Zipper noise When Adjusting SQ Preamps

[airickess]

I work at a large entertainment complex in Los Angeles. The company has at least 8 SQ consoles of various frame size complex-wide. We have had a persistent issue with digital zipper noise being audible in every SQ when adjusting the preamp pot. This issue turns up regardless of firmware version. We have tested it on consoles using FW 1.5.9, 1.5.4 and 1.4.4 and the noise still happens.
When we connect any of our DX168 boxes to any of the SQs, switch a channels input patch from Local Input to SLink Input and move the preamp up and down the sound is much worse initially. Then after moving the preamp encoder up and down a few times the noise lessens to the same audible level that the Local Inputs make while moving the preamp encoder.
I do have one fader on one SQ5 console that is silent when patched to Local inputs – all the rest have that zipper noise. This same single fader does make the loud zipper noise when assigned to an SLink Input channel, and then it also gets quieter when the encoder is moved a few times.
Has anyone else here experienced this issue? If so, have you found a solution?

[Tobi]

I only have one SQ, but never experienced anything Like you described…

Maybe contact Support?

Best Regards,
Tobias

[Nicola A&H]

Please see Keith’s response in this thread: https://community.allen-heath.com/forums/topic/noise-at-all-local-inputs

[Rafael A&H]

Hello @airickess

‘Zipper noise’ is exhibited by all digitally controlled preamps and we use zero crossing detection to minimise this in our design.
Please note that testing unterminated preamps or preamps with no signal present affects the performance of the zero crossing detection which can result in higher levels of zipper noise.
Removing the preamp from the circuit entirely, by setting gain to 0dB, can also result in excess noise when preamp stages are re-connected (when gain is next applied).
Hence the preamp gain starting by default at +28dBs

Without the 0dB characteristic (i.e. not starting from 0dB) and when loaded/connected, you shouldn’t see anything over -30dB on the preamp meter.

If you do or if you wish to follow this up further, please contact support at Support@allen-heath.com and we’ll be happy to have a look into it.
Thank you,
Rafael

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