Stereo amplifier with bass booster

Discussion in 'The Projects Forum' started by stringskipper, Aug 5, 2008.

  1. stringskipper

    Thread Starter New Member

    Aug 1, 2008
    Hi everebody! First of all i need to apologize on my english, it's not very good
    and if i make some mistakes i hope you will understand it
    I'm interested on some ideas about this project.
    (all solutions and diferences among them)
    I have allready started this and a i have some problems.
    The basic idea is to create audio amplifier which amplifies
    all audible frequencies, and add some circuit which will
    amplify bass frequencies. (few decibels). All with op-amps.
    So, the (ideal) amplitude characteristic will look like this -->(picture 1)
    (gain in bass range must be adjustable)
    I have create this circuit --> (picture 2, this is
    just one block, not stereo),
    but this don't do the work! I tried to place filter
    circuit in other part of feedback (parallel with R1, of course
    with changed values for R-C), but
    still it's the same result...--- no bass frequency change!
    I'm using LM1877.
    (I put these values just for the testing, so the critical
    frequency is set to 1 KHz. In real circuit i need to
    amplify frequencies from 30 Hz to 170 Hz, without loss of
    high frequencies and overall volume).
    I'm very grateful on all answers, ideas and explanations.
  2. bertus


    Apr 5, 2008
  3. Audioguru


    Dec 20, 2007
    Your schematic is a fuzzy JPG file type instead of a very clear GIF or PNG file type so I can`t reed the IC`s pin number.

    The inputs of the LM1877 must have a resistor connecvted to the bias pin 1. Pin 1 must have a capavitor to ground.

    The resistor from pin 7 to ground and pin 8 to ground must be in series with a capacitor to ground.

    These things are shown in the datasheet.