Improving Zipper Noise for AD5280

Hello, 

I am exploiting the AD5280 for managing phisical parameters of an analog audio processor for guitar.

the device works with presets ( abrupt change in the configuration: Gain, Boost, Master volume) . In addition these parameters can  be updated very fast with and ADC connected to a potentiometer (expression pedal).

this is a potential cause of zipper noise.

The proposed solution with a window comparator cannot be exploited because we are forced to use a dual supply. What solution do you suggest in order to address this potential issue?

Best regards, 

G

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  • Hello, 

    Here's the relevant part of the schematic.

    thanks, 

    G.

  • 0
    •  Analog Employees 
    on Sep 18, 2020 1:24 PM 7 months ago in reply to gZoppi550

    Can you explain with a block diagram where you are looking for an alternative solution.

  • Hello

    Here's what I mean.

    If I want to modify any parameter ( in this example just the volume) with an external knob, very fast and very frequently, I believe there's the possibility that noise might be generated  along with the process.

    what are your recommendations in order to have something as much robust as we can?

    Working with I2c we cannot easily isolate the various stages with gating, so we are going to have two noise contributors: 

    discontinuous steps with the digipot and I2c Switching noise coupled with every device.

    Thanks for your support.

    BR

    G.

  • 0
    •  Analog Employees 
    on Sep 22, 2020 4:54 AM 6 months ago in reply to gZoppi550

    What is the issue with single supply option?

    I have requested for the block diagram of the schematic to understand where you wants to have the digipot.

    Block diagram shown above does not correlate with the schematic as it does not convey the information that you are seeking here.

  • Hello, 

    The block diagram below (I hope it is clear now) represents the part of schematic I'm interested in

     

    the digipot is DC decoupled and is supplied with a dual rail.

    I can exploit a window comparator in order to intercept the zero crossing for a jump in the pot wiper: (E.G jumping from 10 to 100!

    My other question is about the effect of a continuous modification of the wiper ( e.g ) if the wiper is linked to the ADC's input voltage which is generated by a variable resistor (e.g: Volume control)

    Do you believe there's going to be any unwanted perceived noise?

    In this case the effect of the wiper's update should be manageable (small steps) because the resistor's voltage variation is continuous, but I imagine there d be some interaction with the I2C activity. 

    Is there any best practice I can follow?

    thanks

    G.