analogRead and audio

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zip_lock

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Hello,

I have a project where I am detecting the ticking of a watch. It goes like this.
Watch -> piezo -> preamp -> EQ -> compressor -> board with teensy -> mixer -> headphones

After the compressor the audio goes to a pcb with a teensy 3.1. The goal is to detect the ticking and if the ticking stops, rewind the watch via a servo. But we dont want to hear the servo. So a relay interrupts the audio signal, this is why the board with the teensy is in the middle of the chain.

To clarify, on the board with the teensy, the audio input is connected to analog pin 4 and the normally open relay, which connects it to the output towards the mixer.

The problem is that analog read seems to inject a little tic every time the function is called. At a high frequency it creates a high pitch noise.
effectively it looks like:
compressor
|
|
|--------- Teensy A4
|
|
mixer
(of course grounded)

Anyone has any knowledge to share about this?

Also shout out to PJRC from making something really nice.
 
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use separate buffered signal for feeding pin A4 (or use a opamp buffer for it), and the line with relais goes straight to mixer.
The ADC sucks a little current by every measurement (this is normal), so that is what you hear.
 
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