Mixers/Consoles Noisy A&H GL2400?

[FMEng]

Re: Noisy A&H GL2400

Actually it's the oposite we are driving them moderately high.

Here's one more piece in favor of grounding issues. I have a PC purchased from Stage Research setup for SFX. This sends signal out trhough an Echo Layla then to the GL2400. With the computer (and Layla) turned off and the computer input channel's silenced and muted. If you PFL the line that the computer comes in on, there is a low frequency hum. All other channels when PFL'ed produce a hiss when you get the head phones up around 80% or so.

Grounding issues result in hums and buzzes. More specifically, ground loops cause hums. Shielding problems cause buzzes. Gain structure issues generally result in white-ish noise. Every console will produce some white noise if you look hard enough for it. That's normal.

Can you listen to the noise in the video booth and describe what it sounds like? That's key to finding the solution.

As for some comments made by others, any reasonably designed audio equipment, such as that described here, does NOT need a UPS or other AC surge and noise suppressor to produce clean audio. The idea that those items would help under normal circumstances is just marketing hype. There are good reasons to use them, but cleaner audio isn't one of them.

It always boils down to proper grounding and shielding. Just because the plug fits, doesn't mean it's wired the right way. In a fairly complex system, which probably mixes balanced and un-balanced lines over long distances, you have to know what the input or output circuit is behind the connector in order to wire them together in the best way. In many cases you have to drop the shield at one end to avoid ground loops.

 

[gafftaper]

Re: Noisy A&H GL2400

Here's an interesting twist. I'm running SFX through a small lunch box computer built by the folks at Stage Research. I've got an 8 channel Echo Layla G3 sending the sound through a short Hosa snake and into 8 channels on my GL2400. So For this current show I'm running sound on three buses inside SFX or outputs 1-3 on the Layla. I discovered a lot of hiss coming out of the two speakers fed by bus/output1 from the computer. I switched over to mono using bus/output 2 and it went silent. If I go into the computer and call up the Layla's mixer. The meter on bus 1 shows a lot of random white noise while the 7 other buses are silent. Over on the board if I PFL the 8 channels coming in from the Layla/SFX some are silent while others have a low deep hum.

Could the computer be the source of all my noise going into the system, even though it was muted?

Sorry about the constant speculation instead of troubleshooting it myself. I know very little about jacking into the DSP and I'm afraid if I do I'll screw something up. Plus I wouldn't know where to look to find those meters anyway. Plus I'm not a vidiot and haven't been trained on how to run the video rack so I don't know how to go fire up stuff to see what turns up on the video meters. So I'm doing a lot of speculation in the dark. trying to figure out what to try the next time the video guy comes over to work.

 

[gpforet]

Re: Noisy A&H GL2400

I have had this problem with hum. Running a laptop connecting to mixer. When I'd run the laptop off the plug-in power supply....HUM. When I'd run the laptop off it's batteries....NO HUM. Connected the laptop thru a direct box with ground lift.....NO HUM.

Here's an interesting twist. I'm running SFX through a small lunch box computer built by the folks at Stage Research. I've got an 8 channel Echo Layla G3 sending the sound through a short Hosa snake and into 8 channels on my GL2400. So For this current show I'm running sound on three buses inside SFX or outputs 1-3 on the Layla. I discovered a lot of hiss coming out of the two speakers fed by bus/output1 from the computer. I switched over to mono using bus/output 2 and it went silent. If I go into the computer and call up the Layla's mixer. The meter on bus 1 shows a lot of random white noise while the 7 other buses are silent. Over on the board if I PFL the 8 channels coming in from the Layla/SFX some are silent while others have a low deep hum.

Could the computer be the source of all my noise going into the system, even though it was muted?

Sorry about the constant speculation instead of troubleshooting it myself. I know very little about jacking into the DSP and I'm afraid if I do I'll screw something up. Plus I wouldn't know where to look to find those meters anyway. Plus I'm not a vidiot and haven't been trained on how to run the video rack so I don't know how to go fire up stuff to see what turns up on the video meters. So I'm doing a lot of speculation in the dark. trying to figure out what to try the next time the video guy comes over to work.

 

[Chris15]

Re: Noisy A&H GL2400

Noisy outputs from laptops when plugged in is a fairly normal problem.

