ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Cable Connection Dilemma  (Read 1314 times)

Alex Courtney

  • Newbie
  • *
  • Offline Offline
  • Posts: 13
Cable Connection Dilemma
« on: November 26, 2006, 01:41:19 am »

First, I want to thank all you kind folk who post here.  

I have a cable connection dilemma.  Sorry its long.  

A few days ago I asked what cable gauge would work to wire up a line level monitor send from our FOH console (Mackie CFX20-wanted to use an Aux send).  With great kindness and patience, Ivan responded with an answer.  Now I'm trying Ivan's and the Board's collective patience.  After posting  Embarassed , I took a look at our snake box and noticed that it had 4 returns, A,B,C,D (2 feeding the mains and 2 unused).  See picture below, although ours is about 18 years old, it looks and appears to function the same (same brand too).  So I dug around the other end of the snake at the FOH console and found 2 unused return cables buried among the stuff (1 XLR female jack-labeled “C” and 1 TRS male jack-labeled “D”).  The 2 returns on the snake feeding the mains are XLR female jacks labeled “A” & “B”.  It is apparent to my untrained eye that “D” was likely an XLR female jack that was changed to a TRS male jack.  Anyway, I thought this would be good, since we could run an additional monitor mix no problem.  No extra cable running needed.  Smile  And since we had 2 returns, could switch the monitors (2 of them), which are currently being run off a separate console located at the back corner of the platform, to the FOH console.  

For us, running monitors from a separate console has several problems (hey, this was done 18 years ago and not by me, I was only 12 at the time)
1) No one to run the monitor console (18 years ago I guess someone did).
2) Monitor console only has 12 inputs (fed by 12 splitter boxes) and we currently use up to 16 at FOH.
3) When playing soundtracks patched in an open stereo channel at FOH console, no sound through monitors.  This makes it difficult for vocalists to hear the soundtrack loud enough to sing along to (without blasting the FOH mains and the congregation).
4) Monitor console is getting old and doesn’t sound that good.
5) A whole host of problems can arise from #1. Sad

Solution:  Run the monitors from the FOH console.  As a bonus, we could add additional monitor mixes with AUX 2.

The Troubleshooting begins:
Channel “C” trouble. To try “C” I needed an adapter cord for “C’s” XLR female input since AUX send is TRS.  So I tried a TRS male to XLR male plug adapter cord into the XLR female “C” return. I had to turn up the AUX send on the channel and the AUX master section to almost the max and then I could hear faint signal from the monitors, same from the AUX 2 jack.  Now for the interesting part.  Then I plugged a TS jack into AUX with the other end of the TS jack cord going into a Hi-Z to Lo-Z transformer then to “C’s” XLR female jack.  And it worked well.  I then plugged “C,” XLR female with no adapters, into the console’s main left XLR out and it worked well too, with good signal to the monitors.

To rule out that the TRS male to XLR male cable wasn’t defective, I used it to go from the channel “B” on the snake box TRS out to an XLR cable running to the FOH mains and it worked fine.  So I don’t think the TRS male to XLR male adapter cable is defective.

Channel “D” trouble.  I plugged the TRS male jack “D” into the AUX 1 and same result as “C” with the adapter cable, very low output volume.  Same result in AUX 2.  I unplugged the XLR main outs and tried the main TRS out, same result as AUX 1 and 2, very low output volume.  Curious, I unscrewed the “D” TRS cable connector and noticed that the wires were White-tip and Yellow-ring with ground to the sleeve.  The solder connections looked good.  But I don’t know which color is hot and which is cold.

Questions Confused :
1) Why won’t the TRS male to XLR male adapter cable work with channel “C” return cable when a TS cable converted to balanced then to “C” will?
2) Why won’t TRS channel “D” work, could the TRS male connector be incorrectly wired?

index.php/fa/68/0/

Thanks for making it this far.
Logged
Alex

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 963
Re: Cable Connection Dilemma
« Reply #1 on: November 26, 2006, 09:09:27 am »

First of all, things were different back then.  A lot of gear did not have balanced inputs/outputs.  Heck even some of the "best" gear (KT-BSS-Crown) came standard with unbalanced connections.

