Going insane with hum from patchbay units NEED Your Help!

[Southsidemusic]

Will remove a few of the units in the morning and try what you suggest. Been recording all night and its like 5 am here so gonna close the door and run up to my house and sleep a while. Will try removing the humming units and report back in like 8-10 hrs

Big thank you to you all for the great tips and interest in this weirdness

See you soon and have a nice night

[Top Jimmy]

Originally Posted by Southsidemusic

Will remove a few of the units in the morning and try what you suggest. Been recording all night and its like 5 am here so gonna close the door and run up to my house and sleep a while. Will try removing the humming units and report back in like 8-10 hrs

Big thank you to you all for the great tips and interest in this weirdness

See you soon and have a nice night

I expect there won't be a hum which points to Darryl"s angle toward grounding. Sharing chassis ground is allowing an interchassis current to flow between 2 or more of the units in the rack. If for some unlikely reason it does still hum, the problem is in the patchbay likely via a common ground buss.

Having said all this, I honestly think you should reassess your methodology. Never in my life have I ever considered turning gear off and leaving it patched. Why? Because of this very issue. If gear is patched, it should be on. Therefore, if you want to turn it off, you should unpatch it. At least, that's my take on it.

Edit-
Darryl made a really good point I glossed over earlier. When a piece of gear is switched off, all bets are off when it comes to maintaining common mode rejection on both single-ended and differential connections.

[musicman691]

I know Christopher has said they had the wiring professionally done but still I'd check to see that maybe there's AC mains that might have the wiring wrong with say hot and neutral flipped or that if somehow the grounds have current on them. I have a little outlet tester that plugs into an outlet with three lights on the end and the sequence of lights tells what's up with the outlet it's plugged into.


Another possibility is the XLR cables themselves. I've encountered several over the years that are miswired from the factory.


Are the patch bays with XLR's isolated from rack ground?

[JFreak]

Originally Posted by musicman691

Are the patch bays with XLR's isolated from rack ground?

Good question, and does the hum stop with ground lifted?

[albee1952]

Question: Are the bays using individual grounds or are they all bussed together? Whatever they are set to, maybe changing to the other method will help You might also reach out to the company that makes the patchbays and see if they have any solutions

[Southsidemusic]

Thank you guys for all your tips. Going to pull out some units from rack 1 and 2 and see what happens if they arem’t in the racks and also check the Patchbays thouroughly and will report back.

Gonna check grounding etc tonight and make sure all that is OK. We dont have any issues when the gear that hum are ON but as soon as we turn off them hum appears if they are patched in.

Stay Tuned and again Really appreciate your knowledge.

[albee1952]

Originally Posted by Southsidemusic

Thank you guys for all your tips. Going to pull out some units from rack 1 and 2 and see what happens if they arem’t in the racks and also check the Patchbays thouroughly and will report back.

Gonna check grounding etc tonight and make sure all that is OK. We dont have any issues when the gear that hum are ON but as soon as we turn off them hum appears if they are patched in.

Stay Tuned and again Really appreciate your knowledge.

Hmmmm, how are you turning those units off? Does it happen in a way that might be dropping the ground? Would grounding all the rack rails to the same point be a solution?

[musicman691]

Originally Posted by albee1952

Hmmmm, how are you turning those units off? Does it happen in a way that might be dropping the ground? Would grounding all the rack rails to the same point be a solution?

That would be what's called a star ground and better than going from one rack to another to another.


Another possibility is that inside the gear the neutral and grounds are tied together. Not good.

[Southsidemusic]

Originally Posted by albee1952

Hmmmm, how are you turning those units off? Does it happen in a way that might be dropping the ground? Would grounding all the rack rails to the same point be a solution?

