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[Billy Snody]

Good day sir.
My name is Billy Snody. I saw some of your posts on a pro sound web forum and was hoping to get some ideas. I am a rookie chasing a “wabbit.” I am working on chasing an intermittent muting of the house channels in our Church. I am new to this and am tackling it because I am tired of it occurring. I live in a spot in a chug hole with no one to turn to for assistance. The company that sold and installed us is out of business. Our system is about five years old and started this “muting” activity about a year and a half ago and is getting more frequent. We have an Allen Heath GL2400-32 mixer, XLR “M” is outputting to a Sabine NAV 360, input 1 only, (nothing from mixer L or R which makes little sense to me) and nothing to input 2 or 3 on the Sabine. So one input to the DSP. From there it sends channel 1 and 2 out to a QSC RMX1850HD amp in stereo and then to house speakers hanging way up in ceiling, 2 paralleled (3.3 ohms on dvom)on one channel flanking the center speaker (5.7 ohms on dvom)wired solo on the other. Mixer AUX 1 and 2 go out on TRS connections into XLR’s plugging into a DBX 231 EQ whose outputs feed a QSC RMX1450 in stereo to the 3 stage monitors through floor boxes for I/O. My quandary is that the Sabine only has the 1 input connected but it has 3 outputs connected. I just got software for the Sabine and am sure it is going to blow my mind when I connect and see what this is all about. By the way, the input and output connections on the Sabine are all bare wires into small multi-terminal connectors (Phoenix connectors maybe). Output 1 and 2 got to the main (FOH) amp. Output three is a cable bundled with our 2 main speaker wires to somewhere/something that I have yet to determine. Our organ outputs to a passive x-over network with its own speaker array. Might you have any suggestions what I should look for to find out what this third output is connected to, even if I have to go up into the ceiling. We have no subs anywhere. We do have a lighting control box for some stage lighting that is also malfunctioning but I have found nothing but a power wire and a control wire that leads up to the power packs plugged into that controller. I have sent the FOH amp to a QSC authorized repair center for a diagnosis, a physical so to speak. I moved the inputs and outputs from the house amp to the monitor amp and my muting followed my move. I wanted to make sure the house amp had not been damaged. We have a Furman PS8R 15 amp sequencer and an M-8X2 conditioner for supply. They are on a 20 amp breaker. QSC tech’s and Furman told me all should be well as far as electrical supply goes. I was trying to bypass the Sabine but with only 1 output “M” from the mixer I don’t know if it is safe to drive an amp on only one channel at a time. Have you ever heard of a DSP’s output signal being intermittent. I think bypassing the Sabine is my next logical step but how to do it without messing something else up. Would you agree? Sorry for the length. Any suggestions appreciated.
Thanks, Billy.

response to email to Mr. Spense and I thank you so much for the input and helpful suggestion!

The single out of the mixer simply means your speaker system runs in mono. Pretty normal. The first 2 outputs are from a crossover in the NAV. One will be HF and the other LF. The third output likely feeds another room, possibly the foyer or a basement overflow room.

I suggest you post your pretty well written description in the church sound forum. Don't forget to have your display name be set to your real name.
In the forum, not only will you get more eyes on your problem, but others may learn from the dialog.

You use the term muting but do you simply mean the sound is silenced periodically?
How long does the sound go away and how often?

You have an install version of the NAV which is why the connector blocks.
I use a NAV480 and it has level indicators on the front for all inputs and outputs.
Look at them when the sound drops and see if it is an input or an output?

Good luck and see you on the forums.


Rob Spence
Lynx Audio Services
" We Get Live!"

I learned today that we have a "Gigrac" 1000st in our fellowship hall that is connected to our sound system. I was unaware of this and thought it was a separate system on its own. I'll bet that this is the elusive third connection. By the way, do the green "Phoenix" connectors unplug from the back of the NAV 360 before I do some damage or must I unscrew the leads from them?
Thanks for the help!

[Kyle Waters]

Does the system mute at a certain time?  Loud music etc?

