help me diagnose from another city

J

Jason Lavoie

Junior
Jan 13, 2011
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16
Ottawa
This is an installed system, has been in use for a few years, has a Shure SCM268 in one room that feeds into the main DSP

anything plugged into the SCM268 (customer's laptop, CD player in the rack, my NTI tester) all sound thin like they have a high-pass filter on, even though this mixer has no such features.
another similar input on the same zone sounds fine, so I swapped the cables at the DSP to rule out programming or I/O issues, and no change.
so I went to the 268 and plugged my NTI directly into the 268 with pink noise, sounds thin. pull the XLR output from the 268 and plugged the NTI tester directly to the cable headed for the DSP and it sounds fine!

ok, no problem right?, bad mixer (even though we've never had one fail before)
Only it's a 5h drive from here, so I shipped them a new mixer to install themselves, pretty confident that I'd found the problem.
They installed the new mixer and it sounds the same...

The only thing I can think of is a wiring problem that presents itself only with the 268 plugged in, but that the NTI circumvents?
Any thoughts?

Jason
 
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Re: help me diagnose from another city

SCM268 or SCM262?? SCM262 has stereo outputs. Is there an adapter cable from stereo-cinch to single-XLR/jack between the SCM262 and the DSP? You might be subtracting left and right... then you only hear the stereo content, which sounds thin most often ;-)
 
Re: help me diagnose from another city

Sorry, got my numbers mixed up. it is definitely a 268, with XLR output
Also, I was feeding it with a mono signal from my tester
 
Re: help me diagnose from another city

My guess would be that the cable from the SCM-268 to the DSP is faulty.

Your tester was probably driving the line with an electronic output stage whilst the SCM-268 has a transformer on the output.

I'll bet if you put a transformer on the output of your tester, then used the cable that should be plugged into the output of the SCM-268 which goes into the DSP, you would have heard the same "thin" sound.

I would inspect the connection where the cable terminates at the DSP. If it uses "Euro" connectors (or some similar variant) there are a lot of options for things to go wrong, especially if someone tinned the cable prior to inserting it into the connector and screwing it down. The connector may need to be tightened up. I would pull the cable out and cut off the solder tinned wires and re-terminate it with bare wires so that doesn't happen in the future. You may want to check any other similar connections.

Have fun and good luck!
 
Re: help me diagnose from another city

Josh Millward said:
My guess would be that the cable from the SCM-268 to the DSP is faulty.

Your tester was probably driving the line with an electronic output stage whilst the SCM-268 has a transformer on the output.

I'll bet if you put a transformer on the output of your tester, then used the cable that should be plugged into the output of the SCM-268 which goes into the DSP, you would have heard the same "thin" sound.

I would inspect the connection where the cable terminates at the DSP. If it uses "Euro" connectors (or some similar variant) there are a lot of options for things to go wrong, especially if someone tinned the cable prior to inserting it into the connector and screwing it down. The connector may need to be tightened up. I would pull the cable out and cut off the solder tinned wires and re-terminate it with bare wires so that doesn't happen in the future. You may want to check any other similar connections.

Have fun and good luck!
Click to expand...

yes, I forgot that the 268 has real transformers. that makes a bit of sense now.

unlikely to be a problem at the DSP end though because a) I already had my hands on that connector when I swapped them around to diagnose, and I always check for loose wires
and b) I did the original install and would never tin the wires. though it is surprising how many people will waste time and energy making something worse.

So either a bad XLR or broken wire. sounds like I'm headed back there no matter what
 
Re: help me diagnose from another city

Jason Lavoie said:
yes, I forgot that the 268 has real transformers. that makes a bit of sense now.

unlikely to be a problem at the DSP end though because a) I already had my hands on that connector when I swapped them around to diagnose, and I always check for loose wires
and b) I did the original install and would never tin the wires. though it is surprising how many people will waste time and energy making something worse.
Click to expand...

You know, I am constantly amazed at how poorly many people will terminate the wires in a system, regardless if it is XL connectors, crimp on connectors, or "Euro" terminal blocks. That is why it is always the first thing I will usually inspect. Of course, you also need to watch for wire insulation being pinched under the clamp, too. Though it sounds like you have figured out how to do it appropriately, which is a great thing! The gear is so much more reliable when the interconnecting cables are well constructed. ;-)

Jason Lavoie said:
So either a bad XLR or broken wire. sounds like I'm headed back there no matter what
Click to expand...
Yeah, that can be so frustrating and is usually the most expensive part.

Anyhow, I hope you can get them all sorted out!

Good luck and safe travels!
 
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