Members Dark Ice Posted March 6, 2007 Members Share Posted March 6, 2007 Alright, I know its a long shot that anyone can diagnose this over the internet but its worth a try, at least. In our church system, every so often theres a random event that occurs, in that the volume will decrease and the noise floor will get louder (you hear the hiss increase), and eventually the opposite will occur where the hiss dissapears and the volume increases (usually with a bit of feedback because the system was installed by a hack and its not very stable). Id guestimate maybe a 3-6dB difference. The system is not used for music, only for vocal amplification, all wireless microphones, some TOA VHF, some Sennheiser UHF. The problem isn't unique to one channel or one type of wireless system, so I dont believe the fault lies there. The rest of the system consists of a peavey RQ2310 mixer, Peavey CEQ280a digital EQ, Bose panarray system controller (must be a predecessor to this one, a Peavey PV2800 amp, oh, and bose speakers... :/ The problem is totally random, I couldn't reproduce the fault on demand, the system could be totally stable for half an hour before it happens. I know its a long shot but...any ideas folks? Steve. Link to comment Share on other sites More sharing options...
Members agedhorse Posted March 6, 2007 Members Share Posted March 6, 2007 My first guess isnthat it has something to do with a balanced line becoming unbalanced, which will change the overall gain by 6dB. A bad (intermittent) cable is my first guess, and it could be anywhere that a balanced interconnect is used. A second guess is that a differential line driver (balanced output amp) is bad (one of the 2 line drivers) most of the time, but will occasionally function correctly (gaining 6dB) . Link to comment Share on other sites More sharing options...
Members ashivraj Posted March 6, 2007 Members Share Posted March 6, 2007 I know you've said it's NOT the wireless, but it sounds like the wireless - we've had a similar-sounding problem with our (cheap) VHF stuff. Every now and then, ssssss (getting louder) and then ssssT and it goes back to normal. AS Link to comment Share on other sites More sharing options...
Members bassred Posted March 6, 2007 Members Share Posted March 6, 2007 My guess would be the RF first. But if it is in fact the board (or rig) agedhorse nailed it on the head. Link to comment Share on other sites More sharing options...
Members agedhorse Posted March 6, 2007 Members Share Posted March 6, 2007 I'm assuming everything is increasing, which is what's causing the system to go into feedback. It's like turning ALL inputs up by about 6dB. Link to comment Share on other sites More sharing options...
Members SoundMan Posted March 6, 2007 Members Share Posted March 6, 2007 First chance you get, pull the lid off of that CEQ280 and check the condition of the backup battery. We had some cases of those going bad, and leaking on to the circuit boards. The CEQ has an internal gain calibration, and well, that unit is all about level manipulation anyway. So, mix in a leaky battery into the control circuit, and you might end up with a funky level situation. SoundMan Link to comment Share on other sites More sharing options...
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