LukeFRC Posted December 6, 2021 Share Posted December 6, 2021 Anyone got any ideas... took a Korg SV1 keyboard to church yesterday for the keys player to borrow.... plugged in BUT TURNED OFF, and connected to the desk via XLR, or jack and DI box we got some crazy high pitched squeals and whines coming through the PA it wasn't turned on... what could cause that? something getting from the earth and neutral into the audio inputs? Quote Link to comment Share on other sites More sharing options...
fretmeister Posted December 6, 2021 Share Posted December 6, 2021 Did the PA have phantom power turned on the channel the keyboard was using? Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted December 6, 2021 Author Share Posted December 6, 2021 34 minutes ago, fretmeister said: Did the PA have phantom power turned on the channel the keyboard was using? No - pretty sure we turned it off. (Ie not 100%) Quote Link to comment Share on other sites More sharing options...
jimbobothy Posted December 11, 2021 Share Posted December 11, 2021 … if it’s yours have you tried it back at home and is it working as normal? Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted December 11, 2021 Author Share Posted December 11, 2021 29 minutes ago, jimbobothy said: … if it’s yours have you tried it back at home and is it working as normal? yeah working fine at home- need to do way more testing. Quote Link to comment Share on other sites More sharing options...
AndyTravis Posted December 12, 2021 Share Posted December 12, 2021 Doesn’t the SV have a valve in it? is it in need of a service/valve replacement? Im sure it’s just a 12ax7 or something Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted December 12, 2021 Author Share Posted December 12, 2021 6 hours ago, AndyTravis said: Doesn’t the SV have a valve in it? is it in need of a service/valve replacement? Im sure it’s just a 12ax7 or something Yes - but would a faulty valve cause noise if the SV is turned off?! Quote Link to comment Share on other sites More sharing options...
jimbobothy Posted December 12, 2021 Share Posted December 12, 2021 … could it be a faulty couple if strips on the desk? If the SV is fine at home in a similar scenario could it suggest something else is at fault? Quote Link to comment Share on other sites More sharing options...
AndyTravis Posted December 12, 2021 Share Posted December 12, 2021 3 hours ago, LukeFRC said: Yes - but would a faulty valve cause noise if the SV is turned off?! If it’s cooling down? Dunno. it was late… Quote Link to comment Share on other sites More sharing options...
Owen Posted December 12, 2021 Share Posted December 12, 2021 Some pieces of kit make strange noises when connected to stuff if they are not on. Is it to do with earthing? Dunno. Quote Link to comment Share on other sites More sharing options...
BigRedX Posted December 13, 2021 Share Posted December 13, 2021 Does it still make the same noise if it is completely unplugged from the mains? Somer gear never properly switches off unless unplugged/turned off at the mains socket. Quote Link to comment Share on other sites More sharing options...
Huge Hands Posted December 13, 2021 Share Posted December 13, 2021 Was it an active DI box, or a passive one? Most active ones use phantom power to run the electronics, so if you've turned phantom off, it would be relying on the battery inside the unit, which could be on its way out and cause some weird stuff. Also, does the church have a cabled hearing loop? It could be some sort of feedback through that? Quote Link to comment Share on other sites More sharing options...
Owen Posted December 13, 2021 Share Posted December 13, 2021 Cabled hearing loops are comedy gold for unexplained feedback. Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted December 13, 2021 Author Share Posted December 13, 2021 3 hours ago, BigRedX said: Does it still make the same noise if it is completely unplugged from the mains? Somer gear never properly switches off unless unplugged/turned off at the mains socket. no, the moment it was unplugged no noise. (Which stands to reason really as there's nothing going in anywhere to go out the outputs.) 2 hours ago, Huge Hands said: Was it an active DI box, or a passive one? Most active ones use phantom power to run the electronics, so if you've turned phantom off, it would be relying on the battery inside the unit, which could be on its way out and cause some weird stuff. Also, does the church have a cabled hearing loop? It could be some sort of feedback through that? So noise was first via the balanced XLR with no DI box used. Phantom off to stop blowing up anything. Then tested one channel with Active orchid box so active. We turned phantom on for that test - same result. And we used a different power socket the other side of the room. 2 hours ago, owen said: Cabled hearing loops are comedy gold for unexplained feedback. Yeah I think it could be something like that. or all the fairy lights on the Christmas tree. Thanks for your help everyone - tbh I need to go and do some tests on things in the room and at home before wasting any more of your time and expertise. Quote Link to comment Share on other sites More sharing options...
Huge Hands Posted December 14, 2021 Share Posted December 14, 2021 11 hours ago, LukeFRC said: And we used a different power socket the other side of the room. FYI normally if you're picking up hum or weird stuff through ground planes on equipment, it is better to have everything plugged in to the same socket so they share the same ground path and avoid potential differences between them. Obviously this is not always possible in large buildings or with lots of equipment where you don't want to overload the socket, but keeping the stage equipment on the same circuit would be something to try. 1 Quote Link to comment Share on other sites More sharing options...
DanOwens Posted December 14, 2021 Share Posted December 14, 2021 I have some gear that, when off and connected to the PA, produces an almost inaudibly high whine sound. This goes off as soon as the gear is turned on, or if disconnected from a power source. I've always attributed it to earthing, or some kind of leakage of power into the audio circuit. I'm no electronician, but its consistent across a couple of pieces of gear in a couple of locations. 1 Quote Link to comment Share on other sites More sharing options...
Jean-Luc Pickguard Posted January 3, 2022 Share Posted January 3, 2022 There is a simple explanation. The demon living inside the keyboard was expressing his displeasure at being in a church. 2 Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted February 16, 2022 Author Share Posted February 16, 2022 For anyone who cares (and @Owen who will humour me) I solved it! It's fixed and works!! Test at home: plug into mini mixer with headphones, low signal lots of noise... my 3 year old daughter has the cans on.... "Hmm maybe it's something in software settings?" I think - go to plug USB cable in and BANG the signal jumps up giving my 3 year old a fright (her hearing is fine) so first problem is that something on the USB port was doing something odd... seems to be fixed. As Jean-Luc suggested asked the Demon to go elsewhere, he's now made up home in my wife's hairdryer. Will deal with this problem later. Took to church, plugged in.... it works but the XLR outputs are +4dBu and the preamp on the desk needs to be set at about 0db, maximum 6db ... so if we plugged in and it hadn't been turned right down that would explain the noise too.... Then the noise floor is pretty high, experimenting (I've not been involved with the tech at church) so some random cable extension is putting a load of noise in the signal, switch that and bingo we're ok! Still can't play the bloody thing myself but hey ho! Quote Link to comment Share on other sites More sharing options...
Owen Posted February 16, 2022 Share Posted February 16, 2022 Very dissapointing that this did not resolve itself by buying new kit. 1 Quote Link to comment Share on other sites More sharing options...
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