SOLVED: Audio problem - HELP!

D

David W. Richardson

Chapelgrove Films
I am being trained, more or less, to take over videotaping the Sunday morning service at my church. So I've come into this whole hardware setup pretty much blind.

I've been observing the current guy for 2 weeks, and everything seems to work fine. But last Sunday, I had to do it on my own, as the regular guy had somewhere else to be.

There is no active monitoring of the sound, though there should be. Because we have a sound problem.

The camcorder is a Canon HF R500. The sound mixer is a SoundCraft Spirit Folio 10 2. Multiple input sources, both wired and wireless, connect to the mixer. The output is split (using a Radio Shack splitter) -- it appears to be a 1/4" mono jack, but plugged into it is a 1/4" stereo splitter that splits it to two 3.5mm stereo (I think) jacks. One of those is connected via a 3.5mm stereo male-to-male cable to the microphone input jack on the camcorder.

I know there are inherent problems with splitters as well as with connecting stereo plugs to mono jacks -- I assume the camera's microphone jack is mono, since it doesn't say anything in the manual about connecting a stereo mic. Be that as it may, this setup has been working fine for them, at least since I started being involved.

But on last Sunday's recording we had TERRIBLE static in the audio -- the static was almost louder than the people speaking. Very hard to hear them.

I've been studying things there. At first I thought I had it isolated to two possibilities -- either the cable that runs from the mixer to the camera, or the microphone jack of the camera itself. But I've replaced the cable and used a second (identical) camera, and still had the same problem.

They do also have an AV cable connected to the camera's output. (Made sure the camera was set to "AV" and not "headphones".) I had thought there might be some sort of loop or feedback situation, but that signal never returns to the mixer -- it goes to a DVD recorder, where it connects both video and audio to the inputs there.

The static noise does show up on the microphone volume level meter on the camera's screen. (Wish I'd noticed that on Sunday, but I still wouldn't have been able to fix it.)

I've disconnected everything from the camera except the mic cable to the mixer -- same problem. Even with the power turned OFF to everything but the camera -- mixer, DVD recorder, wireless receivers, etc.), I still get the same buzz/static when the cable is connected to the camera and the mixer.

If I drop the mic sliders on the mixer all the way down, the noise level decreases by about half, but it doesn't go away.

At this point I'm left with what appear to be two possibilities, although I'm no sound expert so there may be lots more that I'm not thinking of. First, that little Radio Shack splitter might be bad and need to be replaced. Or second, it could be a short or some other hardware problem inside the mixer itself.

There are cables running all over the place. It's like a rat's nest. But it was exactly that same way before, and they had no problem. As far as I know, nothing has been changed. (As far as I KNOW.....something could have been changed that I don't know about.)

It doesn't appear to have anything to do with any camera setting. Unless it's simply the plugging of a stereo plug into the camera's mono jack, then it would seem the problem is external to the camera.

Does anyone have any ideas? Sunday is coming, and those shut-ins need their DVDs.

Thanks in advance!
 
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Since we don't know your level of audio expertise, is it possible you may be mistaking 'static' for a ground-loop or EMI (electromagnetic interference) and is there a PA system integrated into this set-up?
Can you post a short audio clip, and explain in detail the signal flow with make and model number of the audio devices following the mixer (going to the cam).
If it happened all of a sudden, I would first recommend checking your all the cables from the mixer's output to the cam input. Either with a cable tester, multi-meter, or by substitution.
Based on your mixer and camera, I would also suspect your getting some kind distortion, overloading the camera's input, i.e., the camera's input is microphone (mic) level the Spirit Folio mixer's output is line level (-10 or +4dB), both of which would overdrive a mic level input, either occasionally or constant.
 
Rick R said:
Since we don't know your level of audio expertise, is it possible you may be mistaking 'static' for a ground-loop or EMI (electromagnetic interference) and is there a PA system integrated into this set-up?
Can you post a short audio clip, and explain in detail the signal flow with make and model number of the audio devices following the mixer (going to the cam).
If it happened all of a sudden, I would first recommend checking your all the cables from the mixer's output to the cam input. Either with a cable tester, multi-meter, or by substitution.
Based on your mixer and camera, I would also suspect your getting some kind distortion, overloading the camera's input, i.e., the camera's input is microphone (mic) level the Spirit Folio mixer's output is line level (-10 or +4dB), both of which would overdrive a mic level input, either occasionally or constant.
Click to expand...

I did replace the cable from the mixer to the cam. You may be right about it being a line level signal going into a mic input, but that would mean someone changed something somewhere since the Sunday before, and I am not knowledgeable enough on sound and mixers to know what to look for.

You can hear the sound for yourself -- http://pisgaharpchurch.org/mediacast/gods-way-to-greatest-usefulness-rev-charles-b-evans-iii/

Just click on 'Part 1'.
 
There doesn't appear to be any way to change the mic input on the camera from 'mic' to 'line', so I assume I need to ensure that the run from the mixer is at a 'mic' level. Not sure how to check that.
 
That my friend is a big AC hum. Remember that tone, when you hear it you know it's coming from ac power someplace. Most often a ground loop.

You have a very funky audio chain so it might also be a loose connection but my bet is on a ground loop. Now where the problem is can be tricky. Any computer connected to any part of the sound system is a likely suspect.

But if not that then it's going to be something that is plugged in to the wall. One quick and dirty way to check is to get a ground lifter (the three prong to two prong power cord adapters) and try that on any of the grounded power cords. Sometimes that will fix it. Also if there are any channels of the mixer that are not being used make sure the fader is down.

As a general note in a public space like this you pretty much have to assume that things have been messed with when you come in. You have a lot of hands with not a lot of knowledge (or worse just enough knowledge) and they will mess with settings etc.

On a longer term, I would rethink the setup. It sounds like the camera is not being used to record. If so it makes no sense to run sound through it. Going straight to the DVD recorder would be cleaner and get rid of a bunch of potential problem points.
 
- A signal level mismatch would not make a constant 'noise'.
- From what I hear, likely a ground loop or a faulty cable.
- "MIX (R) jack" would be the main out Right channel, which 'should' be noise free. What's plugged into the left? If that feeds the PA, try temporarily disconnecting it for trouble-shooting purposes. If the noise stops, check/replace the cables feeding the PA.
No change: try disconnecting the direct-in instruments one at a time from the mixer end. (typically.. keys, bass, acoustic guitars). If it doesn't stop, try the mic inputs one at a time (no change would eliminate an input issue).
 
Thanks to both of you for the advice!

There's no computer connected anywhere, as far as I know.

I'll try unplugging power to things one by one, to see if anything alleviates the problem. I don't think anything has been plugged in since the last time it worked, though. But it still bears investigating.

I'll make sure the faders on unused channels are turned down.

The camera actually is being used to record, as well as the external DVD recorder. Someone takes the recorded DVD and immediately makes copies, which are delivered to the shut-ins that very afternoon. The footage from the camera card is uploaded to the web -- that's what you saw from the link I posted. The people who do all of this are not very savvy on technical things -- they don't pull the footage into an NLE, trim it, add titles, etc. They just take the files straight from the card and FTP them. I'm going to try to get them to let me bring the card home after each service so I can edit the files, export them to something smaller, and do the uploads for them -- or at least bring them back the smaller, edited files so it will cut their upload times.
 
Rick R said:
- A signal level mismatch would not make a constant 'noise'.
- From what I hear, likely a ground loop or a faulty cable.
- "MIX (R) jack" would be the main out Right channel, which 'should' be noise free. What's plugged into the left? If that feeds the PA, try temporarily disconnecting it for trouble-shooting purposes. If the noise stops, check/replace the cables feeding the PA.
No change: try disconnecting the direct-in instruments one at a time from the mixer end. (typically.. keys, bass, acoustic guitars). If it doesn't stop, try the mic inputs one at a time (no change would eliminate an input issue).
Click to expand...

I only played a few seconds of both 'Part 1' and 'Part 2', but it seems to me the noise was not as loud at the beginning of Part 2. That person (the preacher) was wearing a wireless mic, which may have made a difference in the signal-to-noise ratio. Just speculating.

I'm not sure what is plugged into the left, but I don't think it feeds the PA. I'll check on that.

The only instrument is the organ. All of the rest are various kinds of mics for vocals.

Thanks for the help! This all gives me something to pursue.
 
