SQ6 Noise- Loud pops and bangs on startup

[coppoParticipant]

Our SQ6 is powered on at the same time as the power amplifiers. The power amplifiers and sub have silent delayed switch on but it is only around 2-3 seconds so they are active by the time the noises happen.
Switch off is pretty quiet as the amps mute quicker than the desk shuts down – a soft pop that is all.

Approx 7-8 seconds after the SQ6 is powered up it emits 2- 3 loud pops. This seems to be just before it loads the last scene that was running.
It doesn’t appear to matter what state the desk was powered down in, we have tried muting everything, faders down etc etc. It will power up as you expect – everything that was muted and faders down comes back up in that same state but you still get 2-3 loud pops.

I have also tried sending midi commands to mute things a few seconds after power up but the thumps persist.
It also varies from SQ6 to SQ6. Our own is in for repair at the moment with a phantom power failure and the borrowed one (new) is actually significantly worse than ours was.
Both are on up to date firmware.

It is purely analogue install using existing stage boxes and multicores so there are no add on interfaces present.

Any ideas for workarounds or do you think there is a chance of a firmware fix? How do we request such a thing and get it actioned?

My last resort plan is to provide an inline mute to the power amplifiers that is either based on time delay (10 seconds on power up) or the result of a status request to the desk – a lot of work for something that appears like it may be a design flaw in the desk itself.

[Mfk0815Participant]

The only remedy I can see ist to increase the delay for powering up the amplifiers to, round about 20 seconds or more. The outputs of the SQ will pop during the electronical stabilisation, there are no output relays built into the SQ. I personally always startup any console first, wait until the boot up is finished and then I power up the amplifiers. I do this manually but it also can be done using a configurable power sequencer.

[coppoParticipant]

Thanks

I’m sort of surprised that other users haven’t run into this problem. I also use a behringer xr18 for a band and that has better control of outputs on power up and down than the Sq6 does.
The power amps are RAMSA ones but I’m fairly sure they are not user configurable but you made me think – I have a spare RAMSA so will open it up and see if I can tweak the power on delay and increase it to 15 secs or so from its current 4-5 seconds I think. I have the schematic so it looks easy enough. The thump is also transmitted to the sub but you get a dull whooomph from that as opposed to a loud click/bang from the FOH mains. Less painful on the ears.

I’m pretty resigned to having to add functionality to delay the power amp on moment. The system is used by many different folk of different skill levels and the bottom line is a key controlled ‘ON OFF switch’. An unskilled user has the key but all it will do is turn on mains and about 15 seconds later load a very cut down scene of 1 mike plus hearing loop. When he leaves, he removes the key and the mains goes off. I need to automate the de-thumping so it works on this dummy user scenario as well as a proper operator.

[tourtelotParticipant]

I don’t know if adding another box is in the cards for you but people like Furman make “power-up sequencer” boxes that will let you adjust when the amps come on.

Here is a 2-plug unit from an on-line retailer. YMMV.

https://www.bhphotovideo.com/c/product/927215-REG/furman_cn_20mp_contractor_series_miniport.html/?ap=y&ap=y&smp=y&smp=y&smpm=ba_f2_lar&lsft=BI%3A6879&gad_source=1

D.

[coppoParticipant]

Thanks – interesting but out of our price range. (Its a local parish church) I didn’t realize things like that existed.

We have a spare RAMSA amp and the startup delay is an IC device with a 10uF timing cap. Assuming I can get at that it is a simple matter to increase the delay by tacking a 22 -47 uF cap in parallel. Virtually zero cost. If that works I’ll swap the spare in and then modify the other one as well. Plan B – bit more expensive – is a inline relay with a delayed turn on time. Probably about £20 including the housing and relay.

[BrianParticipant]

The “best practices” of audio state that you turn on the amplifiers last and turn them off first. This has always been rule #1 in audio. Sure more and more devices have some sort of delay mechanism built into them, but that doesn’t mean we can act in a reckless manner. Just follow this simple rule and you will never have issues.

[coppoParticipant]

I agree but best practices are all very well with trained operators but not at all feasible otherwise – you need to force them to do the right thing!

Here we are talking about an installation that one of its use cases is an untrained user who has been given a key and told where to put it and turn. The system has to start up and shut down seamlessly and safely.
I have got around this now by modding the RAMSA (WP 1200) startup delay circuit so it now unmutes after 15 seconds approx. Was actually quite an easy mod.

[Author]

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