GX4816 / Avantis – intermittent digital crackling / popping noise – possible clock/sync issue? Has anyone experienced this?

Avantis Avantis Feature Suggestions
1

Hi everyone,

I would like to ask if anyone has experienced the following problem with an Allen & Heath Avantis + GX4816 system.

I’ll try to describe everything in as much detail as possible, because to my ears the problem sounded very much like a digital clock / sample alignment / audio sync issue, but I don’t want to assume that this is definitely the cause.

System:

  • Allen & Heath Avantis Solo

  • GX4816 stagebox

  • GX4816 DX1 → DX168

  • PA currently fed from the analogue LR outputs of the GX4816

  • Avantis Audio Clock Source: Internal 96 kHz

  • no second console in the system

  • GX4816 connected directly to the Avantis – no network switch or other network device in between

The problem

During a rehearsal / system operation, a very strange popping, crackling, static-like digital noise suddenly appeared.

The interesting part was:

  • it was only audible when a channel actually had audio signal;

  • increasing the channel level also increased the noise;

  • it did not sound like normal analogue hum or ground-loop noise;

  • to my ears, it sounded almost exactly like the kind of digital popping you hear when two digital consoles / a gigaACE system are not correctly clock-synchronised.

However, there was no second console in this system.

What I tested

I first checked the GX inputs.

Then I tested an Avantis LOCAL input, and the exact same type of crackling/popping noise was present there as well.

This made the situation more interesting, because it didn’t seem to be simply a problem with one GX analogue input.

I also tested the output side:

  • initially some outputs were patched through the DX168;

  • I then repatched the outputs to the GX4816 analogue outputs;

  • the problem remained.

So it did not appear to be limited to one particular DX168 output or one specific GX input.

Cable tests

I also checked the CAT cable.

At the time of the problem, I was using a relatively short 3 m cable.

I replaced it with another cable, but the crackling did not disappear.

Eventually I rebooted the GX4816.

Immediately after rebooting the GX4816, the problem disappeared.

I also checked the Avantis History / Event Log, but there was nothing obvious that explained the problem.

The Avantis is currently running firmware V2.00.

One interesting previous incident

I had a different but somewhat related problem with this system previously.

In that case I had a red flashing error indication around the GX Connect/Link, and there was a very long CAT cable involved.

Replacing that cable fixed the problem.

The current incident was different:

  • short ~3 m cable;

  • apparently normal link;

  • no visible red error indication;

  • Audio Sync Lock appeared normal;

  • changing the cable did not solve the problem;

  • rebooting the GX4816 did solve it.

I am currently running a 10 m cable, and since rebooting the GX4816 the system has been working normally.

Another important detail

I have experienced a similar type of problem with another Avantis console and also with an SQ console, which makes me less inclined to suspect the particular Avantis Solo itself.

This is why I am starting to wonder about the GX4816 / SLink / GX audio stream / clock synchronisation side of the system.

But I don’t want to blame the GX4816 without evidence.

What I would really like to know

Has anyone experienced a GX4816 problem where:

  • the connection appears to be normal;

  • there is no obvious Link/Connect error;

  • Audio Sync Lock appears normal;

  • but a digital popping/crackling noise appears;

  • the noise is present on channels carrying audio;

  • the noise increases with channel level;

  • changing the CAT cable does not solve it;

  • but a complete GX4816 reboot immediately fixes it?

Could this be caused by an internal clock/sync/audio-interface state, GX port/PHY issue, power supply issue, thermal issue, or some kind of firmware/software state?

And perhaps most importantly:

Can replacing/reconnecting the CAT cable fail to clear a latched digital/audio-sync state, while a complete GX4816 power cycle resets it?

I am trying to understand this before taking the system into a live concert situation. I really don’t want to discover the actual cause during a show. :slightly_smiling_face:

If anyone has experienced this exact kind of clock-sync-like digital crackling/popping with a GX4816 + Avantis/SQ system, I would really appreciate hearing what the eventual cause was and what fixed it.

Thanks in advance! :folded_hands: