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Dante Avio on an Oscope, What am I missing here?

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Ed Hall:
I'm playing around with an oscilloscope and hooked it up to  Dante Avio Output module. Connected to pins 1 & 3.  I set it to output a bass guitar to look at the output signal. I've done similar with an analog signal chain and received a trace similar to what I expected.

When connected to the Avio I get the below trace that is static with no output, nothing assigned to the Avio. Once the bass was assigned I still had the same trace but it vibrated in time with the bass. The peaks are only 2.82uS apart for a frequency of 354kHz. The entire waveform vibrated, not the signal. After playing with it for about 20+ minutes, I'm lost.. What am I seeing or doing wrong?

Link to short video clip with audio.

Dante Audio Video Clip

Mac Kerr:

--- Quote from: Ed Hall on February 15, 2022, 12:23:18 PM ---I'm playing around with an oscilloscope and hooked it up to  Dante Avio Output module. Connected to pins 1 & 3.  I set it to output a bass guitar to look at the output signal. I've done similar with an analog signal chain and received a trace similar to what I expected.

When connected to the Avio I get the below trace that is static with no output, nothing assigned to the Avio. Once the bass was assigned I still had the same trace but it vibrated in time with the bass. The peaks are only 2.82uS apart for a frequency of 354kHz. The entire waveform vibrated, not the signal. After playing with it for about 20+ minutes, I'm lost.. What am I seeing or doing wrong?[/url]

--- End quote ---

What did it look like when you tried pins 1 and 2, or 2 and 3?

Mac

Russell Ault:

--- Quote from: Ed Hall on February 15, 2022, 12:23:18 PM ---I'm playing around with an oscilloscope and hooked it up to  Dante Avio Output module. Connected to pins 1 & 3.  I set it to output a bass guitar to look at the output signal. I've done similar with an analog signal chain and received a trace similar to what I expected.

When connected to the Avio I get the below trace that is static with no output, nothing assigned to the Avio. Once the bass was assigned I still had the same trace but it vibrated in time with the bass. The peaks are only 2.82uS apart for a frequency of 354kHz. The entire waveform vibrated, not the signal. After playing with it for about 20+ minutes, I'm lost.. What am I seeing or doing wrong?

Link to short video clip with audio.

Dante Audio Video Clip

--- End quote ---

Is it possible the Avio output is impedance-balanced (and a little noisy)?

-Russ

Ed Hall:
Well, I finally had some time to play with this again. One thing I found was I was looking at far too short a time period. I zoomed out and saw a waveform like I was expecting. Still not sure what's happening at 355 kHz but I don't think its something I need to worry about.

Chris Grimshaw:
I came up against something similar when I put a scope on the outputs of class D amplifiers. Plenty of HF switching mush.

Easy enough to fix, though - 2x small caps and a couple of resistors to form a 2nd-order lowpass filter. Think I aimed mine at 30kHz, and spaced the resistors to be 10x apart from each other, but still small enough that the voltage drop will be minimal compared to the scope's 1Meg input.

You might also find that simply connecting the Avio output to something with a sensible input impedance will pull the HF switching rubbish down.

Chris

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