Start over and isolate the problem.

Disconnect everything from the camera, including the DVD recorder. The buzz should not be there since you said you tried this with two different cameras. Is the buzz there?
Add the DVD recorder - test again
Add the mixer cable without the mixer or the other thing connected to that splitter cable (you didn't say what it is. Is it the PA?) - test again
Add the other thing that is connected to the splitter - test again
Add the mixer - test again

....and so on. Just add one thing at a time until you hear the noise. Let us know what you find out.
 
Paul F said:
Start over and isolate the problem.

Disconnect everything from the camera, including the DVD recorder. The buzz should not be there since you said you tried this with two different cameras. Is the buzz there?
Add the DVD recorder - test again
Add the mixer cable without the mixer or the other thing connected to that splitter cable (you didn't say what it is. Is it the PA?) - test again
Add the other thing that is connected to the splitter - test again
Add the mixer - test again

....and so on. Just add one thing at a time until you hear the noise. Let us know what you find out.
Click to expand...

1. Did that. No buzz with nothing connected.
2. No buzz with the DVD recorder alone connected.
3. Buzz with the mixing board cable alone connected. Buzz continues whether DVD recorder is connected or not.
4. I don't know what the other cable on the splitter connects to. I probably won't be able to get back there to find out until Saturday morning.
5. I pulled the splitter from the board, but left everything connected to it -- the cam and whatever the other cable runs to. No buzz.

The one odd thing is this -- when the cable is connected to mixer and cam, the buzz doesn't instantly appear. Watching the level indicator, it takes 2 or 3 seconds before it shows the buzz. Then it shows it very low, and it builds up over the course of maybe 5 seconds or so until it's at its constant level. That almost seems like a feedback loop to me, but it sure doesn't sound like feedback. And since the audio part of the A/V output from the camera doesn't ever connect in any way back to the board, and there's no other input connected to the camera other than the board, then I can't see how a feedback loop could happen anyway. But it seems odd that it starts low and builds, rather than just instantly being at its maximum loudness.
 
Ok, good. So you've eliminated a lot of things and can now focus on the mixer. I assume on step 5, nothing was connected to the inputs and the faders were down. Is that correct? You need to continue to isolate to see if just hooking up the mixer causes the issue.
If that is correct, take the mixer out of the equation. Plug one of the microphones directly into the output cable of the mixer. i.e. microphone directly into the camera, but use the splitter cable. Does it make noise?

Can you replace the mixer with another one? Any mixer that is AC powered will do. I want to know if the mixer creates a ground loop or is making the noise itself. If you replace it with another mixer and it does not make noise, there's your problem. If you replace it with another mixer and it does make noise, then it is most likely a ground loop. Actually, it doesn't even need to be a mixer. Any AC powered audio device with an output that you can connect to the camera should do the job. But a mixer would be best.


No, that's not feedback. The ground loop would be the AC connection. Is the camera AC powered or battery powered? If AC powered, try running it on battery.

If you are running out of time, just buy a ground loop isolator. There are all kinds. Some for the AC line and some for the audio cable. The audio cable isolator is a small investment. It may not fix it, but it won't be a lot of money.
http://www.newegg.com/Product/Produ..._-AT+-+Car+Electronics+Accessories-_-82184650
 
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Paul F said:
Ok, good. So you've eliminated a lot of things and can now focus on the mixer. I assume on step 5, nothing was connected to the inputs and the faders were down. Is that correct? You need to continue to isolate to see if just hooking up the mixer causes the issue.
If that is correct, take the mixer out of the equation. Plug one of the microphones directly into the output cable of the mixer. i.e. microphone directly into the camera, but use the splitter cable. Does it make noise?

Can you replace the mixer with another one? Any mixer that is AC powered will do. I want to know if the mixer creates a ground loop or is making the noise itself. If you replace it with another mixer and it does not make noise, there's your problem. If you replace it with another mixer and it does make noise, then it is most likely a ground loop. Actually, it doesn't even need to be a mixer. Any AC powered audio device with an output that you can connect to the camera should do the job. But a mixer would be best.


No, that's not feedback. The ground loop would be the AC connection. Is the camera AC powered or battery powered? If AC powered, try running it on battery.

If you are running out of time, just buy a ground loop isolator. There are all kinds. Some for the AC line and some for the audio cable. The audio cable isolator is a small investment. It may not fix it, but it won't be a lot of money.
http://www.newegg.com/Product/Produ..._-AT+-+Car+Electronics+Accessories-_-82184650
Click to expand...

The mics are, as far as I know, all XLR connectors, with the exception perhaps of the wireless. I'll have to investigate that. The R500 won't accept an XLR, so there's no realistic way to connect the mics directly to the camera.

I don't have access to another mixer, so swapping out mixers is not doable at this point.

On step 5, nothing connected the camera to the mixer, so it wouldn't matter whether the faders were down or not.

The camera they use is AC powered, but when I took mine there to test it, I ran it only on battery -- same problem.

I'll see if I can get a ground loop isolator before Sunday.

EDIT: Nobody has a ground loop isolator in stock locally.

I appreciate all the help. I really do!
 
I re-read your steps. On step 3 you said you have a buzz with just the mixing board cable connected. But in step 5 you pulled the splitter cable from the board and had no buzz. I thought the splitter cable was the mixing board cable. So now I am confused. A diagram would help.
 
That is an extraordinarily bad power mains HUM/BUZZ in the audio.

Thank you for posting the actual samples. Until you learn the proper names for audio problems,
it is MUCH better to simply post a sample and let us hear it directly instead of trying to describe it.

My very first thought after hearing it for a fraction of a second: How are you POWERING that camcorder?
Is it running on a battery? Are you powering it from a mains-powered wall-wart?
If you are powering it from a mains-powered gadget, what happens if you try to run it from the battery alone?

A bad power mains hum/buzz like that is almost always the result of a ground loop, or a faulty connector/cable.
Or improper interconnection in the first place, but I am rather discounting that as you claim it worked properly before.

That is NOT any kind of signal level (mic/line) issue.
It is also NOT anything to do with any of the INPUTS/sources INTO the mixing console.
It is a function of whatever stuff you have between the output of the mixer and the camera (and whatever is downstream from the camera).

You really need to make a detailed diagram of the whole audio (and video) wiring paths.
Include EXACT make and model numbers of the gear and the exact label of all the connections.
Many of your descriptions are vague and subject to various interperetations.
And you rather hand-wave over details that may not seem important to you, but they are.

As Paul F said, it is time to learn some trouble-shooting skills. Divide and conquer.
You've got so much stuff kludged together it is a miracle that it ever worked properly.

And if you aren't going to properly MONITOR the audio and video, there is almost no point in even attempting to record it.
I've been hanging around these forums for decades, and I regret to say that I have declining sympathy for people who didn't monitor while recording.
 
Paul F said:
I re-read your steps. On step 3 you said you have a buzz with just the mixing board cable connected. But in step 5 you pulled the splitter cable from the board and had no buzz. I thought the splitter cable was the mixing board cable. So now I am confused. A diagram would help.
Click to expand...


What I should have said is with only the cable connected from the mixer to the camera -- that is, without the cable connected from the camera to the DVD recorder -- I still get the buzz. Basically, I get the buzz whenever the mixer is connected to the mic input on the camera, regardless of whether or not anything else is connected to the camera.
 
Richard Crowley said:
That is an extraordinarily bad power mains HUM/BUZZ in the audio.

Thank you for posting the actual samples. Until you learn the proper names for audio problems,
it is MUCH better to simply post a sample and let us hear it directly instead of trying to describe it.

My very first thought after hearing it for a fraction of a second: How are you POWERING that camcorder?
Is it running on a battery? Are you powering it from a mains-powered wall-wart?
If you are powering it from a mains-powered gadget, what happens if you try to run it from the battery alone?

A bad power mains hum/buzz like that is almost always the result of a ground loop, or a faulty connector/cable.
Or improper interconnection in the first place, but I am rather discounting that as you claim it worked properly before.

That is NOT any kind of signal level (mic/line) issue.
It is also NOT anything to do with any of the INPUTS/sources INTO the mixing console.
It is a function of whatever stuff you have between the output of the mixer and the camera (and whatever is downstream from the camera).

You really need to make a detailed diagram of the whole audio (and video) wiring paths.
Include EXACT make and model numbers of the gear and the exact label of all the connections.
Many of your descriptions are vague and subject to various interperetations.
And you rather hand-wave over details that may not seem important to you, but they are.

As Paul F said, it is time to learn some trouble-shooting skills. Divide and conquer.
You've got so much stuff kludged together it is a miracle that it ever worked properly.

And if you aren't going to properly MONITOR the audio and video, there is almost no point in even attempting to record it.
I've been hanging around these forums for decades, and I regret to say that I have declining sympathy for people who didn't monitor while recording.
Click to expand...

I can determine what the cables connect to, as far as mics and such, but the mixer is at the back of the church and much of what connects to it is at the front. It would take a long time to trace each cable to its source, although ultimately that may have to be done.

As I've said, I get the same sound whether the camera is powered by AC or battery, so it's not the AC adapter of the camera causing the problem. I can unplug the other AC adapters -- all of them -- and see if the buzz goes away. All except for the one running the mixer, of course. If the buzz disappears, then I can re-connect the AC adapters one by one until I find the one causing the problem.

If I do isolate it to a single AC adapter, I'm not sure what I can do about it. Most likely whatever that adapter powers is necessary for the service. But I'll cross that bridge when I come to it.

All due respect, but I learned troubleshooting skills while working tech support for Microsoft and IBM. This is just a kluged system thrown together over the years by someone I don't know, so I've been hesitant to rip into it too much, especially since I'm still in 'training' to take over this position -- though neither of the other two guys who have been doing it for awhile seem to care enough about the problem to bother coming and trying to fix it. So that leaves me.

And I totally agree we should be "properly MONITORING" the audio. That hasn't been done prior to my coming on-board, but as a wedding videographer and filmmaker I certainly do understand the importance of it. And monitoring WILL be done from this point forward.

I appreciate your response despite your 'declining sympathy'.
 
Here is a more doable test. Unplug all of the cables going into the mixer so that you only have the mixer and the camera connected. If that solves it then the problem is probably one of the inputs and you can try one after the other till you find the problem one.

The essence of your problem is that the grounding on the audio side has failed. That is either because something isn't grounded or the ground has formed a loop or you have a really big RF field some audio cable is passing through.

The first is usually a broken wire in a connector, or a bad or dirty jack. Usually you would hear other problems with this like crackling and popping so I doubt this is your problem.

For a ground to work everything has to go to one common ground point. What can happen with a bunch of equipment is that you end up having more than one ground point. That creates a loop and the loop acts like an antenna. Now you had an interesting clue with the long build up. I suspect that your loop is a big one. So what that could be is some AC powered device at the front of house that is plugged into one of the inputs to the mixer. That would give you a really big loop and a big loop might take a while to start resonating. I'll bet somebody plugged in a CD player or something down in the front for some event and that is your problem.

The third option also doesn't sound like your problem but FYI if you lay audio cables close to noisy power cables you can pick up hums even with a working ground. You don't see this too often with regular house power but in theatres when you have a lot of power running and you are dimming lights and such you can pick up hums. In this case it is a sharper sound because of the chopped waveform of dimmed AC power. It sounds like yours except it is much more "buzz like" than hum like.
 
I was referring to ONLY the wiring between the OUTPUT of the MIXER and the INPUT of the CAMERA.
The rest of the wiring (everything from the front of the church into the mixer) is IRRELEVANT.
Assuming that the signal out of your mixer is clean by itself.
If the audio coming OUT of the mixer has that buzz/hash, then that is a very DIFFERENT problem and has nothing to do with the camera.


Jumping to solution-space (before we have actually isolated and identified the actual problem),
the remedy could be as simple as a proper isolation transformer. For example...

http://www.radioshack.com/ground-loop-isolator/2700054.html
 
I heard some pretty horrendous noise coming from audio cables (especially unbalanced) when in close proximity to a wall wart or line lump (AC > DC power supply/transformer) So that should be looked into.
As Scott suggested, I would also recommend unplugging everything from the mixer. Then reconnect cables one-at-a-time starting with the mixer > camera, then the other device interconnects leaving the inputs from the stage to last. when noise starts... there's your problem. Since your not interested in giving us detailed info, good luck.
 
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