Gaff, I hate to state the obvious, but if you yank the plug from the noisy SFX channel, does the whole noise go away? I thought the A&H mute buttons worked, but...

 

[JohnHartman]

Re: Noisy A&H GL2400

I second Chris15s comment, but it seems like you will need the video guy to complete the troubleshooting on this.

 

[gafftaper]

Re: Noisy A&H GL2400

I second Chris15s comment, but it seems like you will need the video guy to complete the troubleshooting on this.

Oh Yeah. I'm trying to build a list of things to try the next time I can get him over.

I've got the computer running directly into the board and just using the line level button up to instead of running through a direct box. Sounds like switching to a direct box with a ground lift is going to be the first thing on my list. Someone mentioned running a laptop off of battery power. Any other suggested tricks for quieting a desktop computer?

 

[Morpheus]

Re: Noisy A&H GL2400

Oh Yeah. I'm trying to build a list of things to try the next time I can get him over.

I've got the computer running directly into the board and just using the line level button up to instead of running through a direct box. Sounds like switching to a direct box with a ground lift is going to be the first thing on my list. Someone mentioned running a laptop off of battery power. Any other suggested tricks for quieting a desktop computer?

.44 magnum?

errrrr......


can you use a ground lifter or isolator? Although, if you use a DI box, that might solve the issue...

Another thing you might want to try is hook a headphone system and check each of your out puts individually.

 

[avkid]

Re: Noisy A&H GL2400

I've got the computer running directly into the board and just using the line level button up to instead of running through a direct box. Sounds like switching to a direct box with a ground lift is going to be the first thing on my list.

I suggest you use a Whirlwind pcDI.

 

[JohnHartman]

Re: Noisy A&H GL2400

Oh Yeah. I'm trying to build a list of things to try the next time I can get him over.

I've got the computer running directly into the board and just using the line level button up to instead of running through a direct box. Sounds like switching to a direct box with a ground lift is going to be the first thing on my list. Someone mentioned running a laptop off of battery power. Any other suggested tricks for quieting a desktop computer?

You can also look at an outboard audio driver usb - audio if is seems that the audio signal out on the laptop is a problem, They tend to be the cheapest designs out there. Also I know this is a dell issue, make sure you are using the correct grounded(3 pin) or ungrounded(2 pin) powersupply for the laptop it was an issue with some of their 630 line of laptops, and I do not know what others that may have impacted.

Main things with the computer is the obvious, make sure you are on the same phase of power, run the audio lines clean and run an audio DI box when ever possible, now I don't run a di box at my theatre, but my laptop is right next to the soundboard and I do not have any issues, but would get mine out if there were any indication of issues.

 

[Anonymous067]

Re: Noisy A&H GL2400

I suggest you use a Whirlwind pcDI.

as usual... .

 

[Chris15]

Re: Noisy A&H GL2400

Let's remember that Gaff does NOT have a laptop, it's a desktop and it's one with an external audio interface of some quality. Grounding could still be an issue.

If you are using line inputs, the correct tool is not a DI box, but an isolation transformer, you don't need the impedance matching that a DI gives if you are playing with line level...

 

[museav]

Re: Noisy A&H GL2400

Gaff, I'd like to go back to your original post.

We have installed a new video system and we have discovered lots of background noise. You can't hear it in the house, but my video guy is complaining about all the noise. Turns out my two year old GL2400 is putting out about 30db of noise with everything off. Is this typical? Is there anything that can be done?

It sounds like nothing changed other than adding the feeds to the video system via the second Audia which ties to the first via Cobranet. Is that correct? And apparently the video feed is noisy and you saw the noise at the Biamp EXPI inputs that went away when you pulled the mixer connections, but you say that you do not hear the noise in the house. Is that correct?

I'm just trying to figure out what really changed. If the house system has no noise problems and is fine with the Shure ULX-P wireless systems and the only changes made were adding the video system and that is where all the problems are manifesting, then that suggests focusing on that part of the system. Another possibility is that in reprogramming the Biamp units perhaps some settings and gain structure were inadvertently altered.

.can you use a ground lifter or isolator?

Hopefully you mean lifting audio signal ground, if you were referencing the power safety ground then that's a terrible idea other than as a very temporary troubleshooting test to confirm any ground loop.

