a Nice crackling noise

[jamesperrett]

When you sent the desk off to be repaired did you send the power supply too (or does it have an internal PSU)? It certainly sounds like a bad connection somewhere in the power supply chain.

 

James.

[Brian]

... they even lost our bog standard hum we have.[/color]

This extra snippet reinforces my thought that your crackle is being induced into your system from outside; it's maybe something like a fridge or a/c unit or even a light fitting.

 

This feels like earthing problems.

[paulears]

Is there any possibility that the desk output has phantom power coming back up the cable?. A couple of years ago, I found a Soundcraft desk behaving very oddly - strange 'signals' on the meters but no output, and odd fizzing and crackles. All that happened was that we'd fed it's output to a small mix wiz to add in some audio from a video unit - and the the mix wiz had phantom turned on, and this, going into master outs, not expecting phantom were producing very strange results. Turning the phantom off cured it straight away. No idea how it was making meters behave strangely.

[PeterD]

The power supply was sent off with the unit along with all the power cables to it that wasn't wired through the wall.

 

how would I find out if it is an external unit?

 

with the phantom power thing I have had the desk running with absoloutly nothing plugged in and all the phantom power switches in the off position. still had the crackle :S

[Bazz339]

Crackling is often indicactive of a poor connection either at mains or low voltage.

 

I would go through all your equipment and all your plug boards, is the equipment PAT tested regualarly? inspecting the plugs, extension and rack sockets ought to be part of that regime. It may be a poorly inserted IEC lead or 13 A plug or a poor connection in any of them. The fuses in some 13A plugs, patrticular in my experience older rubber ones can become badly oxidised and cause a bad connection, in some plugs the fuses are not gripped tightly enough by their holders.

 

Does moving around or moving a piece of equipment ever cause it? Does moving the mains lead to the mixer especially near the plug or where it goes into the mixer produce any crackle? If so that may be the problem or part of it.

 

Are the amplifiers fed from the same location as the mixer? if they are a long way away they may be picking up a different earth, that can cause problems particularly with unbalanced equipment. Is the mains power for the amplfiers on the same phase as the rest of the sound system (You will need input from a qualified electrician if you don't know what I am talking about on that one.

 

I have had at least one desk which had faulty soldering to the buss bars inside, but that is less likely these days.

 

It might be a dodgy signal cable, I have had some that crackled even though the connection was good but that was at mic level.

 

Can the fault be induced by pressing or thumping any part of the desk? I recently installed and Allen & Heath desk which had a dry joint somewhere near the output socket, that sometimes but not always manifested itself on its own as a crackle or when the desk was pushed or gently thumped near the socket. A sharp rap with the nuckles is best, obviously not hard enough to cause any damage. If it does crackle then the fault is likely to be in the desk.

 

Buzzes and hums have a variety of causes including earth loops. Probably the best way to deal with earth loops at line level is some proper balancing transformers with earth lift switches, these are passive so no batteries or power, should be designed to accept a high input signal level which they do not attenuate significantly and often have an earth lift switch that breaks the earth connection in the SIGNAL CABLE. The one thing you should not do in this day and age as you have already been told is disconnect the mains earth to the mixer. If the mixer is quiet with all other items of equipment disconnected then the mixer may be OK but I presume it is an intermiitent fault and therefore often very difficult to find.

 

Good Luck

[PeterD]

Crackling is often indicactive of a poor connection either at mains or low voltage.

 

I would go through all your equipment and all your plug boards, is the equipment PAT tested regualarly? inspecting the plugs, extension and rack sockets ought to be part of that regime. It may be a poorly inserted IEC lead or 13 A plug or a poor connection in any of them. The fuses in some 13A plugs, patrticular in my experience older rubber ones can become badly oxidised and cause a bad connection, in some plugs the fuses are not gripped tightly enough by their holders.

 

Does moving around or moving a piece of equipment ever cause it? Does moving the mains lead to the mixer especially near the plug or where it goes into the mixer produce any crackle? If so that may be the problem or part of it.

 

Are the amplifiers fed from the same location as the mixer? if they are a long way away they may be picking up a different earth, that can cause problems particularly with unbalanced equipment. Is the mains power for the amplfiers on the same phase as the rest of the sound system (You will need input from a qualified electrician if you don't know what I am talking about on that one.

 

I have had at least one desk which had faulty soldering to the buss bars inside, but that is less likely these days.

 

It might be a dodgy signal cable, I have had some that crackled even though the connection was good but that was at mic level.

 

Can the fault be induced by pressing or thumping any part of the desk? I recently installed and Allen & Heath desk which had a dry joint somewhere near the output socket, that sometimes but not always manifested itself on its own as a crackle or when the desk was pushed or gently thumped near the socket. A sharp rap with the nuckles is best, obviously not hard enough to cause any damage. If it does crackle then the fault is likely to be in the desk.

 

Buzzes and hums have a variety of causes including earth loops. Probably the best way to deal with earth loops at line level is some proper balancing transformers with earth lift switches, these are passive so no batteries or power, should be designed to accept a high input signal level which they do not attenuate significantly and often have an earth lift switch that breaks the earth connection in the SIGNAL CABLE. The one thing you should not do in this day and age as you have already been told is disconnect the mains earth to the mixer. If the mixer is quiet with all other items of equipment disconnected then the mixer may be OK but I presume it is an intermiitent fault and therefore often very difficult to find.

 

Good Luck

 

 

 

Yes the PAT testing is done regulaly, and all pieces of equipment were passed. Alot of the equipment is done on IEC leads to Power distributors.

 

It is all on the same phase of power just over 2 switches so that we can only have the amps on for some of our events. are control room is at the back of the room and the amps are on the stage. at least 50m worth of cabling would of been required.

 

I have noticed that, completly by chance, when I leant across the groups the buzz went. could this mean an issue with the group + aux board? this was a definite result as the noise was constant at this point.

 

I have tried a balancing box and that did not work, when using DI's to remove it I started getting issues with mics peaking out when I was trying to run them.

 

with the mixer disconnected from everything the buzz/crackle is still there... but when it was down at the repair center there was nothing at all... it was the quietest I had ever heard the desk!

 

Thanks for all the input

 

Pete

 

 

[Dave SA]

Turn everything in the building on.

 

Then turn everything in the building off one by one other than the desk...

 

Have you moved the desk to the amp rack and plugged it in there? What happened?

[PeterD]

Would running an extension lead to the desk do the same thing as the desk is large and very heavy.

 

I will try the turning everything on one by one.

[Dave SA]

Yes, that would be the same.

[Andrew Edwards]

Sounds like contaminated mains to me.

 

We have all sorts of nuances in our venue. Thermostats, light switches, the hair driers in the salon under the auditorium, even the fire alarm push points repetitive polling when it is really quiet.

Some days are better than others...

[PeterD]

I will be honest I haven't had a chance to try anything yet as I've been on annual leave, but the last post sounds similar... it happens at random intervals etc.... will need to get this all checked really not good for the customers!

[JSalisbury]

I will be honest I haven't had a chance to try anything yet as I've been on annual leave, but the last post sounds similar... it happens at random intervals etc.... will need to get this all checked really not good for the customers!

 

 

Hi,

Can you still hear the crackle and buzz with just headphones plugged into the mixer and NOTHING else connected to the mixer, only mains connected to he mixer?

[PeterD]

 

Hi,

Can you still hear the crackle and buzz with just headphones plugged into the mixer and NOTHING else connected to the mixer, only mains connected to he mixer?

 

Yes