How to make multicore cables, snakes. Wiring up setup. Advice Please.
Odeo
Thread Starter
#1
13th February 2005
Old 13th February 2005
  #1
Gear Head
 

Thread Starter
How to make multicore cables, snakes. Wiring up setup. Advice Please.

OK.

I have just bought enough lengths of multicore cables. I would like to know what's the best way of wiring up the connectors to get the best quality from them, like preventing ground loop etc.

I had a look and theres 20 mini cables (2 core and a shield) inside one big cable which has a shield that surrounds the mini cables inside it.

If I was to make XLR to XLR multicore snakes.
with the mini cables:
Do I leave one of the shield open while the other end of the shield is soldered to one of the connectors. If I do. Does it matter which end the open shield of the cable it connects to. eg. Mixer to Outboard. Also would it matter if I end up using that type of wiring for a mic cable where one end of the mic cables shield is open. Or that I may use a patchbay to patch microphones to my preamps which uses that one shield open cabling configuration.

with the big shield that surrounds the mini cables.
Do I leave both ends open. If not, what do I connect that to. If it was for a stage box. I would connect one end of the shield to the stagebox and the other open? is that right? For making XLR to XLR multicore cables, do I leave both ends of the big shields open?

Also has anyone heard of Alden multicore cables. It is made in USA. Whats your opinion of it or whats the general opinion of it. Is it anygood? Does anyone have any links to info on these types of cables. I have searched on the web and can't find any.

Ta
#2
13th February 2005
Old 13th February 2005
  #2
Gear nut
 
Matt M's Avatar
 

Wow. That's all a very big question. I'll do my best here....

First off it sounds like the cable you are using is very similar to Gepco multipair in that each individual pair (let's call them pairs not mini cables for clarity sake) is sheilded and then there is a large shield over the entire thing. Are the individual pairs insulated with a jacket or is the foil shield the outer visible layer? I am not familiar with Alden cable and it looks like a medical cable manufacturer on the web. You are sure this is not Belden right?

The question of how to terminate the shields to avoid ground loops is a difficult one. Proper studio ground systems take into account not only audio shielding but also equipment chassis grounding, facility power and ground distribution, patchbay grounding, etc. The ground configuration you are describing (with the shield lifted at one end) is referred to as a star ground system. It is also reffered to as telescoping your shields. Different techs will have different opinions relating to what grounding system is best but a properly implemented start ground system can be very quiet. Without getting into a very lengthy description on the finer points of star grounding I can say the following:

1. In a star ground system one end of each shield MUST terminate to clean ground path.
2. There are arguments for terminating the shields in a variety of ways but in your situation I would probably lift them at the gear end and tie them at patchbay. The patchbay must be ground bussed and this ground buss (or each ground buss if you have multiple bays) must be tied to a clean ground source (most likely a ground buss bar with a large dia wire which goes off to a ground stake , cold water pipe, etc)
3. Do not lift shields on your mic cables or mic tie lines. Phantom power will not work without the shields connected on both ends. There are also other reasons to tie the shield on both ends of your microphone wiring. This goes for the inputs to any mic pres as well. In larger systems where there is a dedicated mic patchbay this is the one bay that we do not buss.

If this all sounds like more than you want to deal with or if you have a relatively small system and are not using a patchbay you might consider starting off with the shields connected at both ends on all of your harnesses. You can always clip out the shields later. If you have a more extensive setup you may want to consult a professional to help determine the best course of action for your specific situation.
Odeo
Thread Starter
#3
14th February 2005
Old 14th February 2005
  #3
Gear Head
 

Thread Starter
so you are saying, do not cut the shield on any cables that will be plugged to a mic on one end. Besides, mics are there any other gear that I should not cut one end of the shields with.

As for the patchbay grounding. I have a rean and db trs patchbay, with those removable little circuit board blocks. Its not one of those industrail broadcast type expensive ones, these are like 100 us. So how do I ground that. The connectors on it is plastic, so even though the sockets of the patchbays touch the metal rack containment, it still does not conduct to the rack frame for me ground the rack frame. So do I just ignore grounding the patchbay.

It's definitely Alden, I still await receiving it though to confirm, but apparently it clearly states on it that its Alden made in USA.


Ta
#4
14th February 2005
Old 14th February 2005
  #4
Gear nut
 
Matt M's Avatar
 

Quote:
so you are saying, do not cut the shield on any cables that will be plugged to a mic on one end.
Yes that is correct

Quote:
Besides, mics are there any other gear that I should not cut one end of the shields with. As for the patchbay grounding. I have a rean and db trs patchbay, with those removable little circuit board blocks. Its not one of those industrail broadcast type expensive ones, these are like 100 us. So how do I ground that. The connectors on it is plastic, so even though the sockets of the patchbays touch the metal rack containment, it still does not conduct to the rack frame for me ground the rack frame. So do I just ignore grounding the patchbay.
I would start with all the shields connected on both ends. The type of patchbay you are describing rarely has provision for a ground buss. A improperly implemented star ground system can be very problematic.
Odeo
Thread Starter
#5
17th February 2005
Old 17th February 2005
  #5
Gear Head
 

Thread Starter
it seems like alot of hassle to do. I might just leave both shields connected.

I have both Belden and Alden cables, I have just received the Alden cables, their about 3-5 years old I guess. I bought them second hand. Im going to cut them up and make some nice length ones.

The Alden one has foil on the outside of each multipair with no foil that surrounds the multipairs as a whole. The Belden ones dont have the foil on the outside of each multipair but it has a big foil that surround the enclosed multipairs. That's where the shield is. I haven't cut up the Alden, so I dont know if theres a shield that surround the multipairs as a whole. Is having the foil on the outside of each multipair cable mean that it's a better quality cable that one that has the foil only on the cable as a whole.

I would like to know, coz the one that's of better qulity will be the one, I connect most of the high end gear with, and use the less quality one on the tape, cassetes, cds cabling.

Ta
#6
17th February 2005
Old 17th February 2005
  #6
Gear nut
 
Matt M's Avatar
 

Quote:
Is having the foil on the outside of each multipair cable mean that it's a better quality cable that one that has the foil only on the cable as a whole.
I would avoid anything that is not individually shielded.
Odeo
Thread Starter
#7
17th February 2005
Old 17th February 2005
  #7
Gear Head
 

Thread Starter
you said:
"I would avoid anything that is not individually shielded"

what do you mean by that. Do you mean the foil, or the ground wire. The Belden with the big foil and ground wire on the whole surrounding of the multipair together, which also has a ground wire on each multipair, but no foil on each individual multipair. Or The Alden has foil around the outside of each multipair, plus a ground wire inside each multipair.

Maybe I'm confusing the foil as shield?
So which is better?

Ta
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