 

[gafftaper]

Re: Noisy A&H GL2400

Let's remember that Gaff does NOT have a laptop, it's a desktop and it's one with an external audio interface of some quality. Grounding could still be an issue.

Thanks Chris. I'm not sure where the laptop came from in this discussion. It's a small Shuttle desktop custom built by Stage Research to maximize the potential of their own SFX software. I was told by a couple of friends that SFX can be picky about the hardware it wants to cooperate with, so we purchased the whole system from Stage Research (including the Layla) in order to get the best results. I didn't notice any noise issues for the first year of use. The computer has never been allowed on the internet or had anything installed on it other than some Audacity plug ins. It's stable and happy and I want to keep it that way.

It sounds like nothing changed other than adding the feeds to the video system via the second Audia which ties to the first via Cobranet. Is that correct? And apparently the video feed is noisy and you saw the noise at the Biamp EXPI inputs that went away when you pulled the mixer connections, but you say that you do not hear the noise in the house. Is that correct?

Close Brad. You can hear the noise from the SFX computer in the house. But only on the bus one output of the computer (and as I mentioned in the last post you can see the noise on the computer's internal mixer). For the current show I disconnected bus one and am using other outputs from the computer and things are now quiet. I did not hear noise from the computer before the video rack was installed.

I'm just trying to figure out what really changed. If the house system has no noise problems and is fine with the Shure ULX-P wireless systems and the only changes made were adding the video system and that is where all the problems are manifesting, then that suggests focusing on that part of the system. Another possibility is that in reprogramming the Biamp units perhaps some settings and gain structure were inadvertently altered.

My video guy has always complained about noise even before the video rack was installed. In the "olden days" (last year) he would setup his cameras in the house and I would run a subgroup output directly to his camera. He would always complain about noise although I couldn't hear it in the house. So things have gotten worse as I can now hear noise from the computer in the house. Although everything else sounds quiet. I can hear the noise from the ULX-P's over the headphones, but it's not enough that I can hear it in the house.

As for the possibility of the gain structure getting messed up. That wouldn't surprise me at all. The guys doing the video install have NOT exactly impressed us with their expertise (state lowest bidder contract).

 

[SHARYNF]

Re: Noisy A&H GL2400

Couple of questions:
what are the INPUTS to the Layla (or are you just using it for output)
What is buss one connected to? are you using an internal shuttle cd drive with the Shuttle, is it using its own internal audio card in addition to Layla

I found an interesting problem with using pc's for audio, basically you need to DISCONNECT any internal speaker )you know the cheap 1 inch one typically comes with the pc. For some reason the noise from in the pc gets picked up via the speaker connection. TYPICALLY someone might not know this or have missed it. Might be worth a check. It drove me crazy for a while

On the video side of things, having done a lot of remote video OB type stuff, what I have done is to get a video isolator for each of the video ins and outs

http://www.fullcompass.com/category/Video-Isolators-Transformers.html
This isolates your system from ground problems on the video in and out, And then I have made sure that any of the video/audio combined equipment that is isolated is still on the same power system as your console.

Sharyn

 

[gafftaper]

Thanks Sharyn. I'll check the internal speaker. Seems very likely that's still connected.

I'm not sure about the video isolator. The only connection between Audioworld and Videoland is the two DSP's talking to each other.

 

[museav]

Re: Noisy A&H GL2400

My video guy has always complained about noise even before the video rack was installed. In the "olden days" (last year) he would setup his cameras in the house and I would run a subgroup output directly to his camera. He would always complain about noise although I couldn't hear it in the house. So things have gotten worse as I can now hear noise from the computer in the house. Although everything else sounds quiet. I can hear the noise from the ULX-P's over the headphones, but it's not enough that I can hear it in the house.

As for the possibility of the gain structure getting messed up. That wouldn't surprise me at all. The guys doing the video install have NOT exactly impressed us with their expertise (state lowest bidder contract).

Just sort of thinking out loud (or should that be typing out loud?) here but what input did his camera have? I can envision a definite problem if they were then or are now running your signal into mic inputs. If you have a powered speaker or some other way of audibly monitoring a line level signal it might be interesting to connect that to the video Biamp outputs and see what kind of signal and noise you get.

Can they describe the noise? Is it hiss or hum or buzz? That could provide some hints.

 

[nev23]

Problem found and fixed.....

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