Gswitz Posted July 30, 2019 Share Posted July 30, 2019 (edited) I have a hum and I'm struggling to run it down. My devices are... RME UCX RME Quad Mic Pre Audient ASP 880 RNeve 5211 DBX 162 (I get the hum when it's completely removed. Currently, it's wired in to the patch-bay and unplugged.) All my stuff is wired through a patch bay which makes this trickier. It's most apparent on the Neve. This has a ground lift. The ground lift doesn't solve or impact the problem noticeably. With only the RME plugged in or with everything plugged in, RME channels 1,2,3,4 have no hum. I wire the RNeve output to channel one on the RME and turn it on and I can see the hum. I try lifting the ground on the Neve and I still have hum (there's a switch on the back). There was no noticeable change. I try one of those 3 prongs to 2 prongs for the Neve and I still have the hum. With the Neve unplugged, only the RME and Audient plugged in, I crank the gain on the Audient channels and see a little hum. It is less than the hum from the Neve but less gain too. I can do the same on the RME Quad Mic Pre, but it is less than the hum from the Audient almost not noticeable on the spectral analyzer. Pulling everything apart to trouble shoot this is going to blow. Any direction to efficiently find the problem is welcomed. Honestly, I've never had noticeable hum before. I caught it recording the ribbons with tons of gain a couple of weeks back. I wouldn't say the hum is loud, but who wants hum? I usually have everything plugged in to the same power strip but I tried separating the plugs and saw no improvement. I think my next step is to isolate the Neve and the RME so that they are only plugged in to each other and see if I get any hum. Totally pia to unplug everything, but it seems like my only path forward. I guess unplugging is easy. 🙂 Wiring it back up is going to be a herculean task. I tried running the output of the Neve to input 1 on the RME UCX without going through the patch-bay. This did not help. Edited July 30, 2019 by Gswitz Link to comment Share on other sites More sharing options...
Jesse Screed Posted July 30, 2019 Share Posted July 30, 2019 I wish I could help, but maybe the bump will catch the attention of a geek or two. But since this is the CH, you might get a lot of this 1. That happened to me once. I had a faulty ....... 2. That happened to me once. I tried everything and then one day it just went away. 3. Sucks to be you. Unplugging everything will be a total pain, but it might be the only way to trouble shoot completely. Link to comment Share on other sites More sharing options...
Zargg Posted July 30, 2019 Share Posted July 30, 2019 Hi. Does it matter where in the patch bay things are connected? Just in case it could be the patch bay itself. As mentioned above, hope someone with proper knowledge can come and aid you. All the best. 1 Link to comment Share on other sites More sharing options...
Gswitz Posted July 30, 2019 Author Share Posted July 30, 2019 It'll be a learning experience. I'll take an afternoon and run it down. More to come. Link to comment Share on other sites More sharing options...
msmcleod Posted July 30, 2019 Share Posted July 30, 2019 I can't think of any alternative to unplugging everything and plugging it back in. Before you do that, check your earth connections in any 3 prong plugs. Something could have come loose. Also, check audio cables for dry joints on the earth. I had a nightmare earth loop that went away when I unplugged everything, but came back once everything was back in their rack cases... The mixer & effects were in one rack, and the power amp in another. It turned out the earth loop was through the rack casing itself. Putting some insulating tape around the rim of the case solved it. 1 Link to comment Share on other sites More sharing options...
Jim Roseberry Posted July 30, 2019 Share Posted July 30, 2019 Is everything powered from a single outlet? If not, I'd try that before unplugging all audio. Link to comment Share on other sites More sharing options...
Gswitz Posted July 30, 2019 Author Share Posted July 30, 2019 Yes, everything is powered from a single outlet. Link to comment Share on other sites More sharing options...
