Jakester Posted February 5, 2023 Share Posted February 5, 2023 So, I was fully prepared to come on BC today and rant about how I had reached my wits' end with Mark Bass stuff, problem after problem etc. Yesterday I had a rehearsal with an orchestra I play with. I play both electric and DB (sometimes in the same tune!!) and also occasionally need effects, so I have a fairly complicated setup. The rehearsal was at the same venue we always play, using my usual set up, but this time I was experiencing a really loud humming. I tried adjusting the EQ, but even with everything muted, or just going bass direct into the amp (i.e. with no effects in line at all) it was still doing it. I tried plugging the amp into a different socket, but had the same issue. We'd played in there for years without any issues, but the only difference being we'd set up in a different layout, so I was in a different part of the hall. After endless problems with the CMD121P cutting out, having been sent to Real Electronics, them charging me £160 and the problem coming straight back, I ended up dropping an LM3 head in instead. I'd assumed this had finally given up and developed yet another problem, so I was about to post seeking alternatives to MB gear. However, it seems I owe it an apology - I tried it at home and it's almost entirely silent - no humming at all. All I can think is that it was dodgy wiring on that part of the hall and even though I tried a different socket, it was on the same circuit. The one I usually use is the other side of the hall, so I'm assuming it's on a different circuit. Anyway, I'm aware you can get rack mount power conditioners, but I was wondering if it's possible to get something like a single socket thingy that would do the same job - like those RCD or surge protectors you can get? Something that I could plug into the mains end of things at different venues? A vid of the noise (ignore the rest of the orchestra running through parts!): IMG_2834.mov Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 5, 2023 Share Posted February 5, 2023 Power conditioners don't do much, if anything. The best method of power conditioning is to rectify the AC to DC, then remove any ripple with filtering capacitors. The thing is that's what your amp power supply does. Besides, noise isn't necessarily on the AC line. It might be airborne RFI or EMI. You mention having a complicated set up. That could be introducing ground loop noise. First things first, run the amp with nothing plugged in. If there's no noise that rules out the AC mains. Then just the bass. If there's no noise that rules out RFI and EMI. Then add the effects. If noise results it's probably a ground loop. There's also the possibility of a bad ground on the AC mains. It's a good idea to carry a plug in mains tester to be sure it's not dodgy. 4 Quote Link to comment Share on other sites More sharing options...
Jakester Posted February 5, 2023 Author Share Posted February 5, 2023 15 minutes ago, Bill Fitzmaurice said: Power conditioners don't do much, if anything. The best method of power conditioning is to rectify the AC to DC, then remove any ripple with filtering capacitors. The thing is that's what your amp power supply does. Besides, noise isn't necessarily on the AC line. It might be airborne RFI or EMI. You mention having a complicated set up. That could be introducing ground loop noise. First things first, run the amp with nothing plugged in. If there's no noise that rules out the AC mains. Then just the bass. If there's no noise that rules out RFI and EMI. Then add the effects. If noise results it's probably a ground loop. There's also the possibility of a bad ground on the AC mains. It's a good idea to carry a plug in mains tester to be sure it's not dodgy. Thanks Bill, but I already did all of that - the noise was coming from the amp with nothing plugged in, hence my question. 1 Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 5, 2023 Share Posted February 5, 2023 The leads me to believe a bad ground on the mains, or massive interference from either florescent lighting ballasts or refrigeration compressors. 2 Quote Link to comment Share on other sites More sharing options...
Mottlefeeder Posted February 5, 2023 Share Posted February 5, 2023 If it was a public space, it might have a hearing loop installed, which could be feeding magnetically to your bass's pick-ups. That could give you anything from hum through distortion to feedback. David 3 Quote Link to comment Share on other sites More sharing options...
DGBass Posted February 5, 2023 Share Posted February 5, 2023 I always use one of these. First rulle of plugging in anything at a gig. There was a time when I gigged big valve amps that I carried a calibrated earth loop impedance tester with me just to be super safe that I had a decent ground. It was a bit overkill but gave peace of mind. Most venues I play these days are pubs and clubs where they usually have to have electrical certificates of compliance for insurance purposes and wiring generally is very good. The little orange plug though is still peace of mind and if the supply is good and the ground checks out, I'm happy and haven't yet had any ground hum or interference issues coming out my speaker. My rack unit also has a slightly more sophisticated anti surge facility as well as a ground and supply check. I suppose next time you are at that same hall, ask to go back to your previous position and outlet to see if the hum is gone. If so its almost certain the other wiring where you got the hum is suspect. 4 Quote Link to comment Share on other sites More sharing options...
fleabag Posted February 5, 2023 Share Posted February 5, 2023 Likewise Peace of mind takes seconds. I also carry a cable tester. 4 Quote Link to comment Share on other sites More sharing options...
Jakester Posted February 6, 2023 Author Share Posted February 6, 2023 14 hours ago, DGBass said: If so its almost certain the other wiring where you got the hum is suspect I would hope not - it was a primary school hall! Sounds like that must be it though. 14 hours ago, Mottlefeeder said: If it was a public space, it might have a hearing loop installed, which could be feeding magnetically to your bass's pick-ups. That could give you anything from hum through distortion to feedback. David Hmm, could be, but if so I would have expected an issue like that to have occurred earlier in the same space (we’ve been using it for 4+ years with no noticeable issues). 1 Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 6, 2023 Share Posted February 6, 2023 If it was good before and isn't now something's been changed. Find out what and you'll probably solve the mystery. 1 Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 7, 2023 Share Posted February 7, 2023 On 06/02/2023 at 06:50, Mottlefeeder said: If it was a public space, it might have a hearing loop installed, which could be feeding magnetically to your bass's pick-ups. That could give you anything from hum through distortion to feedback. David That's useful general advice but it was howling with nothing at all plugged in. Quote Link to comment Share on other sites More sharing options...
