Noisy mixer channel

[DestinationDrumming]

Long shot but you guys have such a wealth of knowledge and experience.

I have a 10/2 mixer and two of the channels are noisy. Low frequency hum being generated even without anything plugged into them and with the gain turned right down. As soon as the slider is moved up the hum becomes more and more noisy. If I turn the LF pot down it does start to go but then I have no bass through the mics.

Any suggestions as to what it could be before I take it to that very expensive repair dude!

[Mediocrefunkybeat]

Get some contact cleaner on the pots, particularly on the gain pots. Sounds like they're dirty - even if the channels are turned down it's possible.

Alternatively, it could be a grounding/earthing issue. Is it the same when you try another power socket? Try using a 'star' formation when all the audio devices requiring power are plugged into the same extension lead.

[eddiehimself]

Get some contact cleaner on the pots, particularly on the gain pots. Sounds like they're dirty - even if the channels are turned down it's possible.

Alternatively, it could be a grounding/earthing issue. Is it the same when you try another power socket? Try using a 'star' formation when all the audio devices requiring power are plugged into the same extension lead.

Sounds like a grounding issue to me. The low frequency noise i'm guessing is about 50hz?

[DestinationDrumming]

Get some contact cleaner on the pots, particularly on the gain pots. Sounds like they're dirty - even if the channels are turned down it's possible.

Alternatively, it could be a grounding/earthing issue. Is it the same when you try another power socket? Try using a 'star' formation when all the audio devices requiring power are plugged into the same extension lead.

Thanks MFB. I'll pick some up tomorrow and clean them just in case. All the audio devices are plugged into the same socket.

Sounds like a grounding issue to me. The low frequency noise i'm guessing is about 50hz?

Thanks EddieHS. Yes, It is a pretty low frequency. Could it just be grounding on the two sliders and not the rest?

[Mediocrefunkybeat]

Could be. It might be that the construction of the channel has meant that some of the board makes contact with the outer casing. Either way, a good old-fashioned clean wouldn't do you any harm.

[DestinationDrumming]

I guess as it's channels 1+2 they are most likely to be used more often and might get more wear. I'll have a look today.
cheers

[spirit]

Its prob a ground issue as mentioned already and you will have to fix that- get a mains conditioner once you have that done- I have a Yamaha 5.1 amp and could always here a hum...so I went to Maplins spent £50 on the mains conditioner....the moment I put the plasma, amp and all my av stuff in- it was outstanding! The picture was good- its a Pioneer plasma, but man it lept out at me, more vivid and sharper, the sound is crystal clear from the amp also, no background low level hum any more!
Many companys make them and some are very expensive- monster cable seem to be the most available ones in the uk at around £120!!!!!
The Maplins one is brilliant and works so well for half the price- it allows 5 outputs and is about a metre with cable.
Now I have another one for my music pc and work pc too.

[Mediocrefunkybeat]

The mains conditioner sounds like a great idea. I occasionally get hums from my amp not entirely liking my audio interface (I only ever use one or the other mind) and I've solved most of the problem by using the age-old star distribution system. It does work, but there's still some residual background. I suspect my Uni room has something to do with it (the light flickers, for instance) but the conditioner does sound like a good idea.

[larryace]

It's humming because it doesn't know the words.

[eddiehimself]

Its prob a ground issue as mentioned already and you will have to fix that- get a mains conditioner once you have that done- I have a Yamaha 5.1 amp and could always here a hum...so I went to Maplins spent £50 on the mains conditioner....the moment I put the plasma, amp and all my av stuff in- it was outstanding! The picture was good- its a Pioneer plasma, but man it lept out at me, more vivid and sharper, the sound is crystal clear from the amp also, no background low level hum any more!
Many companys make them and some are very expensive- monster cable seem to be the most available ones in the uk at around £120!!!!!
The Maplins one is brilliant and works so well for half the price- it allows 5 outputs and is about a metre with cable.
Now I have another one for my music pc and work pc too.

i'll have to have a look at one of these myself. Thanks mate.

[georgeman]

Try unloading your breaker instead of moving your equipment. Just go around the room and unplug everything on the same breaker.

and what is a star formation?

-georgeman

[larryace]

Try unloading your breaker instead of moving your equipment. Just go around the room and unplug everything on the same breaker.

and what is a star formation?

-georgeman

Unless the breaker trips, it is handling the load. Take it from an electrician who knows. It is a good idea however to plug into a circuit that does not have inductive loads, like motors or transformers (fluorescent lights) on it, just for good measure. So I guess unplugging any refrigerators, air conditioners, fans, or fluorescent lights on the circuit couldn't hurt, so your advice isn't bad advice. A regular incandescent light bulb or any other purely resistive load will not cause any adverse effects, and need not be unplugged.
Also dimmers can be a problem, but it wouldn't manifest itself on just 2 channels, unless there is a specific problem with those 2 channels, which sounds like the case, barring any cord issues.
A star pattern is where you plug all your audio equipment into only 1 power strip, so the grounding potential, and supplied voltage is equal among your various audio components.
A power conditioner is also a good idea, to make sure your audio equipment is recieving a smooth sine wave at a non fluctuating voltage
But as long as you plug everything into outlets that are on the same circuit, (assuming good connections on every outlet) there really is no need for the star configuration. Patch cords, mic cords, and every other component in the signal chain all have to be verified hum free first before accusing your mixer.

