Hello and thank you in advance for the eventual help.
That's a very technique question this one I'm going to ask, for technicians with electric systems knowledge and experience too.
Put the case that you have 2 separated switches and electric lines from your switchboard, one for all your studio equipment AND one for the guitar and bass amplifiers. So you connect the mixer, PC, cards, pres, speakers to line A outlets. Amplifiers to line B outlets. This to prevent interferences.
Now you have a line out or DI from the bass amp to be recorded through a mic pre. The first is powered by line B, the second by line A. Both lines are conditioned 230v 50Hz, and have the same cables diameter (4mm), same outlets model and so. The phase is always on the same outlet pole, It's IN PHASE.
Is it safe? Ground loops? Two devices plugged in different lines outlets but connected by an audio cable. Would you move the bass amp to the same mic pre A line?
Thanks for reading.

 

Last edited: May 21, 2016

Ha! That's a complex one!

Take a look here:

http://web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

 

hello thanx for the reply
nice one, I m saving it
I ve skipped to the chapter 5 where it talks electric power but I can t find an answer, I ll read it all later

 

anyway my concern isn t about ground loops, I know how to solve them
it s more about electric power, two different power lines connected by an audio cable from the out of a device on the B line to an input of a device on the A line.

 

Thing is that I am no expert. I am a mere 'dabbler' when it comes to electronics. I think when you said 'is it safe?' you might be referring to potential difference and if that's the case, then run from the same outlet would be safest.

The reason I posted the book, is because I was looking into the same subject matter as what you are doing and the ground loop stuff has been something I wanted to understand for years. I don't really get too many problems with it theses days but it's still interesting stuff. It was when I found that little book, that I really began to realise how little I actually know!

 

ok ok it s interesting indeed
saved to my folder, good to refresh memory
the potential difference is ok, all cables are 4mm, the 2 switches are identic.
I don t have ground loops, too. I ve build a secondary ground line for the racks chassis in case of loops
I ve never used it! if I knew it... cable, channels, work...

I have some knowledge, but I have this doubt since years
actually I have an Ashdown preamp for bass, then I use emulations, it s on the PC-DAW electric line
but sometimes bass players bring amps

 

Ground is the same ground for both A and B lines. Using a different wire won't make a difference. If
A and B both have a solid ground connection, it won't matter.

 

yes the ground point is the same
I have 2 ground points one for the house one for the studio, far from each other and from the buildings wall.
two completely separated systems, never in the same switchboard or channels.