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Audio Signal Conditioner Circuit

Last Updated on December 17, 2020 by Admin 4 Comments

This discussed audio signal conditioner circuit is great for sweeping weak and noisy audio or Morse-code signals. The circuit can also be utilized to clean up digital audio signals which are of the same frequency in a remote-control extender circuit.

How it Works

Referring to the circuit diagram below, the audio signal is attached through C1 and R9 to the input of U1 (at pin 3), which is a 567 phase-locked loop (PLL). The values of R1, R7 and C2 settle the detector’s operating frequency.

audio signal conditioner circuit

The moment a tone is recognized, U1’s output at pin 8 is attached to ground for the interval set by the input signal. If the audio wave is pulsed on and off, U1’s output follows in step with the input signal.

The output of U1 is supplied to the base of Q1, which is a 2N3906 general-purpose PNP transistor.

This BJT is applied to switch power to a second 567 PLL (U2) on and off. LED1 starts to flicker on and off in the same step with the coded input signal. Integrated circuit U2 functions as a set oscillator, producing a new steady-amplitude output signal.

There is no need for the enhanced tone to have the same frequency as the input.

However, it can be set to a different frequency using resistor R8. The circuit’s output frequency is dictated by R4, F8 and C4. Transistor Q2 is applied to separate the output of U2 at pin 5 via external loading.

The real values of frequency-determining components (as shown in the parts list) for this audio conditioner circuit permit the two PLL’s to tune from a low of a few hundred hertz to a high of several thousand hertz.

The simplest way to elevate or decrease the running tuning range is by increasing or lowering the values of C2 and C4.

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About Admin

Hey friends, Thanks a bunch for stopping by this site! I am an engineer with a Bachelor of Engineering in Electronics and Telecommunication. One of my passions is gathering information from all sorts of electronics books and tutorials. I then take that information and compile it into a language that is super easy to understand. My goal is to make those complex electronics circuit concepts and technical terms much more accessible for all the new and budding electronics engineers out there. I can also design customized circuit diagrams as required by the users.
If you have any questions related to this field, please do not hesitate to drop a comment! I am always here and ready to help you out with any queries you might have. I cannot wait to hear from you!

Reader Interactions

Comments

  1. day says

    October 7, 2024 at 3:59 pm

    hello admin,
    thanks for your feedback, however, how do I get the audio input frequency to match the U1 preset frequency values… any formula?
    Also does the said circuitry output audio or digital signal?
    please, kindly help out here to get it right.

    Regards
    day

    Reply
    • admin says

      October 17, 2024 at 12:39 pm

      R1, R7 and C2 decide the detector’s operating frequency, so can adjust these values until it matches the audio input frequency.
      Output will be digital….

      Reply
  2. Day says

    October 5, 2024 at 6:54 pm

    hello,
    the above audio “Signal Conditioner Circuit” was successfully assembled but no audio Signal output, when an audio Signal was applied.
    please, what could be the solution here.
    thanks as I look forward to your response via email.

    Reply
    • admin says

      October 7, 2024 at 12:48 pm

      Hi, the U1 IC will respond only when the input AF signal matches the frequency set by the U1 timing components.

      Reply

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