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[Craig Hauber]

These things have been around long enough now and they are definitely an "all your eggs in one basket" type device.
Just had a first generation Audia fail in a large college type auditorium and have several BSS omnidrives with burnt-out display backlights and failed front-panel buttons (they are still holding their settings so I don't touch them) And I have many nightclubs with Ashly protea 24.24's that don't open up until too late in an evening for me to get there in time to fix if something fails.

How do you handle this type of thing?  You just can't say screw'em when someone calls in a panic.  
Is there a method to switch to backup unit that can be semi-automated?  

What plan do you all have for handling this.

In the old days stuff would slowly start to fail or give warning signs for months -and even when something died it may have only effected a pair of speakers out of many.  When these DSP's quit it's very sudden and the entire facility goes silent.  

[Ivan Beaver]

We don't supply backup DSP's as standard-but could if the customer wanted to pay for it.

Since there is no way of telling what could go wrong, the most failsafe way is to have two identical DSP's and a switchover system consisting of relays that are in the normally closed state.

You switch all the inputs and outputs to a new DSP with a switch that engages the DSP's.

You want a complete switchover.

Simply paralleling signal paths could have a problem if the particular input or output devices fail and short the line-causing the line to be "dead"-even if a good device is hooked up to it.

[Craig Hauber]

That was one thing I was pondering.  Yes I can easily supply a second identical DSP, but how does a customer switch it over?  Moving 30 phoenix connectors probably isn't going to happen (knowing my customers!) So I was thinking of the parallel operation but with relays to remove the dead unit from the chain in case of loading issues on the lines.

Some other thoughts:

Do you leave the backup dsp on and running or fully disconnected from the mains until needed?  -saves it from mains power related failure but requires someone to plug it in.
-and yes, I've seen dsp's do really strange things due to block-wide power spikes and surges while the amps didn't seem to mind -especially in large construction areas like these new mall -almost-a-city -type of complexes I've done system installs in.

Do you run the primary dsp 24-7-365?  -I tend to.  -and to solve the problem above I've started using UPS's -just for the dsp as some analog gear doesn't like the square-wave output of most units.  But this then makes you wonder how good a UPS is since it contains lead-acid batteries.  Should they be cycled occasionally?  Do they risk bursting and causing other severe damage in a rack, what about power outages -does the UPS shut down gracefully when it's batteries die un-attended or do they brown out?  How about when power is restored? they might cause a worse spike/bounceback than not having it at all.

Relays,- what are the contact life on these things if they aren't used in a warm dry dusty rack for several years then suddenly called on to engage.  Anybody have a good signal-grade relay that they recommend?  (there's 1000's to choose from in the Mouser catalog!)

I know it's impossible to have a perfect system but when your selling an entire 2nd DSP to your client as "insurance" I would hate for the system to remain dead when the emergency plan is activated.

-And yes, I know amps could die too but they tend to be more robust and there's multiples of them that the odds against complete failure are better.  (something that would take them all out would hurt other systems in the place too such as the video rig, architectural dimmer controller or the POS system)
I also stagger channels on amps so that not one amp is doing an entire band (so if 1 dies they don't lose all the highs with only subs remaining)

Sorry for the rambling post, just putting thoughts down as they pop into my head.  I find this stuff very interesting.

[Ivan Beaver]

I would leave the 2nd DSP not exactly powered up.  Plug its AC into say a Lowell RPC 20 AC line switcher that is switched on when you switch the switch to swap the DSP's.  It will take a little bit for the DSP to power up.  If that time is not acceptable, then you will have to leave it on.

Now how the customer is going to figure out the DSP is bad and not a cable somewhere or a switch on the console is a totally different matter .

If you use sealed relays or reed switches the contacts will remain fine-but you will pay a price- literally

I have probably installed 800 or so DSP's of all types.  If you take the Behringer fying bacon issue out of the count, I think we have only had 2 or 3 DSP failures.  And those have all been discontinued models-(maybe there is a reason they are discontinued )

It all boils down to how much redundancy you want.  There are all kinds of other places that can go bad also-what about your console for example?

[Chad Johnson]

I've never spec'd a redundant DSP system.

I suggest using units with no displays for starters, but that's not always practical. Unless the job or client requires it, I always spec the same brand.

Coincidentally I had a DSP fail in April. I was able to run one of my own over and drop it in and load the files without a hitch.

I always have one of those DSP units in my own rack and I always keep the system files on disc in a file as well as on my programming tablet. Its not hard for me to pop in a replacement unit and load the files in very short notice.

[Brad Weber]

Craig Hauber wrote on Sat, 05 September 2009 15:16

Do you run the primary dsp 24-7-365?  -I tend to.  -and to solve the problem above I've started using UPS's -just for the dsp as some analog gear doesn't like the square-wave output of most units.  But this then makes you wonder how good a UPS is since it contains lead-acid batteries.  Should they be cycled occasionally?  Do they risk bursting and causing other severe damage in a rack, what about power outages -does the UPS shut down gracefully when it's batteries die un-attended or do they brown out?  How about when power is restored? they might cause a worse spike/bounceback than not having it at all.

I typically use online, sine wave output UPS units in front of SurgeX devices for the DSPs, network switches, etc. in a system.  If there is a control system, the UPS is tied into that via serial or network communication so that an orderly shutdown can be initiated if the UPS runs down too much.  By putting the UPS first it does put that at risk during a surge but you can shut down the system via the SurgeX and still be fully protected.

[Don Boone]

Brad is there a reason for putting the UPS upstream of the SurgeX?
Seems like the SurgeX should come first.

Don

[Ivan Beaver]

Don Boone wrote on Mon, 07 September 2009 15:44

Brad is there a reason for putting the UPS upstream of the SurgeX? Seems like the SurgeX should come first. Don

Actually there should be a SurgeX before and after the UPS.

Having it after would "catch" something if the UPS went belly up and did weird stuff.

[Craig Hauber]

I've searched around and they are either really expensive (more than the DSP itself) or really huge (or both)  Any recommendations on brands and models?  
I'm looking for something to keep a DSP afloat long enough to weather on/off surges, spikes and brownouts -not endless uptime (450 to 700VA square-wave units give me enough time but don't like the relay bypass on-offline and as mentioned earlier really despise the square-wave action.
I also would like ones that can handle the production-audio end of my business too (portable and don't complain about road-case and transit vibration)

thanks again

[Brad Weber]

Ivan's right that before and after would be ideal and if it is simply an inline surge suppressor and a UPS that are always live then it would make sense to put the surge suppressor first.  However, locating a sequencer or any switched power device before the UPS does not usually work well.  For example, you might want to put a media server, digital mixer, DSP and some external effects devices on a UPS, but want to sequence those on and off.  Or you may want the control system and system DSP off the UPS but with the control system always on and the DSP being switched on and off.  You can't easily do either of those with the UPS after the sequencer or switched power as not only would that require multiple UPS devices, one per sequenced circuit, but when a circuit turn off it would also cause the UPS to engage and run the equipment off the battery until the battery drained rather than turning the equipment off.  Adding to this, now the battery is drained and the next time you turn on the system you have to hope you have no problems until it had sufficiently charged.