Playing recorded voice with SPCM

13 thoughts on “Playing recorded voice with SPCM

  1. I have recorded voice sentence, composed by several words.

    The problem is that before and after palayng of each word, I can heard "click".

    How to remove it to have more smooth speech?

  2. Speech is generated automatically by speech to file program.

    Each word is in separate  file.

    Each file is converted to PCM insigned 8 bit, mono by GoldWave.

    Speech quality is not bad. I just need to remove clicking.

    After GL865, a audio amplifier TPA6204 (TI) is connected.


  3. I reduced speech to fit in one 16KB wav file, to have possibility to send it and "clicks" are not so bad.

    1. Hi,

      Do you connect the amplifier in single ended or balanced way? when audio part is opened there is a 400mv dump voltage on both line so in balanced way they eliminate each other

  4. Hi Luca,

    The power amplifier is connected with differntial input and output and both inputs are decoupled with 1uF ceramic capacitors as shown in Figure 16 in TPA6204 datasheet.

    1. Hi Nikolay,


      both EAR+ and EAR- line show a little voltage swing when audio section is enabled, from 1V to 1,4 V. This is usually not a big problem since the lines are balanced so the differential signal is null. I can measure a little (25mV ) voltage jump in the differential mode due to some difference caused by tollerance of component so the two lines are not perfectly uqual.

      The voltage jump is very fast and maybe this can be the real cause of the problem; I think you can try to lowpass filter the output of module ( probabilly just need to trim decoupling capacitor) to reduce the bump.

  5. Even if the audio section is enabled at module start-up and PCM sound is sent to speaker amplifier several minutes later, "clicks" appears at the start and end of consequtive dounds. So,  the problem is not caused by enabling audio section. You can check it.

          1. Are you mean that enabling speaker and speaker amplifier is not sufficient?

            What else to open audio path?

            AT#OAP maybe?