Jakester Posted February 7, 2023 Author Share Posted February 7, 2023 Well, we're back there at the end of the month so will check again and see. If it does it again in that location in the hall, I may need to invest in a VERY long extension to reach the sockets over the other side of the hall! Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 7, 2023 Share Posted February 7, 2023 2 minutes ago, Jakester said: Well, we're back there at the end of the month so will check again and see. If it does it again in that location in the hall, I may need to invest in a VERY long extension to reach the sockets over the other side of the hall! That could make things worse. Ground loop noise intensity is increased as the length of the ground wire is increased. Worse, it varies by the square of the wire length. Doubling the wire increases noise by a factor of four. Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 7, 2023 Share Posted February 7, 2023 Surely the thing to do is head to the hall when something else is getting set up, make yourself known to the stage manager, and quickly check the power at the duff spot with the socket tester you're about to buy? 1 Quote Link to comment Share on other sites More sharing options...
Jakester Posted February 8, 2023 Author Share Posted February 8, 2023 11 hours ago, Downunderwonder said: Surely the thing to do is head to the hall when something else is getting set up, make yourself known to the stage manager, and quickly check the power at the duff spot with the socket tester you're about to buy? In a primary school? I think that's a good way to have an unwanted visit from Mr Plod! Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 8, 2023 Share Posted February 8, 2023 10 hours ago, Jakester said: In a primary school? I think that's a good way to have an unwanted visit from Mr Plod! I didn't catch that. Shouldn't be hard to phone the Principal and explain the situation. You have a horrible noise and the only difference is the other side of the stage. There is a strong possibility the power is wired incorrectly and could be hazardous. You will test it with the socket tester but would like to do that before the next rehearsal. Any chance of meeting them before school starts, it will only take 5 minutes? No chance the school cafeteria fridge is on the other side of the wall doing a bit of budget redistribution? Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted February 8, 2023 Share Posted February 8, 2023 Fridge is a sore subject in my home. One of ours died and left us with a pile of food to cook or give away! Replacement arrives sometime on Saturday the 11th. Bah Humbug!! Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 8, 2023 Share Posted February 8, 2023 I'd think it's cold enough there to put much of it outside. Not frozen, of course, although I could have done that last week. Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted February 9, 2023 Share Posted February 9, 2023 We're above freezing at the moment. Unusually warm in fact! LOL Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted February 9, 2023 Share Posted February 9, 2023 Yes, but refrigerators tend to be between 38 and 40F, so as not to freeze anything. My mother told me when I was a baby our refrigerator, in winter anyway, was a peach basket perched on a stand outside the kitchen window. It's going to hit 50F here tomorrow, then back down to the 20s on Sunday. We're usually around 10 degrees higher than Toronto, 10 degrees lower than Boston. For sure OP keep an eye out for refrigeration. Commercial units are notorious for creating a mess of the AC, even when on different branch lines. Quote Link to comment Share on other sites More sharing options...
Woodwind Posted February 11, 2023 Share Posted February 11, 2023 On 05/02/2023 at 18:01, DGBass said: I always use one of these. First rulle of plugging in anything at a gig. There was a time when I gigged big valve amps that I carried a calibrated earth loop impedance tester with me just to be super safe that I had a decent ground. It was a bit overkill but gave peace of mind. Most venues I play these days are pubs and clubs where they usually have to have electrical certificates of compliance for insurance purposes and wiring generally is very good. The little orange plug though is still peace of mind and if the supply is good and the ground checks out, I'm happy and haven't yet had any ground hum or interference issues coming out my speaker. My rack unit also has a slightly more sophisticated anti surge facility as well as a ground and supply check. I suppose next time you are at that same hall, ask to go back to your previous position and outlet to see if the hum is gone. If so its almost certain the other wiring where you got the hum is suspect. Where did you buy this DGBass? Looks really neat Quote Link to comment Share on other sites More sharing options...
DGBass Posted February 11, 2023 Share Posted February 11, 2023 22 minutes ago, Woodwind said: Where did you buy this DGBass? Looks really neat sent a pm with details. Hope that helps. 1 Quote Link to comment Share on other sites More sharing options...
Woodwind Posted February 11, 2023 Share Posted February 11, 2023 2 hours ago, DGBass said: sent a pm with details. Hope that helps. cheers!!! Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted February 26, 2023 Share Posted February 26, 2023 Is there an update? Did you get the problem sorted? Quote Link to comment Share on other sites More sharing options...
Jakester Posted February 27, 2023 Author Share Posted February 27, 2023 15 hours ago, BassmanPaul said: Is there an update? Did you get the problem sorted? Went back, checked with a tester - all fine, plugged in - no problems at all despite using all the same gear. Weird. Definitely no fridges or other heavy equipment nearby either. I mean... 2 Quote Link to comment Share on other sites More sharing options...
BassmanPaul Posted February 27, 2023 Share Posted February 27, 2023 Were you perchance standing too close to your amplifier? Magnetic pickups can handily react to the AC fields from an amplifiers' power supply. Quote Link to comment Share on other sites More sharing options...
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