Gswitz Posted July 30, 2019 Author Share Posted July 30, 2019 9 hours ago, Zargg said: Hi. Does it matter where in the patch bay things are connected? Zargg, this was an awesome hint!! (also I think the problem is correctly diagnosed). So, I have a 25' snake that has 6 XLR inputs and I plug 2 into the RN 5211 and 4 into the Audient. The problem comes if I cross the streams. (of course!!) Everything plugged into the Audient must only go to the Audient and everything going in to the RME must only go into the RME. The Snake merges all the audient inputs with items I was then routing into the RME. I obviously thought all the inputs in the snake were isolated. Whoops. 🙂 So, if I have things plugged into the snake going into the Audient and the RN 5211 and then I route the output of the 5211 into the RME, I have made the loop! 🙂 If 2 of the Snake channels are for the 5211 and 4 are for the Audient, I have to plug the 5211 into the Audient inputs. If 2 of the Snake channels are for the 5211 and 4 are for the Quad Mic Pre, I have to plug the 5211 into the RME Analog Inputs (1-8). This fixes my problem. Does this mean my Snake is bad? Link to comment Share on other sites More sharing options...
Gswitz Posted July 31, 2019 Author Share Posted July 31, 2019 Ok.... I thought i had it, but i don't. Next step is remove the patch bay. Link to comment Share on other sites More sharing options...
Gswitz Posted August 2, 2019 Author Share Posted August 2, 2019 (edited) Here's what... When you have a mic cable unplugged from a mic but plugged in to the interface and crank the gain up you can see a little hum. I don't think this is a problem. It goes away when I plug in the mic. But the recording I made on 6/30/2019 definitely had hum on my quietest ribbon. Here's the thing... it wasn't constant. It comes and goes. It is more faintly apparent on the other mics. http://gswitz.blob.core.windows.net/tunes/20190630_ChrisVasi_xx_hum1.wav http://gswitz.blob.core.windows.net/tunes/20190630_ChrisVasi_xx_nohum1.wav So, either as I adjusted and moved mics the hum showed up or there was some power supply issue in the house. Maybe it was the AC Unit? It was present for most of the recording. I can't actually find a problem in the rack of gear. One thought I had, it's probably a good idea not to leave the snake plugged in to channels you aren't using. Yes? No? It's a nice convenience, but I'm not sure it might introduce unnecessary risk. Is this stupid? Is it fine to leave it plugged in? This is the mix of the recording. http://gswitz.blob.core.windows.net/tunes/20190630_ChrisVasi.html The ribbon it was hardly apparent on had a shock mount and the ribbon it was loud on did not have a shock mount -- it was screwed into the mic stand that was firmly on the floor (probably hard wood with a thin rug but I'm not sure now). Edited August 3, 2019 by Gswitz Link to comment Share on other sites More sharing options...
Jesse Screed Posted August 3, 2019 Share Posted August 3, 2019 head scratcher for sure like a reality show do not pull out any more hair but keep trying to figure it out you'll figure it out and I can't wait to hear what it is. Link to comment Share on other sites More sharing options...
PhonoBrainer Posted August 3, 2019 Share Posted August 3, 2019 (edited) The key might be its intermittancy. On that same electric line in your house, is there a fridge or fluorescent? Has any new appliance been introduced to the home recently? How close are you to your neighbors? If you listen very close to the hum, is it a commercial radio signal? Does any of your equip have tubes? Have you taken pieces of equipment out of situ and plugged them in somewhere else? You prolly done thunk of these already. . . Edited August 3, 2019 by emeraldsoul Link to comment Share on other sites More sharing options...
Gswitz Posted August 3, 2019 Author Share Posted August 3, 2019 (edited) The recording with the hum was not made at my house. I took my gear out to record it. At my house i can't actually recreate it. I think the problem was the hvac system in the house. Edited August 3, 2019 by Gswitz Link to comment Share on other sites More sharing options...
craigb Posted August 3, 2019 Share Posted August 3, 2019 I used to have a hum issue in the first bedroom I tried putting a studio in (previous house I had). I bought one of these and still have it! Turned out, the previous owners (who built the house) had cut many corners and most of the house wasn't even grounded! When that and all the other code issues were finally fixed, I was out over $91k(!) but the hum issue was gone. After that, every one of my many racks all had a Furman Power Conditioner in one of the rack spaces. Another thing I carried with me whenever I played out or did "roadie" duties is one of these: A few people would still be alive if they had checked the outlets before connecting their gear! 1 Link to comment Share on other sites More sharing options...
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