[Mike Caldwell]

As mentioned, when the system mutes check and see what level meters
are showing any signal level. I the DSP input meter still shows signal your mixer is not the problem, if the output meters sill show signal level most likely the DSP is not the problem, though it maybe possible that the meters would show an output level and the actual outputs are dead/muted.

If the meters on the DSP all show signal level when the main system mutes do you have signal to the system in the fellowship hall?

When the system mutes check if you see any of the green signal
lights on the QSC amp are still blinking showing that the amp is getting audio signal.

Does the system start acting up at random times or only after it have been turned a while.

What does it take to make the system un-mute after it has muted or is it a fast in and out of mute at random times.

From your description of the speaker wiring it sounds like the speakers are passive so the DSP is more than likely providing high pass filtering, EQ and limiting, than again depending on the installer it maybe acting as no more than a line level split feeding the three amp inputs.

To bypass the dsp all you need to do is take a mic cable from the output on the mixer and connect it directly to the amps input.

[Stephen Swaffer]

One possibilty and a simple check is that the M output is dropping out do to an internal intermittent connection.

Since L & R are unused I assume you are running mono. In that case, as long as all pans are centered, you should be able to run off L or R just like M so switch to one of those and use its master as the sytem master see if the problem continues.

You are headed the right way seeing that the problem continued with a different amp- just need to think through what you change to see what the problem follows.

[Billy Snody]

The system mutes totally at random, with and without instruments and or vocals, sometimes briefly and sometimes for an extended period. it has muted for as long as thirty-ish minutes on a couple of instances. I don't know if it is related but when it mutes I always attenuate the levels on the mixer because when it comes back on it is usually LOUD if I don't adjust it before.

[Billy Snody]

If things go as planed I am going to connect do the DSP this weekend and see if I can notice what is happening. From what I've been able to tell so far the three main speakers are all running full range as we have no subs and no outboard crossovers between the EQ or the DSP and the amps. The DBX EQ is strictly on the stage monitor circuit which as far as I can tell is not effected by the "muting" scenario. I think you may be correct with the line level splitter being the primary reason for the DSP. If I attenuate the L or R main slider it does change the overall volume level and texture of the sound. We do have all three (LRM) up near 0 in normal operation. Questions does "unity" equal "0" and should I found a switch somewhere on the mixer for stereo/mono output. I think you are saying unplug the "M" XLR and move it to "L" or "R" and see if the condition follows.

[Billy Snody]

I forgot to mention that when this muting happens I never lose the power lamps or cooling fans on either amp. Most of the time I do lose the signal lights on the house amp (sometimes they just get very dim)but never on the monitor amp and have yet to see a clip light on either amp. The only time I ever see a clip level on the mixer is once in a while when on our Pastors wireless channel as his mic is fairly sensitive and he projects well. We usually have his channel below 0 around 15 on the slider I think.

[Rob Spence]

One thing I didn't ask was where are you located? There are forum members in the darnnest places.


Sent from my iPad using Tapatalk HD

[g'bye, Dick Rees]

I just Googled the 1850 manual.  Page 19 addresses safe operating levels and cooling issues:  ventilation/airflow.

Page 23 addresses the auto-muting brought on by excessive interior temperatures.

A good guess would be that something like clogged filters (have they EVER been cleaned?) or obstruction of the intake of cooling air or the exhausting of heated air has happened.

Check these issues.  Cleaning the filters is simple.  Insuring unrestricted air flow is likewise a simple matter.  If the filters are obviously clogged from lack of the recommended periodic maintenance it might be advisable to have an electronics repairman remove the casing and blow any dust and dirt out of the interior.

As always, the first thing to do before WAGing is to RTBM.

Good luck.

[Keith Broughton]

I just Googled the 1850 manual.  Page 19 addresses safe operating levels and cooling issues:  ventilation/airflow.

Page 23 addresses the auto-muting brought on by excessive interior temperatures.

I'm with Dick on this one.
Considering the timing and duration of the mute, overheated amps could be the issue.
Start there and work back.

[ProSoundWeb Community]