Chances are good that the problem is inside your snake with the 2 "hot" wires tied together  on the tip of the 1/4".  When you plug into the 1/4" snake jack do you feel 1 "click-or pressure point" or 2?  If you only feel 1, then chances are that is your problem.

Take you snake head apart and give a look.  The wire is probably good, you just need to change 1/4" connectors.  If you change them, be sure to keep the ground isolated from the chassis with the little washers on the sleeve of the old connector.

I would avoid using the XLR/TS transformers (assuming you are using the barrell type) as they are designed for mic level signals and not line level.  You will not damage anything, but if you drive them moderately hard they will overload and distort.

If this is what you "must" do, then get a line level direct box that has a larger transformer in it to take the level.
Logged
Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.

Kevin Hoober

  • Full Member
  • ***
  • Offline Offline
  • Posts: 136
    • http://www.pinelake.org
Re: Cable Connection Dilemma
« Reply #2 on: November 26, 2006, 12:36:54 pm »

Hey Alex,

I have another thought...are you shure that the aux outputs of the console are balanced (in any way, shape, or form)  If that desk is 18 years old, (aka, not the new cfx-20mkII) the aux outs may be just TS unbalanced (guessing).  This would explain the weird behavior of working w/ the mains out but not the aux out (on 'C').  If this is the case, a line level transformer would be your fix.

Good luck,
Kevin
Logged

Alex Courtney

  • Newbie
  • *
  • Offline Offline
  • Posts: 13
Re: Cable Connection Dilemma
« Reply #3 on: November 26, 2006, 02:19:07 pm »

You guys are great here.

Ivan, you are correct, 1 click on the 1/4" snake box jack.

Ivan wrote
Quote:

I would avoid using the XLR/TS transformers (assuming you are using the barrell type) as they are designed for mic level signals and not line level. You will not damage anything, but if you drive them moderately hard they will overload and distort.

You also answered another question before I asked.  As I turned up the AUX send master volume I noticed distortion, especially in the lower frequencies.

Ivan wrote
Quote:

Take you snake head apart and give a look. The wire is probably good, you just need to change 1/4" connectors. If you change them, be sure to keep the ground isolated from the chassis with the little washers on the sleeve of the old connector.

Are you saying to take apart the snake box and look at the 1/4" connector jack?  That if those 4 1/4" jacks on the snake box were changed to TRS balanced 1/4" jacks, the unbalanced box would become balanced, thus solving the dilemma?  


Kevin wrote
Quote:

I have another thought...are you shure that the aux outputs of the console are balanced (in any way, shape, or form) If that desk is 18 years old, (aka, not the new cfx-20mkII) the aux outs may be just TS unbalanced (guessing).

Kevin, I wasn't clear enough.  The 18 year console is the monitor console.  The FOH Mackie CFX20 is about 4 years old.  But I did check the manual based on your suggestion.  Our Mackie CFX20 manual states that the AUX jacks are TRS, and they do have 2 clicks when inserting a 1/4" plug.  

But Kevin, you raise an interesting question.  Why will the balanced XLR jacks work from the Mackie CFX20 (i.e. running the mains) but the balanced 1/4" jacks from the Mackie won't?
Logged
Alex

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 963
Re: Cable Connection Dilemma
« Reply #4 on: November 26, 2006, 07:52:53 pm »

Of course you have to put a TRS jack in the box and either a TRS or XLR plug as needed on the other end. The cable should have 2 conductors and a shield.  It would be VERY rare if it was just an unbalanced line.

A balanced line is more the way the cable is wired as opposed to the type of cable it is.

You can test this by using a regular speaker cable as a balanced line cable-hooking it up to pins 2 and 3 and leaving the shield dicsonnected.  As long as you have a good twist ratio, you will probably not have any noise issues.  This is not recommended, but more to show a point.

When was the last time you say a telephone cable that had a shield?  They run for many miles with no issues.  Balancing is the "magic" that makes it work.

The success of balanced is largely related to the equipment on both ends not the wire used.
Logged
Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.

ProSoundWeb Community

Re: Cable Connection Dilemma
« Reply #4 on: November 26, 2006, 07:52:53 pm »


Pages: [1]   Go Up
 



Page created in 0.041 seconds with 22 queries.