Interconnects to/from professional xover

[scottjoplin]

I would call it a problem.

 

[NicMac]

However, I build my cables with CAT5 solid core twisted pairs terminated with rca for unbalanced connections. I always found they sound very good and cost nothing. The problem is that this way I don't have a shield.

Use one wire of each pair as shield and the remaining 4 for the signal. Maybe not the best shield in the world, but the wires are twisted.
One cable run for a stereo connection.

 

[PRR]

In many cases, un-shielded lines work fine. Short runs in benign rooms, anything may work. (If it doesn't, you have probably mis-understood the connection; shielding will not cure all errors.)

And in this pre-->Xover run the input is differential so much induced crap is rejected to some degree.

I have run slightly-boosted microphone signals in >100 feet of cheap CAT3 cable overhead in a school. Electrical interference was very low. Despite a purely unbalanced receiver. (The sources did float.)

 

[scottjoplin]

It depends what you mean by work (fine). Some RFI may not be heard, it may be heard and it's effect preferred, it may cause ultrasonic oscillation.

 

[H713]

Galu was almost there, but the full truth is that you need TWO DIFFERENT CABLES depending and who´s sending and who´s receiving.

The problem being that modern equipment does NOT have true transformer balanced outputs or inputs which was the original spec but it is EMULATED by using 2 UNBALANCED outputs or inputs which are electronically out of phase to achieve the balancing benefits but there is a compromise involved.

main problem being that like on any active device, amp or preamp, you must NOT ground outputs.
No big deal on grounding inputs though. Like on any preamp or power amp.

As in: do NOT ground pin 2 or 3 at the output/send side.

So for the RCA SEND to XLR RECEIVE cable you use #17
pins 2 and 3 can be safely joined.


and for the XLR SEND to RCA RECEIVE you use #4
Notice pin 3 is NC: NOT CONNECTED
http://kb.inmusicbrands.com/media/images/rane/n110fig4a.png

Mark your cables accordingly, as in using a piece of Red tape around SEND end and Blue/Green/White/Yellow (your choice) at the RECEIVE end

Plan B, "almost universal safe cable"
make all like #4 , with Pin 3 UNCONNECTED


Why "almost" universal?

because it will work with ALL MODERN (electronically balanced) equipment, but not with the old style true transformer balanced type.
Which you will almost never find anyway (scarce and expensive).

To make an already annoyingly complicated situation even more complicated, some electronically balanced outputs are designed to emulate a transformer, and you DO want to ground one side of them. I believe that some of the THAT balanced line drivers work this way as well. A bit more information can be found on Douglas Self's website (better yet, consult his book).
Balanced Line Technology

It's even more fun with old equipment, particularly from the UK, where it's wired for pin-3 hot.