SOLVED: Audio problem - HELP!

Rick R said:
Since your not interested in giving us detailed info, good luck.
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WTH??? How am I 'not interested' in giving detailed info???? I've told you EVERYTHING I KNOW. And I've admitted my knowledge is LIMITED when it comes to audio issues. The equipment isn't MINE and I don't have access to it 24/7/365. It sits in the sanctuary of my church, which is locked most hours of most days. I have to make arrangements to be able to get in there to test things and make notes. And I wasn't even in TOWN today.

I've SAID that I would try to find out more about what's plugged in and where it goes as soon as I possibly can, which is probably going to be tomorrow morning.

So what's with this snarky attitude???
 
Look folks, I freely admit that my knowledge of audio is extremely limited. That's why I posted the question here, so that people who have the knowledge and experience can help me figure this out.

I have had this situation thrust upon me, and I'm doing my best to try to figure out what's wrong and fix it so that the folks who can't make it to church can still have the service they so keenly desire to see and hear. It's shameful that the people who put this system together don't care enough to try to help me fix the problem, but I can't do anything about that. And the church simply doesn't have the money to pull it all out and replace it with something better and newer. So I'm doing the best I can.

I appreciate ALL of the good advice and information here -- I truly do! Please don't let my lack of knowledge or experience keep you from helping me to help the home-bound parishoners of my church.

Hopefully tomorrow I will have more information, more answers -- and perhaps, thanks to all of you, a solution.

Again, thank you ALL for your help. God bless you!
 
As a general rule the louder the problem the earlier it is in the signal chain. The wrinkle here is that since you are going mic in to the camera you are essentially starting a new audio chain at that point, so even a smallish buz could get amplified a lot. However since the voices are not crazy loud I'm discounting that "chain". It is very unlikely that you picked up that much hum on the jump from the mixer to the camera. It's possible, not not likely. The most likely is that you have a hum coming in on one of the inputs that is then getting amplified by the mixer. That the hum goes down when all the faders are down supports this.

Hum eliminators work by breaking the loop. If you can locate one IN the loop then they are very effective. If they are not in the loop less so. So it's still important to find where the problem is. Long cable runs are prone to hums, but yours is quite loud and I still bet on something plugged in to an input somewhere at the front of house.

These things can take experienced professionals awhile to track down so be patient. The hardest part is to not jump the gun and change a lot of things at once, "fix" the problem but not know what caused it.
 
Interesting tidbits I learned today...

1. With power OFF to the mixer, amp, power conditioner, wireless receiver and wireless transmitter (for the hearing impaired) as well as the DVD recorder, VCR, CD player and the camera itself (running it on battery only), but with the camera still connected to the mixer via the same cable as before, there is NO BUZZ. Of course, there is NO AUDIO going into the camera either, so that's not entirely unexpected.

2. With ALL input and output cables disconnected from the mixer, the buzz level drops from about 75% to about 50%, which is still unacceptable.

3. With ALL AC adapters unplugged from the power strips (x2), and 1 one the power strips unplugged from the other one, the buzz remains at 75%. This includes unplugging the AC adapter for the camera itself.

4. If I disconnect the A/V output cable from the camera, the buzz drops to 50%.

5. If I turn all sliders on mixer to 0, the buzz drops to 50%.

6. If I turn either the #1 slider or the two output level sliders to 0, the buzz drops to 50%. Lowering any other slider has no effect on the buzz level.

7. Taking the splitter out of the mix has no effect on the buzz level. It also appears to be unnecessary, so I replaced it with a mono 1/4" to mono 3.5mm cable running from mixer to camera. Buzz remains. The second side of the splitter was an audio cable running to the right audio input of the DVD recorder. This is unnecessary since sound from the mixer goes through the camera and into the recorder. So I removed this cable and the splitter, which had no effect on the buzz level in the camera.

