No, I wasn't using my own cable, just the cable that in each case the girl handed to me. but I noticed that at each open -mike session, at least one other acoustic guitar (and perhaps all of the guitars!) had a slider on the body side, indicating a battery-powered pre-amp. Now this means those guitars will be producing a higher output signal than my own passive pickups. Most of my guitarist friends who gig independently have guitars with battery-powered pickups but I never had problems with my passive pickups in the past.
Maybe I'm being naive to think one can just go plug into a mixing board type console (sorry, I don't know the technical term for this) and play. On the two sessions I went to, there was no advice "bring your own amp" or even "bring your own pre-amp if there isn't one on the guitar". I realise that open-mike sessions are very popular these days, taking place at venues all over the country and I suppose not many will have the Peavey type PA that we use in my band, as they're more cumbersome.
Unfortunately I didn't note any details of the equipment used at those two sessions, just suffered the annoyance of waiting in front of an eager audience while the operator faffed around and then said lamely "is your pickup working?"
So was it me, or the consoles?