
Originally Posted by
Deborah Crook
I've been running sound for a smallish convention over the weekend, using an X32/S16 pair as the main sound desk. We had some serious issues, though:
1. We had quite a few loud pops on the main speakers. We were recording via the XUF card to a PC, and have these captured; what we saw was multiple inputs going from zero to full scale (both positive and negative full scale observed at different times) for a single sample, and then returning to zero on the following sample. Mix bus outputs tracked this spike with a 16 sample delay, and main FoH outputs (which had a TruEQ inserted) showed the same spike with a 40 sample delay.
We believe that the hotel's mains supply may have been noisy -- our hypothesis is that there may have been some kind of inductive switching resulting in mains-borne noise -- but we're a little suspicious that this may have induced problems in the digital domain. Can you comment? For the third day of the convention, we fed the main desk via a Samson PowerBrite, and didn't have this problem beyond that point. Do you expect to need mains filtering (or online UPS) on the X32 (and / or the S16)?
2. More seriously, on three occasions the desk spontaneously switched itself off, and refused to turn back on for around half an hour. On the first, we initially identified the problem as having been a corroded power pin on a mains cable; however, we checked the whole chain of the power feed after that, and it couldn't have contributed to the second and third cases. We now believe that the first case may actually have been the same as the other two, although we can't prove one way or the other.
In the second case, the screen and all lights on the desk just turned off. Switching mains off and on did nothing; the mains cable was checked and found to be supplying 240V normally. After ten minutes switched off, turning back on still did nothing. Our best guess was a thermal shutdown; after a further fifteen minutes switched off with adjacent exterior doors open (and outside temperature around 0C) the desk restarted normally.
In the third case, we saw almost identical behaviour, except the desk shut down, started rebooting about a second later, completed the reboot sequence and activated the control surface, and then instantly shut down completely, refusing to reboot for around half an hour again. After the second occasion, we had relocated the desk to be further from heating vents, and ambient was (estimated) around 22-23C.
Has anyone else seen this kind of behaviour? We had an extremely sympathetic audience who had been warned we were trying new technology; with a normal audience, we'd have been lynched. Fortunately, given we hadn't run an event on the X32 before, I'd taken a Soundcraft Live4 analogue system (and a multicore snake) as an emergency backup. Rewiring the stage and the entire desk mid-concert definitely comes under the heading of Not Fun, though, even with a sympathetic audience. Right now, I can't consider using the desk for higher profile events, which is deeply disappointing and annoying; apart from these issues, the X32 was a near-perfect fit for this kind of use (small-medium music convention), but that's a really big "apart from".
I sent a much more detailed version of this (but without the third shutdown documented) to care@ on Saturday night; I'll follow up with the details of the last incident.