circuit of LPF and HPF (Individual)

    [​IMG]

    with the picture of the graph
    [​IMG]

    But if i connect both of them to a summing amp.
    [​IMG]

    graph looks like this: [​IMG]

    the gain should only be about 12dB. as far as i know Rf=Ri so the amp will become a buffer amp which is what i did in the summing amp. i dont know why it attenuated. help please


     
    Last edited: Mar 6, 2013
  2. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    First glance shows you have connected the outputs together! That's for sure wrong (and destructive).
     
  3. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    I am not clear as to what you ae trying to do.
    There is a filter design, which I can not find at the moment which gives out low, medium and high frequencies.

    There is a problem with your circuit in that the two amplifiers have their outputs connected together so they will be fighting each other. You need a resistor from each to your buffer output.

    Edit. Pipped at the post!
     
  4. Jamesmeister

    Jamesmeister

    8
    0
    Mar 5, 2013
    ive edited my post explaining what i want to do. help please. :(
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    It's best not to edit your post like that because it's hard for people to see what's changed.

    Apart from including the images, this seems to be the major addition:

    The summing amp has nothing to do with delaying the signal. It simply combines them together.

    Google summing amplifier and you'll see what you've done wrong.

    If that graph you show is what you want to get out, then the practical effect is to simply reproduce the input. However you've done only th red and yellow bits, not the blue bit.
     
  6. Jamesmeister

    Jamesmeister

    8
    0
    Mar 5, 2013
    i just showed what the links look like, for others to easily see the images.

    yes, i still haven't done the BPF yet(blue). so its not possible to have the output like that even if i input 3 signals of diff frequencies at the same time? because we are required to have a pre-amp (3 mic inputs 2 line inputs) and as far as i know, all of them are connected to a summing amp so they are of different frequencies right?
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    I see no reason why they would be different frequencies.

    I still really don't understand what you're trying to do.

    At first I thought you might want to adjust bass, treble, and mid-range individually. Now you say you simply want a preamp with 3 inputs that are mixed. No need for filters in that description.
     
    Last edited: Mar 6, 2013
  8. davenn

    davenn Moderator

    13,838
    1,952
    Sep 5, 2009
    why would they be ? ... sounds like you are just making a 5 channel mixer ... yes?

    That doesnt explain the need for filtering as you have done

    Were you really wanting to filter each of the 3 microphones in a different way ?
    if so, why ? ... it seems quite pointless, specially when you are combining the results from each mic and filter anyway

    Dave
     
  9. Jamesmeister

    Jamesmeister

    8
    0
    Mar 5, 2013
    this is what we are tasked to do:

    sorry if i lack knowledge about this. when we had a short discussion on tone control using james baxandall circuit (treble bass), what i understand is that it only function as a filter. i've seen james baxandall circuit with mid range but we are required to show COMPUTATIONS that's why i ended up planning to design with lpf, hpf, bpf. what do you guys suggest should i do? thanks for all your help!!
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    Why don't you look at the first part first. Do the mixer first.

    Then worry about the tone controls
     
  11. davenn

    davenn Moderator

    13,838
    1,952
    Sep 5, 2009
    OK

    As steve said ... work on the preamp stages for each of the 5 inputs ..... 3 mics and 2 lines

    Then look at tone control ideas

    The point you really missed in your tone control filters is that they are not variable
    so they really are not very useful
    in a normal sound system there are 3 styles of tone controls commonly used
    1) a single control swinging between bass and treble,
    2) two controls, one doing bass boost/cut and one doing treble boost/cut
    3) and finally multi-band controls, anything from 3 ... bass, mid-range and treble
    then right through to a full multi band graphic equaliser. I have seen some with up to 20 bands on professional mixing desks

    Dave
     
  12. Jamesmeister

    Jamesmeister

    8
    0
    Mar 5, 2013
    i cant find any reference with computations on it. but ill try to work on mixer circuit tom.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-