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POP free codec for ADAU1701
POP free codec for ADAU1701
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Old 29th September 2019, 03:43 PM   #1
Baldin is offline Baldin  Denmark
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Default POP free codec for ADAU1701

Have a miniDSP 2x4, and have also just bought a Sure Electronics DSP board with the same ADAU1701 dsp.

Both implementations have a bad pop when turning on or off. Looking at making my own implementation to build directly into active speakers.

You can implement a muting circuit with a fet on the output of each channels to compensate for this, but it will require quite some discrete components, so I was wondering if there are some better performing codec which could both boost performance and which has good muting circuits implemented already.
Maybe also being able to skip the opamp based filters on the output which at least the Sure output board seems to have could also be omitted.

I'm told that DACs like TI's PCM5102 has good muting circuits built in.
So that could be a way to go. but this will require to of these to get to the 4 outputs, and no improvements to the ADC.

But even better would be a one chip solution with bot better ADCs and 4 or more DACs.

What about Cirrus Logic's CS42516?

What would be a good and easy path in this?
Any experience, with different solutions and manufactures?

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Old 20th October 2019, 06:07 PM   #2
Baldin is offline Baldin  Denmark
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After doing a bit of study believe there is at least 4 ways to go about this:
1. External muting circuit using either fets or bipolar transistors like the 2SD2704
2. Using a dedicated analog switching circuit which is already made for muting circuits and which accepts negative swing. A solution could be build around FSA2276.
3. Using a line driver with build in charge pump and muting circuit. A good candidate would be TI’s DRV603
4. Using a separate DAC with build in click and pop reduction. Good candidates would be TI’s PCM5100A/ PCM5101A/ PCM5102A. A good side effect would be a better overall THD performance.

My conclusion so far is that least expensive and least complex is to use a line driver with internal pop elimination. One good choice would be the NCS2632 from On Semi. It has a little lower distortion than the DRV603.
The output filters can be implemented with the line drivers and a small TCM809 can be used for supply voltage detection.
See attached schematics (2 channels shown). VOUT1 is connected to the ADAU1701 DAC output 1 etc.
Attached Images
File Type: jpg Mute.JPG (84.5 KB, 35 views)

Last edited by Baldin; 20th October 2019 at 06:09 PM.
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Old 21st October 2019, 04:27 PM   #3
CyberPit is offline CyberPit  Japan
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Join Date: Apr 2018

One more way to mute.
Using micro relay instead of muting-Tr./FETs to short the output signals.

+ No negative power supply required.
+ A break contact can mutes even in the Power Down State.
- Increase power consumption.

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