RFI with installed AMPS

[Billy Almaguer]

We have an X32 console with two digital snakes. I have an XLR output for my L, R, and Center channels. I have a Crown CTS 2000 amp (actually two of them). One for the mains (L & R) and one for the Subs (Center). I have the XLR from my Digital snake to to a bare connection (all of the inputs on my amps are bare connections). When I power my amp on I get radio interference. When I made the cables I simply took an XLR cable and cut the male end off...and then connecting the bare connection. I am not sure were the RFI is coming in from...I assume it's labeling. The amps are shielded against RFI. Do you have any thoughts or suggestions? Here is a link the amp: http://www.crownaudio.com/media/pdf/amps/137000.pdf

 

[TheWarrior]

Clipping an XLR like that turned that wire in to a radio antenna.

Not sure what you want to change, but something in that signal chain will need to go so your shielded wires, stay shielded!

 

[Billy Almaguer]

Yeah that's what I have deduced. I am going to go with this option...
http://www.fullcompass.com/prod/269562-Hosa-PHX-106F-BULK

...to get the input from my digital snake into the amp and ditch the homemade cable.

Thanks for the input!

 

[TheWarrior]

Bam! Enjoy!

 

[Billy Almaguer]

Thank you!

 

[Hi Ho]

Hope you get that figured out. The X32 is an awesome console. I use it as my main mixing rig and it has replaced every other piece of outboard gear I used to lug around with me. Total game changer in the mixing console world.

 

[WaynePflughaupt]

Yeah that's what I have deduced. I am going to go with this option...
http://www.fullcompass.com/prod/269562-Hosa-PHX-106F-BULK

...to get the input from my digital snake into the amp and ditch the homemade cable.

I’ll be surprised if it makes a difference. Aside from a bit of heat shrink, what’s the difference between the adapter you linked and your home-made cable?

I assure you, if you’ve ever seen a system that was installed by a sound company, you’d see that such “homemade” cables are the norm in professional installations. That’s why your amps, which were designed specifically for permanent installations, have barrier strips for inputs instead of XLR or 1/4" jacks. It’s common practice for installation techs to terminate connections on site using raw cable stock, to which they either solder XLR or 1/4” plugs or wire directly to the barrier strips.

If you got RFI merely from clipping a connector off a cable and then wiring the leads directly to the amp, either the cable is junk, the amp has issues, or maybe you didn’t wire it right.

And actually I’d be interested to find out if the interference is really RFI. RFI – radio frequency interference – means you’d be getting audio from a TV station, wireless mic transmission or something similar. Is this what you’re experiencing, or is it something else?

Regards,
Wayne A. Pflughaupt

 

[Billy Almaguer]

Hey Wayne! I discovered that my cable was built incorrectly (error on my part). The spec for the bare wire calls for +, shield, -. I has it as +,-,shield. I will rebuild my cable and see if that works out. I will say that I ran from my x32 to powered speakers and did not have an issue. When I introduced the amp that's where I picked up a radio station. Both amps are CTS 2000's. As soon as I begin rolling put the gain on the back of the amps I begin to hear a radio station. I assume it's my cable...perhaps not....but I will start there. I will post back the results tomorrow. Thanks for the input!

 

[Billy Almaguer]

Follow up...redid my cables....made sure my pins on the XLR lined up with what my connector was set up as and the discovered I had a made them incorrectly. I corrected the problem and now I am enjoying a beautiful sound. Thanks for the input everyone!

 

[Speedskater]

Getting back to terminal strip interconnect connections. For decades broadcast audio equipment was made with terminal strip connects. And that equipment worked just fine in the same room as big powerful AM, FM & TV transmitters.

 

[highfigh]

Hey Wayne! I discovered that my cable was built incorrectly (error on my part). The spec for the bare wire calls for +, shield, -. I has it as +,-,shield.

For clarity, can you post what you mean by "The spec for the bare wire calls for +, shield, -. I has it as +,-,shield."?

Pin 1 is always Ground, Pin 2 is Signal + (also called Hot or Normal) and Pin 3 is Signal - (also called Cold or Signal inverted) and the shield is always connected to Pin 1. Your choice of the color used for Pin 2, but usually, it's the one that's not black.