We have too much outboards now and we have to turn off some when not in use (well we dont Have to turn them off) but we turn them off with the power switch. However a few of the 1176’s and Neve dpa pres hum even if the power cord is pulled out of the unit or units. Thats why I think that it is some kind of voltage inside left in the units transformer or something causing this discrepancy as it disappers as soon as we turn thr units on again.
Never noticed thid before as we had all the gear incl the SSL4056 G+ console and 24” tape machine on all the time but as we dont use the 24” and the SSL all the time and neither all the analog toys i started turning off some of the units and left the patch canles still be inserted and heard that some of them would hum and were amitting an annoying noise so this started becomming evident just a few weeks ago and a few guys have re-soldered all the Mogami cables and Neutrik connectors on the affected units this past week and now we are gonna start testing the cables again and make sure all of the soldering is 100 and see if the noise disappers.

I talked to Neve Techs in the US this morning and they said that older units can have that annoyance as said in the first few posts from James and Darryl and I still wanna see if we can eliminate as many units as possible so if there are a few left that hum by design if not powered on but patched in then we can live with that but our Bluestripes and Rev F’s are causing annoying hums if turned off but as stated by many here, it is not a really big issue as it doesn’t happen when we turn them on and leaving units patched in and turned off while using other gear might be a stupid idea anyway.

Will keep on this tonight and try all your tips.

[gives]

Originally Posted by Southsidemusic

Hi Friends

I am going insane with this issue we are having now.

Background info and explanation:

Bought a crapload of new analog gear for the big room lately and now we have soo much analog toys we tend to turn off a few of the racks as the power needed to run all that is enough for a small village.

So everything has Neutrik connections and Mogami cables attached into 3 balanced patchbays of high quality.

The issue:

When we powered off the racks and only have say one rack filled with gear ON but the other racks which have all the gear turned OFF but still have some units in those racks patched into the Patchbays (with the units power OFF) we get a damn HUM low irritating as hell.

We tried all the tricks like swapping power outlets, checking cables and all that and every piece of gear in our studio goes into a seperate socket in the power conditioners and not one analog synth or outboard share sockets in the power units.

The weird thing:

When we power ON the units that are patched in and cause the hum noise the hum and noise disappears.

So in conclusion:

If we turn ON ALL the outboards and the same patch settings kept no noise at all but as soon as we power off the units still patched in the bayw some make a low noise hum like 1176’s, Neve 1073 pre’s, WA Buscomp, Bluestripe Rev A and Rev F
But not say Monster-2, WesAudio NG_Nuscomp, LA2A’s, Manley Comps and 500 series units etc etc etc ...

The culprits patched in but turned OFF like some pres and comps make the humming noise and as soon as we either pull out a patch cable or turn ON these units the humming is gone!

We never noticed before as all the studio runs off the same outlets so everything has been ON all the time which made the hum not there. But now with soo much gear we started turning off some of the units and racks and kept some patched in to the balanced patchbays and thats when we noticed that some units makes this humming sound until we either turn on the units or pull out the patch cable connection.

Does anyone here know why this only affect some outboard units and why the humming appear only when turned OFF and patched in and why other units doesn’t do this even though they are also patched in and turned OFF and why it disappeared when we turn these units ON again?

Thanks a million for any help as we googled and asked ans looked into verything we know like swapping cables in the patchbays and on the non humming units to the humming ones and vice versa but still only the same 8-10 units make this humming noise only when OFF patched in and stop of we unpatch or turn the. On.

All the best and let me know if more info is needed as I am going crazy for real and my stomach pain is maxed now.
Some units

If you are using any power strips that have surge/noise prior going into your power conditioning, that can totally cause problems. Also I have Equitech Balanced Power systems here for years and it's so quiet. Just another thing, I had a problem years ago when the rack itself was not grounding thing in it properly.
You probably covered this, but just thought I'd throw in on this-:)
Check out Equitech.. They are great and the people are still very helpful. The founder passed away unexpectedly a few years back, but the family and team are still going strong!
You are probably fine with your setup, but someone there might be able to help you out!
https://equitech.com