8. At no point does the buzz register on the volume level LEDs on the mixer itself.

9. In the cabinet beneath the mixer there sits the Peavy XR 600C amp and the Powerwerks 1501C Power Conditioner. I have no feasible way to turn off the amp. Turning off the power conditioner kills power to everything else, same as turning off the master power switch. At this point I have no way to bypass either device to determine the effect on the buzz level.

10. I noticed on the mixer that 'Phantom Power' was turned on. Turned it off -- no effect on buzz level. So I turned it back on.

11. Disconnecting the A/V out cable from the camera causes the buzz level to drop to 50%.

12. With power OFF to all unnecessary devices (VCR, DVD recorder, CD player, wireless receiver, wireless transmitter), the buzz level remains at 75%.

13. The ONLY thing that makes the buzz level drop below 50% is to either power off the mixer or disconnect the cable from the mixer to the camera -- in other words, to cut any and all audio signal from mixer to camera. When this is done, the buzz level drops to 0%, but there is no audio provided to the camera.

So those are today's tests and observations. It may be there is a hardware failure in either the mixer or the power conditioner, or possibly the amp -- the only way I know to test for that is to swap them out with known-good devices, and I have none to swap with.

There are only a few microphone inputs that are used on a regular basis -- the preacher's wireless lapel mic (which is only used briefly at the beginning of the service), the pulpit mic, 2 mics on the choir, and a mic on the piano. Sliders for all other inputs will be kept at 0, although this doesn't seem to improve the buzz problem at all. From time to time we do have soloists who sing or play an instrument, but I'll deal with that when it happens.

The camera portion of the chain is cabled as follows --

1. Mixer in through mic input on camera, via mono audio cable.
2. A/V out from camera to A/V input on VCR.
3. A/V out from VCR to A/V input on DVD recorder. The VCR also outputs via coax to TV's located in classrooms in an adjacent building.
4. Video (only) out from DVD recorder to LCD monitor.

As I said, when I disconnect the A/V out cable from the camera -- removing VCR, DVD recorder and monitor from the audio chain -- it reduces the buzz level to 50%. But that same thing happens when I turn the master outputs on the mixer down to 0. Doing both does not reduce the buzz level below 50%.

So as it stands, I have no solution for this problem. I'll have to record 'wild' sound on tomorrow's service and hope for the best.

Again, I appreciate all of your advice.
 
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While I follow most of your explanation, it would really help to have a diagram so we can follow along and it will be much easier to make suggestions. That would include showing all the AC connections including power strips.
 
Paul F said:
While I follow most of your explanation, it would really help to have a diagram so we can follow along and it will be much easier to make suggestions. That would include showing all the AC connections including power strips.
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Well I'd love to do that, but it's a rat's nest of wires in the cabinet, and most of them run under the floor to other parts of the sanctuary and church. Some of the inputs are labeled so that it's unclear what is connected to them. I can tell you what they're labeled as, but I can't tell you where the cables go, specifically, or what they might run past, on top of, or underneath. I didn't run them, and whoever did isn't around to tell me.

The mixer and amplifier are at the back of the sanctuary. The pulpit mic, choir mics, and piano mic are at the front. When the preacher uses the wireless lapel mic, he is at the front and the receiver is at the back. The CD player hasn't been used or turned on since I've been involved.

The thing is, none of this has changed recently -- none of the cabling has been altered or modified. Nothing has been added to or removed from the system. As far as I know, no other changes to electrical wiring or anything else in the sanctuary have been made. The buzz wasn't there two weeks ago, but it's there now.

All of the wired mics are across the room -- a fAirly large room -- from the mixing board.

But again, even with all inputs and outputs disconnected from the mixer, the buzz is still there. So that would seem to eliminate cables or mics from the equation, and leave us with the components themselves -- mixer, amplifier and power conditioner. Either an internal failure on one of them, or some sort of AC power-related problem.

The preacher did tell me today that one day a week or two ago there was a series of power failures at the church -- it went off and came back on again several times, before going out completely for awhile until the power company restored the power to the area. This could have damaged the equipment and be the cause of the problem. The master power switch to that equipment is supposed to be turned off during the week, but maybe that week it was left on by accident or turned on by someone else at some other time. There's no way to know about that.

The preacher and I are going to go at the problem one day this coming week. We're going to pull out the PA, power it off and disconnect it from the system, to see if that makes the buzz go away. If it does, it may be the PA needs to be replaced. If that doesn't do it, then we'll bypass the power conditioner and see if that's the problem. If neither makes the buzz go away, then it may be the mixer itself needs to be replaced.
 
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It happens that I own the same Soundcraft Spirit Folio 10-2 mixer that the church is using. It's a nice little portable console with really good preamps and quality faders for the price. I use mine mostly for classical, choral and acoustic folk music recording in the field (generally into a recorder, not with video).

But all its outputs are +4 dBu balanced line level on 1/4" TRS jacks. That's a whopping big signal to send to the poor little camcorder with its only input being at mic level. Apparently the Canon has pretty good AGC, because there doesn't appear to be outrageous distortion on the voices. But when they stop speaking, the AGC pumps up the background noise, which might not be so bad if it were attenuated 30 or 40 dB to a more acceptable mic level.

Any PA setup will have a certain level of background hum and noise, but it's usually well below audibility; the problem here is that you're feeding a heavily over-amplified signal to the camcorder, which is seeing the hum as well within the range of microphone level signals it is designed to record.

I think what the OP needs is an attenuating cable to connect the mixer to the camcorder. Unbalanced 1/4" TS to 3.5mm TS ought to be OK; the Soundcraft can feed an unbalanced output just fine.

Or have you tried this already? Did that old splitter by chance have an attenuation switch on it that might have gotten flipped since two weeks ago?

- Greg
 
Greg Smith said:
It happens that I own the same Soundcraft Spirit Folio 10-2 mixer that the church is using. It's a nice little portable console with really good preamps and quality faders for the price. I use mine mostly for classical, choral and acoustic folk music recording in the field (generally into a recorder, not with video).

But all its outputs are +4 dBu balanced line level on 1/4" TRS jacks. That's a whopping big signal to send to the poor little camcorder with its only input being at mic level. Apparently the Canon has pretty good AGC, because there doesn't appear to be outrageous distortion on the voices. But when they stop speaking, the AGC pumps up the background noise, which might not be so bad if it were attenuated 30 or 40 dB to a more acceptable mic level.

Any PA setup will have a certain level of background hum and noise, but it's usually well below audibility; the problem here is that you're feeding a heavily over-amplified signal to the camcorder, which is seeing the hum as well within the range of microphone level signals it is designed to record.

I think what the OP needs is an attenuating cable to connect the mixer to the camcorder. Unbalanced 1/4" TS to 3.5mm TS ought to be OK; the Soundcraft can feed an unbalanced output just fine.

Or have you tried this already? Did that old splitter by chance have an attenuation switch on it that might have gotten flipped since two weeks ago?

- Greg
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Sounds very reasonable and likely. Certainly seems to fit the behavior I'm seeing. The splitter had no switch of any kind and nothing to indicate it attenuated anything. Not even a Radio Shack part number on it, so I can't look it up for specs. But most likely it was just a splitter and nothing more.

I had thought that the fairly slow ramp-up of the noise -- what I've been calling 'buzz' -- seemed like maybe some kind of AGC thing. That certainly sounds plausible. I just wonder why it wasn't a problem before?

There doesn't seem to be any setting in the camera setup menus for turning audio AGC on or off, so I assume it's on permanently. I wonder why an AGC would adjust noise that is such a low level to begin with up to something that's 75% of maximum loudness, though. That seems excessive to me, but I'm no expert.

The only attenuating cable I see on Amazon that seems appropriate is this one -- http://www.amazon.com/gp/product/B0...ue&ref_=ox_sc_act_title_2&smid=A361GUAHDKQL1Q

It would require an adapter on one end to adapt the RCA plug to a 1/4" mono plug, but that's no big problem -- I might even have one in my bag already. Would 60db attenuation eliminate the problem? For less than 4 bucks, it's sure worth a try.

Thanks!
 
Since it used to work, something broke or was re-configured. If you attenuate, all you are doing is the same as pulling the fader down on the master level. It will just make the level of the audio along with the buzz lower.
 
David W. Richardson said:
Well I'd love to do that, but it's a rat's nest of wires in the cabinet.....

All of the wired mics are across the room -- a fAirly large room -- from the mixing board.
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We don't need a complete diagram. Just diagram what you know. That will help the discussion.

A rat's nest and long cable runs are a great way to induce noise. Someone broke a ground or broke a shield on a cable or put a cable next to some strong magnetic field or created a ground loop, or the mixer has gone bad.
 
Paul F said:
Someone broke a ground or broke a shield on a cable or put a cable next to some strong magnetic field or created a ground loop...
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I don't know how that could happen. No one has fiddled with any of the wiring inside the cabinet, and everything outside the cabinet runs under the flooring. Nothing has been modified inside that building in quite a while. Nothing has been introduced into the building in the last few weeks that would create a strong magnetic field.

I'm leaning toward the conclusion that the mixer went bad, probably as a result of power surges during the time when the power at the church went off and back on several times within a minute or so. When the same thing happened at my house a few years back, it corrupted the circuit board on my digitally-controlled water heater, requiring me to replace the board. Now whenever the power even flickers, we flip the breaker on the water heater until things settle down.

I can easily see the same kind of power issues damaging the mixer. It's the only thing that really makes any sense to me at this point. Unfortunately, I don't know any way of testing that theory other than to replace the mixer with a new one. I would hate to have the church spend the money on a new mixer, only to find that that didn't resolve the problem. But there seems to be little alternative.
 
David W. Richardson said:
I had thought that the fairly slow ramp-up of the noise -- what I've been calling 'buzz' -- seemed like maybe some kind of AGC thing. That certainly sounds plausible. I just wonder why it wasn't a problem before?

There doesn't seem to be any setting in the camera setup menus for turning audio AGC on or off, so I assume it's on permanently. I wonder why an AGC would adjust noise that is such a low level to begin with up to something that's 75% of maximum loudness, though. That seems excessive to me, but I'm no expert.

The only attenuating cable I see on Amazon that seems appropriate is this one -- http://www.amazon.com/gp/product/B0...ue&ref_=ox_sc_act_title_2&smid=A361GUAHDKQL1Q

It would require an adapter on one end to adapt the RCA plug to a 1/4" mono plug, but that's no big problem -- I might even have one in my bag already. Would 60db attenuation eliminate the problem? For less than 4 bucks, it's sure worth a try.
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The ramping of the noise is also what got me suspecting AGC involvement. Most small consumer video cameras don't have any way to defeat the AGC -- in fact, at the price of that Canon, it's actually unusual to have an external mic jack at all.

60 dB is a lot of attenuation -- I was thinking more like 30 or 40 dB -- but the cable is cheap and would be worth a try, I think. If it gets you in the ballpark but the level is too low, you might go for a better one; I'd look at Sescom and Markertek as possible sources.

- Greg
 
Paul F said:
If you attenuate, all you are doing is the same as pulling the fader down on the master level. It will just make the level of the audio along with the buzz lower.
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Not entirely true. There is still an output amplifier/buffer stage and possibly a transformer past the master faders. Any noise/hum picked up or generated there wouldn't change with the fader setting.

See the somewhat similar thread about using an attenuating cable with the Tascam DR-70D for an example of a case where this clearly does work.

- Greg
 
I lost the plot. I cannot visualise the wiring at all, I think I have a handle then the next posts confuse me again. It's pretty clear it's a total mess, with 'wires' not being able to be identified or tweaked. Personally, I would draw out the wiring on paper, as I remove everything, and start again. Pages back somebody suggested starting with a clean slate and adding item by item to the mixer until the problem appears. Did this happen? It's critical fault finding stuff. You cannot do it randomly. It needs a clearly established rewire path, so the problem can be diagnosed. If this is beyond your ability, it's fine, and then you need to find somebody to do it for you. We can advise, but the curing is down to you, and you do seem a bit resistant to experiment, just gently tweak, which won't do it, unless pure luck is involved.
 
I can guarantee that if you ask the congregation and your friends that someone will have a mixer you can borrow for a day to test your theory. I suspect it's another problem but one should never assume it's not equipment failure. The reason I doubt it's the problem is that a grounding problem is not a likely result from power surges.
 
wjauch said:
To the OP, are you 100% certain that AGC cannot be turned off? I own an older Canon HF10, audio level can be adjusted manually. The manual of your cam suggests to me that this can also be adjusted on HF R500, on page 143 "control button" Mic level, lists A automatic, and M manual. http://www.okanagan.bc.ca/Assets/De...echnology/et_pdf/Canon+HFR500+user+manual.pdf
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You will notice that manual covers 3 different camera models -- the R50, the R52, and the R500. I assure you, the R500 does not have the 'Control Button' menu option, or any other menu option to control volume level. It has audio 'scenes', but none of them have manual adjustments. I wish they did.
 
This morning before the service began, I was discussing with the other two people who have done this job, the things I had done to try to isolate the problem. The subject came up of replacing things, and I mentioned that the mixer itself could be replaced for less than $300. They both seemed shocked that the cost was much lower than they had assumed. The preacher happened by, and he also was surprised and said maybe they needed to consider replacing things.

After the service, one of the church members came up and said, "If all you need is $300 to fix this, then here." He handed us three $100 bills. When we took them to the treasurer, he told us someone else had also contributed -- so we now have $346 to spend.

The preacher wants us to replace the mixer, so we're ordering the Soundcraft EPM8. It's very similar to what we already have, so the transitional learning curve should be pretty shallow.

Next we want to see what kind of amplifier would be a good replacement for the old Peavey XR600C. Any suggestions?

Neither of these may resolve the hum issue, but it's always good to update equipment. :-)
 
paulears said:
I lost the plot. I cannot visualise the wiring at all, I think I have a handle then the next posts confuse me again. It's pretty clear it's a total mess, with 'wires' not being able to be identified or tweaked. Personally, I would draw out the wiring on paper, as I remove everything, and start again. Pages back somebody suggested starting with a clean slate and adding item by item to the mixer until the problem appears. Did this happen? It's critical fault finding stuff. You cannot do it randomly. It needs a clearly established rewire path, so the problem can be diagnosed. If this is beyond your ability, it's fine, and then you need to find somebody to do it for you. We can advise, but the curing is down to you, and you do seem a bit resistant to experiment, just gently tweak, which won't do it, unless pure luck is involved.
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The only 'clean slate' scenario where the buzz doesn't appear is when either everything including the mixer is powered off or the audio cable from the mixer to the camera is disconnected from either end. In which case there is no signal going to the camera at all. As long as the mixer, amplifier and power conditioner are powered on, there is buzz.

I have disconnected all inputs. I have turned off and unplugged power from all external devices (DVD recorder, VCR, CD player, wireless receiver and wireless transmitter.) The buzz remains. (Since the buzz continues even with all inputs unplugged from the mixer, it doesn't seem that the mics or cabling to the mics are the problem.)

So there is no 'clean slate' point from which I can individually re-add devices or inputs.

This is what leads me to believe that the problem must reside in either the mixer, the amplifier or the power conditioner. This coming week the preacher and I will pull out the amplifier from its place crammed into the cabinet, and power it off.

If that doesn't stop the buzz, then I will power off and bypass the power conditioner.

If that doesn't stop the buzz, then it seems to me that the fault must lie in the mixer itself. Or else there's some other possibility I haven't thought of yet.
 
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