The No.1 Website for Pro Audio
 All  This Thread  Reviews  Gear Database  Gear for sale     Latest  Trending
Hum help!
Old 11th May 2019
  #1
Gear Head
 

Hum help!

Hi Guys,

First of all, sorry to bother you with this, but it is soooo annoying.
I have a damn hum in my fancy new home studio and I can't eliminate it.

I'm from Europe, 220V in the wall, all in all, all of gear was "humless" until yesterday.
I tried to connect the studio into the hi-fi system.
Let me explain.

The room is around 30m2 big, one half is my hobby studio, the other half is a hi-fi/tv/gaming stuff.
There I have a Yamaha amp, turntable, etc.

I've installed earlier a long RCA cable, around 12 meters long, from the amp, to the rack, where it is connected into the patch panel, so, my idea was, I could record from the hi-fi (from tv, turntable, cd even cassette) and, If I re-patch it, I can hear my computer through the hi-fi.

The first problem is that the cable, even it is 12 meters long, was not long enough, so I had to buy those small plastic double female extenders and another RCA cable. At end of this, there are two of those well known RCA to Jack adapters.

The studio and the hifi is running from the same power, I mean, from the wall, of course, but literally from the same power line.
Both grounded correctly, each is humless on its own.

I think the problem comes from the cable, possibly from the extension or from the jack adapters...

I've tried to hook it up directly to the audio interface (UMC1820), no luck...

If I use my laptop, no hum.

Could it be the adapter?
Or the extension?
Or the RCA itself?
Old 11th May 2019
  #2
Lives for gear
 
Richard Crowley's Avatar
 

The problem could be from noise pickup along the rather long UNbalanced cable interconnection between the production system and the entertainment system. Even if the two systems are running from the same power mains branch circuit, there is still the possibility of a ground loop betwen the two due to the distance involved.

The test for length wold be to disconnect and short-out the interconnection cable at the entertainment system end and then listen to the cable at the production system. Is there still hum when the cable is intact but isolated from the entertainment system? And then the same test with the long interconnect cable disconnected at the production system. Do you hear the hum when listening on the long cable at the entertainment system end?

If the hum goes away, that suggests that the problem may be a ground loop between the systems. So, the solution could be an isolation transformer for example the Behringer Behringer HD400 https://www.thomann.de/gb/behringer_microhd_hd400.htm

But if the hum is still there, it suggests that the hum is being picked up along the path of the very long UNbalanced line. So, the solution could be to use a BALANCED line between the different systems. Again, a transformer like that Behringer HD400 could be used at EACH END to convert between unbalanced (most likely at the entertainment system end) to balanced for the long distance route. Then it would be appropriate to use balanced (shielded pair) cable like micophone cable for the long distance. It is exactly problems like this that we use balanced interconnections for pro gear (mic-level and line-level).
Old 11th May 2019
  #3
Gear Head
 

Quote:
Originally Posted by Richard Crowley View Post
The problem could be from noise pickup along the rather long UNbalanced cable interconnection between the production system and the entertainment system. Even if the two systems are running from the same power mains branch circuit, there is still the possibility of a ground loop betwen the two due to the distance involved.

The test for length wold be to disconnect and short-out the interconnection cable at the entertainment system end and then listen to the cable at the production system. Is there still hum when the cable is intact but isolated from the entertainment system? And then the same test with the long interconnect cable disconnected at the production system. Do you hear the hum when listening on the long cable at the entertainment system end?

If the hum goes away, that suggests that the problem may be a ground loop between the systems. So, the solution could be an isolation transformer for example the Behringer Behringer HD400 https://www.thomann.de/gb/behringer_microhd_hd400.htm

But if the hum is still there, it suggests that the hum is being picked up along the path of the very long UNbalanced line. So, the solution could be to use a BALANCED line between the different systems. Again, a transformer like that Behringer HD400 could be used at EACH END to convert between unbalanced (most likely at the entertainment system end) to balanced for the long distance route. Then it would be appropriate to use balanced (shielded pair) cable like micophone cable for the long distance. It is exactly problems like this that we use balanced interconnections for pro gear (mic-level and line-level).
Yeah, that also could be.
But, you won't believe it.
Just, as a last idea, I've replaced the power distributor at the hi-fi (there was only 1 wall plug, I needed two), and hum disappeard.
Not entirely, but you know, I have to crank up the volume all the way up to hear it.
So, snaper is smiling right now :D
Old 11th May 2019
  #4
Lives for gear
 
Richard Crowley's Avatar
 

All's well that ends well. (Bill Shakespeare)
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump