Fixing a buzz in a Behringer audio mixer

[Airlane]

I'm a musician, not any kind of electronics engineer. I've had a Behringer Xenyx Q1002USB audio mixer for a couple of years. I bought it new. From the start, there was an audible buzz from it at all times, although it isn't present in the audio signal. The mixer has a separate mains transformer which doesn't buzz. Is there a relatively obvious reason for this buzz (Behringer is a low-cost company, with all its products made in China)? Is there also a relatively simple solution? I can use a soldering iron.

 

[rjenkinsgb]

I can't find any internal photos of that unit online, so it's guesswork.

A noise from the device could be from an internal switched mode supply; the inductors used in some types can vibrate slightly and that may be audible.

According to the user manual the power supply only provides 15V; and the unit has 48V phantom power for the mic inputs, so I'd guess there is an inverter in there somewhere..

 

[gophert]

A quick google search of your mixer yields lots of software adjustment-based solutions. Apparently an overdriven or oscillating amp...

 

[Airlane]

I can't find any internal photos of that unit online, so it's guesswork.

A noise from the device could be from an internal switched mode supply; the inductors used in some types can vibrate slightly and that may be audible.

According to the user manual the power supply only provides 15V; and the unit has 48V phantom power for the mic inputs, so I'd guess there is an inverter in there somewhere..

Thanks, that's useful. This is probably more than I am capable of tackling. If I cover the mixer with a thick towel, I can't hear the buzz, so I'll stick that that! It's a problem only because it's installed at home in my quiet living room.

 

[Airlane]

A quick google search of your mixer yields lots of software adjustment-based solutions. Apparently an overdriven or oscillating amp...

Thanks. That seems to be related to noise in the output stage. My mixer buzzes audibly. I'll cover it with a thick towel, which masks the noise.

 

[Nigel Goodwin]

Thanks. That seems to be related to noise in the output stage. My mixer buzzes audibly. I'll cover it with a thick towel, which masks the noise.

Historically mechanical 'buzzing' noises are almost always down to inductors and transformers (noise from the windings), and as suggested it could well be an inverter transformer in the mixer.

If you can get it to pieces, look round for any transformers or coils, and you can identify which one it is by using a long screwdriver as a stethoscope.

Common 'fixes' for noisy coils were to soak them in wax or varnish.

 

[Airlane]

If you can get it to pieces, look round for any transformers or coils, and you can identify which one it is by using a long screwdriver as a stethoscope.

Common 'fixes' for noisy coils were to soak them in wax or varnish.

I'd never have known any of this. Thank you.

 

[Nigel Goodwin]

I'd never have known any of this. Thank you.

It long predates me - I imagine it's a pre-WW2 technique?

 

[unclejed613]

Common 'fixes' for noisy coils were to soak them in wax or varnish.

i worked with a tech that came to the USA from Russia.... his technique was to stick toothpicks into the spaces between the coils and the cores when he found the source of the noise.

 

[gophert]

God invented hot glue guns for a reason.

 

[Mickster]

God invented hot glue guns for a reason.

Hot SnotTM has got to be up there with WD40, duct-tape and CA glue, for it's usefulness.
I've also seen heat-shrink used on occasion...