What is this offset for?

Semiconductor Integrated Circuits (ICs)
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What is the functionality of this offset trimmer? And how do you check if it’s calibrated correctly? This is a crossover audio

immagine
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Hi frekkia,

The OFFSET trimmer is used to adjust the dynamic rage of the LF353 to maximum. According to the LF353 datasheet, the output voltage range is symmetrical, thus the maximum dynamic range is reached, when the output dc-level of LF353 is zero.

The good old LM13700 is used as current (or voltage) controlled gain stage. I guess the calibration procedure is:

  1. Set the “Volume” to maximum (cannot see the whole schematic, but assuming that there is a potentiometer or DAC somewhere delivering the adjustment current to LM13700 pin 16.).
  2. Set the GAIN trimmer to maximum.
  3. Have no input signal.
  4. Adjust the OFFSET until the output pin 1 of the LF353 reads 0V.

I hope this helps, Cheers,
heke, AsamaLab

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Thank you Heke. Happy New Year :tada:

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