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ADAU1701 AUX_ADC volume control won't zero output

Question asked by Gordon on Jan 16, 2010
Latest reply on Jan 18, 2010 by Gordon

Hi all. I'm having a problem getting the aux audio adcs to turn the level down to zero with the adau 1701. The best I can do is about -36db which equates to about 40mv p/p. Basically what I have is a board with the processor on with the gpio pins out to a short ribbon which connects to a board with the various tone volume controls etc. I can disconnect the ribbon cable altogether and still have the same problem. I've reduced the schematic to something very basic, inputs connetcted to two AUX_ADCs and two Single slew ext vols, see attached schematic. There's no measurable voltage on the AUX_ADC pins. I've hard wired them to ground and sill no joy. If I remove the external volume controls and put in two "Single volume controls" I can reduce the output to zero using them. Here are some observations/tests I've done: If I: Zero input/output registers the output goes to zero. Mute the core, no change. Power down the audio ADCs output goes to zero. Mute the audio ADCs output goes to zero. Power down the audio DACs output goes to zero. Mute the audio DACs output goes to zero. Clear the EEPROM and manual reset output goes to zero. With everything connected and 'wired' as it's supposed to be things appears to work. Tone controls work, filters function, crossover works. There's a combined compressor/limiter in there as well but til I can get the volumes working properly I can't be sure it's working as it should. I've attached the basic circuit and eeprom output. Hope someone can give me some pointers with this, I'm tearing what's left of my hair out here. tia Gordon

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