Weird and unwanted 80hz hum???

[mazz]

Still sounds like induced noise to me! Did you try changing the order things are mounted in the rack? For instance: does the Vintech hum if it's on the bottom? Maybe try setting the Vintech on top of the rack and then setting the other units on it (or it on them) one at a time to see if the buzz comes back. I bet it's one of the other units that is the culprit and this way you might find out which one it is.Good luck!Mazz

[bleuciel]

Hi Mazz,Oups!!! I din't think of that, shame on me. I've let the Vintech all the time on top of the other devices. I've tried by turning the other pre off, one by one after unploggued all their respective cables. And like I told, the other moment the buzz went off is when the other pre were all turned off. I will try, with changing the order.Thanks,Jean Custeau

[milfus]

is the 4th channel a balanced to unbalanced connection? cause that can dump your ground into the line too, if it is inducing noise, another option without moving, is to loop a copper wire to your case screws (loosen a bit, loop, tighten down) and run it to your rails or ground, cause then your ground loop turns into a universal ground like a studio set up, tho electrical grounds for ac are usually 55hz, but in theory if another device is inducing it, the universal ground should give a path of even less resistance (copper conducts better than air) and it could pull your spill out of the way anyhow. Iunno just a few ideas

[mazz]

Quote:is the 4th channel a balanced to unbalanced connection? cause that can dump your ground into the line too, if it is inducing noise, another option without moving, is to loop a copper wire to your case screws (loosen a bit, loop, tighten down) and run it to your rails or ground, cause then your ground loop turns into a universal ground like a studio set up, tho electrical grounds for ac are usually 55hz, but in theory if another device is inducing it, the universal ground should give a path of even less resistance (copper conducts better than air) and it could pull your spill out of the way anyhow. Iunno just a few ideasI wouldn't recommend grounding the cases to the rails in addition to the already existing chassis ground in each device. You're opening up more "ground" reference points that may not be actually referenced to earth ground, which could cause more problems.The induced noise we're discussing here is electromagentic noise created by a transformer in a power supply, either an internal power supply or a wall wart/line lump adapter (which is a transformer, basically). Grounding won't do much for this kind of noise because it is not necessarily transmitted via wiring. Physical proximity can cause this kind of noise.Grounding is a big misunderstood topic that can affect any and all electrical circuitry. I think what you are referring to is a star ground system where all outlets have their own ground wire which terminates at a common ground point, typically a copper rod that is actually in the ground. Then, every piece of equipment (assuming it's made properly) that's plugged in is theoretically referenced to the same ground point. Ground loops occur because one or more pieces of equipment are "floating" or in other words, referenced to a different ground. When a properly grounded piece of equipment is connected to a "floater", a voltage difference between ground references is created which gets in to the audio pathway.I'm not sure what you mean by ground being at 55hZ. Never heard that one before.I'm not an electrician but I do have to deal with a lot of electrical circuits in my day gig so I've had some experience. I have enough experience to know that I'd hire an electrician to fix any grounding issues in my house or studio. I don't recommend messing with grounding unless you know what you're doing!!! Electricity is a matter of life or death. I choose life!!Mazz

[milfus]

Yeah, I was 2 weeks from an aa in electronics, I have personally seen it work though, because you know generally it follows the path of least resistance, but you are right, its mainly been vintage equiptment, and I was referencing a star ground system. although I have seen EMI be pulled away by a more conductive ground as well, I didnt test it or anything, but the line noise left. but yeah I didnt mean actually tamper with the grounding device, just the old case wire trick, where you run the wire from external case screw to external case screw incase you are dumping line noise, haha. thats a thought in itself tho, all the devices are off one plug right? like on the same power supply?Oh and 55hz, for ac voltage is by far the most common frequency of a ground leak for line noise, like to the point some hum reducers have a setting just for ground noise. they say 60hz but ive never seen it and if you look at x-hum, it has a setting for 55Thought I forgot somethin, yeah the copper wire to the cases and the rail also operates on the faraday cage theory, from back in the 50's radio rooms, because the conductivity would pull the radio interference and the line noise into the cage which was usually put directly into the sunken ground line. You just use the chasis and the rails to unify the ground so if there is a ground leak it will pull towards the line with the most grounding potential, but generally its used on studio racks, but either way I would rather have a controled ground leak than a wild one, because it wouldnt have too much of an effect unless there actually was a leak.Yeah on second thought running a safety ground wire might be a bit tricky, I am used to a streamlined ground, if you look I even said to attach it to the ground. and a farady cage is a focal point for a single point ground too, yeah that trick IS in one of my text books though, I am staring right at it, its in the "understanding audio" book

[bleuciel]

Hi Mazz and Milfus,Thank so much to take this time for me. My 4th channel is a balanced connection like the 3 others and the connection of my other pres are balanced too but with TRS 1/4 inch jacks in a snake of 8 cables.Jean Custeau / bleuciel@mail.com