[Mediocrefunkybeat]

But as long as you plug everything into outlets that are on the same circuit, (assuming good connections on every outlet) there really is no need for the star configuration. Patch cords, mic cords, and every other component in the signal chain all have to be verified hum free first before accusing your mixer.

Good advice. But I do honestly wonder how many people have 'good' wiring. My parents' house is over 100 years old and the wiring, whilst relatively recent in comparison, can still be sketchy. The same is true of my room at Uni - even though that's only two or three years old, I don't really trust the supply. I do honestly wonder how many homes have truly 'good' wiring and even supplies.

[Deathmetalconga]

This is going to sound weird, but do you have any dimmer switches on the circuit? I was having this problem once and the sound varied according to the position of the dimmer switch. When I plugged into an outlet on a different circuit, I had no problem. When I replaced the dimmer with a standard switch, the problem ended.

[larryace]

I do honestly wonder how many homes have truly 'good' wiring and even supplies.

An incandescent lightbulb is an excellent measure of incoming voltage, if it dims and/or brightens, it means fluctuating voltage. (It will normally dim if a big load turns on, like an air conditioner. Unavoidable. The effect is similar to when someone flushes the toilet, and the shower pressure dips. Voltage is electrical pressure) Good grounding is not as readily identifiable, the whole grounding system has to be verified at the service first, then hopefully the branch circuit wiring doesn't have any crap splices or connections.

I had a real problem with my home security system sending radio signals that every piece of electronic gear in my house would pick up, TV's phones, radios, and my recorder. That took a while to figure out. I had to scrap a lot of tracks because of that thing. One day before a particularly important session, I literally cut every wire going to the unit, tore it off the wall, unhooked the battery and submerged the entire unit in water.

[spirit]

The mains conditioner sounds like a great idea. I occasionally get hums from my amp not entirely liking my audio interface (I only ever use one or the other mind) and I've solved most of the problem by using the age-old star distribution system. It does work, but there's still some residual background. I suspect my Uni room has something to do with it (the light flickers, for instance) but the conditioner does sound like a good idea.

Get it mate- thank me latter! Once you have one you will consider it as important as having decent cans, or speakers- it really is an audio upgrade in itself!

[Mediocrefunkybeat]

An incandescent lightbulb is an excellent measure of incoming voltage, if it dims and/or brightens, it means fluctuating voltage. (It will normally dim if a big load turns on, like an air conditioner. Unavoidable. The effect is similar to when someone flushes the toilet, and the shower pressure dips. Voltage is electrical pressure) Good grounding is not as readily identifiable, the whole grounding system has to be verified at the service first, then hopefully the branch circuit wiring doesn't have any crap splices or connections.



What you're saying makes perfect sense. There are 80-odd en-suite rooms in my building, so some flickering is to be expected, it's just ALL THE TIME. Drives me up the wall, but I completely understand the water analogies. I see them all the time in my course (Music Technology, explaining impedence and resistance to someone is nigh-on-impossible without a water analogy!).

Get it mate- thank me latter! Once you have one you will consider it as important as having decent cans, or speakers- it really is an audio upgrade in itself!

Just a matter of money mate. And finding a Maplin. I think there's one in Preston...

[eddiehimself]

Just a matter of money mate. And finding a Maplin. I think there's one in Preston...

looked on the internet and i found a 6 way power conditioner they're selling for £30. You can get it even cheaper on other websites. Trouble is it's only a 2m cable. Guess i'll have to move the PC over there...

[DestinationDrumming]

Also dimmers can be a problem, but it wouldn't manifest itself on just 2 channels, unless there is a specific problem with those 2 channels, which sounds like the case, barring any cord issues.
Patch cords, mic cords, and every other component in the signal chain all have to be verified hum free first before accusing your mixer.

Yes, juts those two and without anything plugged in. I thought it was a mic lead but the hum is still there without it plugged in.

This is going to sound weird, but do you have any dimmer switches on the circuit? I was having this problem once and the sound varied according to the position of the dimmer switch. When I plugged into an outlet on a different circuit, I had no problem. When I replaced the dimmer with a standard switch, the problem ended.

No, no dimmer switches. The problem is that we live in a single story house so all the sockets barring the kitchen are on the same circuit...could be any of them. Luckily it's only on the two channels so I guess the problem is in the mixer

And finding a Maplin. I think there's one in Preston...

Yep, Round the corner from the street the New Brittania pub is on. Can't remember the name. It was nearly ten years ago that I lived in Preston so i guess I'm excused.

Thanks all for your help

[Mediocrefunkybeat]

Yep, Round the corner from the street the New Brittania pub is on. Can't remember the name. It was nearly ten years ago that I lived in Preston so i guess I'm excused.


Cheers for that. When I make my next set of leads or need some other gubbins, I'll know where it is...!

[larryace]

Gubbins, Maplin...Must be a UK thing. Cause I have no idea what you're referring to ha ha