Have a bit of a strange one. Did a small pub jam night on Thursday and was using some new (old gear new to me) gear for the first time. Now I had set everything up at home previously and there were no problems, set up at venue and had an awful buzz thru monitors. As I hadn't used me snake at home I suspected that but after swapping the main and monitor returns over it was still the monitors at fault. No buzz through main speakers

When I bypassed my monitor eq (re wired and fed monitors direct form desk) the buzz disappeared but after re rigging at home with snake and eq it's perfectly clear.

Now all my gear at the mix end have external psu's (eq, effx and desk) and my powered speakers, alto ts112 for monitors and rcf 712 for foh are obviously earthed. The altos have a ground lift switch but this made no difference, in fact it made the buzz worse.

I suspect something is wrong with the venue power as I have always had issues whatever I do in the place. Always a bit of a buzz somewhere whatever I'm doing (disco karaoke etc using different gear)

Does this sound possible. I use 3 different sockets for powering everything and the mains and monitors are run off the same sockets.

Any ideas?

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I eat kebabs when i'm sober!

You seem to have a possible culprit in this "monitor eq ". Tell us more about it?

Difficult to offer any specific advice, but running from three different sockets (presumably spread around the place) is a recipe for ground loop hums and buzzes.

hugh

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Technical Editor, Sound On Sound

The eq im using is an alesis meq230. External 9v-ac psu, unbalanced jack and phono ins and outs.

Like i said fire it up at home and no buzz, into the venue and buzz.

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I eat kebabs when i'm sober!

as hugh says, running the power from sockets that are on different sides of the room is not a good idea.

What you should do instead is run a long mains extension along with the multicore to supply power to FOH from the same power socket as your amps are fed from, or a socket next to it.

It might not fix your specific problem, but it can't hurt, and is a good practise that will help minimise earth loops in future

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www.Lozjackson.com

Quote Dave71:

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Like i said fire it up at home and no buzz, into the venue and buzz.

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when your at home testing it do you plug everything into sockets that are next to each other?

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www.Lozjackson.com

Quote Dave71:

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The eq im using is an alesis meq230. External 9v-ac psu, unbalanced jack and phono ins and outs.

Like i said fire it up at home and no buzz, into the venue and buzz.

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Quite possible that the venue lighting is generating nasty buzzes that are getting in to your system via the unbalanced wiring, either through ground loops or direct RF interference.

Hugh

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Technical Editor, Sound On Sound

Hi Dave...3 things.....lights, beer pumps and sockets! Dave

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My head hurts!

When I mix from the stage I have a small 8 channel multicore from the middle of the stage to behind me where the desk or mixer amp is. I use one of the channels as return to monitors connected thusly:

aux 3 and aux 4 to EQ (2 x ts j-j)
EQ to multicore (2 x ts lacks into 1 female XLR)
Both signals travel down one channel of the multicore

Here's the interesting bit:

At the stagebox the signals are separated (male XLR to 2x ts jacks) into an ART dti isolator and from there XLRs go to active monitors.

This was prompted by a situation like the one you describe at a party in a field with a very shitty power supply and a chaotic lighting system. I obviously can't say if this'll work for you but it seems to have done for me.

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

As Bossman says, having a mains extension the same length as your snake means you can always keep everything plugged into the same pair of 13A sockets. Mine is a 40m one, and though it's only 1.5 sq. mm cable it gets enough juice to the mixer; all the amps/active speakers are at the stage end anyway. And even if it doesn't solve this problem for you, it's another step along the path of 'righteousness' and one less thing to worry about.

Hugh's diagnosis of noise being injected into the system somewhere in the unbalanced bits is worth looking into as well. In my admittedly limited experience, the two things that people overlook in live sound is the mains situation described above and using crappy unbalanced leads, especially short ones where it looks as if it doesn't matter too much. But I've had similar problems at times and I can't put my hand on my heart and say I've solved them all logically and methodically; sometimes they just hang around until you change something in the signal chain or go to a venue that doesn't give so much bother.

Thanks for all that. First thing i will try is pulling power for the mixer etc from the same socket as everything on the 'stage'.

Im 99% sure its the venue as even when im dj'ing with a simple rig all on one socket i get a hum, not half as noisey but nasty. Ironically on this occasion its just the monitors and not my foh cabinets but bearing in mind the foh are run directly off the mixer with balanced cable.

sadly as its an unpaid venture (do it for the love of live music, supporting local musicians and free beer of course) i cant justify throwing more cash at he job otherwise a better quality gear would help

Quote turbodave:

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Hi Dave...3 things.....lights, beer pumps and sockets! Dave

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**Solution**

Un-pluggeg....in the dark....cant live without the beer!

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I eat kebabs when i'm sober!

Edited by Dave71 (29/04/12 12:27 PM)

Do you have some kind of socket tester that you use in venues, e.g. this? It's the first thing I do in any pub-type venue before plugging anything in. That'll at least spot common wiring faults in their electrical system.

I've always thought the mains-borne noise idea is a bit of a fallacy - the power supplies in even cheap & nasty kit will filter out any muck imposed on the mains and still supply a clean voltage to the equipment itself.

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There's nothing we can't face... Except for bunnies

Mains borne noise getting in via the mains connection is in fact vanishingly rare (at least in the UK), contrary to what the sellers of various mains filters and surge protectors will tell you.

However, earth loops via the mains leads are anything but, and while modern kit of decent quality usually (but, sadly, not always) has it together WRT balanced IO and doing the right thing with pin one, much of the cheaper stuff is either totally unbalanced or just plain gets it wrong.
This is sad, because (particularly for outputs already on XLR) the incremental cost of doing it right is so close to zero as makes no difference.

Power is seldom the problem, voltages produced by circulating currents in the ground network can be, and sometimes pickup from magnetic, electromagnetic (or even, very rarely) electric fields can be, but the mains itself is very seldom an issue.

Regards, Dan (Whos rigs do NOT hum).

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Audiophiles use phono leads because they are unbalanced people!

Some interesting and very relevant stuff here...

Before I go on a few words of explanation... my Celestion SRs work best with a controller upstream of the amp. This only has unbalanced inputs and outputs so the first few times I used it I was all of a twitter expecting hums and buzzes. (It sits on top of the amp so very short patch-leads between it and the amp. And always common mains supply) But for two years in all sorts of venues all was beautifully silent.

Then last weekend I used a new amp for the first time... BUZZZZZZZZZZ. Time was tight so having one of Mr Behringer's little hum-buster boxes buried in my fix-it box that was quickly patched-in and blissful silence resulted. Haven't had time to investigate further since as to whether it was building mains issues - the building WAS 'venerable'! - or the proximity of several lighting effects or some other site/gig specific 'feature', but you never can tell... always be a boy-scout!

(Interestingly the new amp was a significant upgrade from a respectable bargain-basement job to an 'industry standard'.)

Investigations continue...

Update - slight change of plan

For now I have ditched the cheap and chearful eq and dropped in my redundant driverack px. As the DBx has balanced ins and out I'm hoping it will solve the problem but will find out later on this month

In the meantime I have matched the eq curve that I had my old eq set on which I set at home with mic and my acoustic guitar to weed out feedback but am aware that other guitars feedback in different eq bands. With this in mind I'm thinking of using the AFS ( auto fed back suppression) utility on the DBx to quickly quash any feedback. Hopefully the DBx won't drop many frequencies.

As It's just for open mic/jam nights we have a quick turnaround and various instruments and singers. Normally this wouldn't be such an issue but unless you were there you might not appreciate what I have to contend with. Some want very loud monitors and sit on stools with acoustic guitars very close to monitors, some vocalists hold the mic at waist height when not singing etc etc etc

I appreciateI it's not ideal and when I'm with my band doing stuff we can set and forget as we use the same gear all the time

Cheers

Dave

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I eat kebabs when i'm sober!

Update

Same venue last night and as I had a bit of spare time I rigged up using the old eq with all the power coming off the same socket as suggested above.

Monitors still buzzed badly as before so swapped over to a drive rack and problem resolved. Had to try before the meq went in the bin.

Cheers

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I eat kebabs when i'm sober!

Alesis MEQ?

-it'sunbalanced -ok for monitor EQ on the inserts, but not "straight through"...


>

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planet nine
lincoln, uk.

Sadly we are lacking on the inserts front so straight thru is my only option

Now on the look out for an EQ if anyboady has one laid about. 30 band Dual Channel in a 1u frame ideally, but 2u will be ok

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I eat kebabs when i'm sober!