Interconnects

[Moondog55]

Query here as we don't have an interconnect subsection.

I need to split the output from my Behringer CX2310 electronic XO to drive two stereo subwoofer amps.
Should I follow the directions in the Behringer manual and connect Cold and shield at the XLR connector OR should I follow the advice on D Self web page and connect the Cold and shield at the RCA end

http://www.dself.dsl.pipex.com/ampin...balanced.htm#6

I am battling to get rid of the earth hum and want to keep any introduced noise to the minimum

[infinia]

This is just a general guide that works 90% as every system is unique.
It's best to connect shields of a twisted pair only at the receive end. A single conn. limits ground loop problems, as stray currents tend to flow from one box to another. Shielding is still effective and is referenced to the quieter grounds.
An exception could be if the receive end box has no quiet earth connection and the send box does, then the single shield connection would be made at the sending side only. Even this example could be a problem if the receive end gnd noise is purely common mode.

[Moondog55]

Thanx Infinia, I should have been more explicit, I've only got single conductor shielded cable in the drawer, should I go and by twin and shield??

[infinia]

Yes that's what audio using 3 pin XLR expects. but you could use what you already have. I really don't like any audio signal currents running thru my shields or chassis.

[Moondog55]

OK; I walked down and bought some 2-core plus shield, a meter of Proel microphone cable and a meter of some lighter weight stuff.

The Proel is much higher quality but I can't get both protective sheaths into the XLRs end as it is designed for a single 6mm cable, and the Proel is already 6mm in diameter> can I trim the sheath off with out any effect on signal?? or should I use the smaller cheap stuff.

In short runs how important is inner conductor size anyway, will the small stuff make any audible difference over 200mm??

http://search.dse.com.au/search?w=sh...e01071d&ts=new

Centre Conductors: 7 x 0.12mm copper, Shielding: 32 x 0.12mm, spiral wrapped, Diameter: 4mm OD, Nom. Capacitance: 210pF/m (Conductor-shield).

[infinia]

I don't know about the conductor sizes AWG> mm illiterate.

Do you have a ground loop problems "earth hum" with the coax?

What gear has earth connections?

edit> I think Linkwitz has a good diagram of converting XLR to single ended on his DIY mic preamp. (terminates the unused inner signal with the same resistor)

[Moondog55]

Everything is double insulated except for the XO unit, I use a common power-board for surge protection, the earth hum is definitely from the Behringer unit ( it is probably in need of replacement- they do not age gracefully )

[infinia]

Hmm that's weird about the Beh. how did you have it Beh. ins/outs hooked up before?

[Moondog55]

It is definitely the XO unit; when I move the dial to around 300/500 the hum completely disappears.
I'll bring in the spare CX unit and hook it up when I finish fixing my broken sewer pipe, I guess I'm just lucky because it just started to pour with rain