Cleaning up the mains - noisy fridges

[Andy W]

Morning all,

Does anyone have any advice about how to remove an audible click caused by the fridge thermostat kicking in/out? I've looked at a few power conditioners but I'm not entirely sure if they'd do the trick. Or maybe a new fridge?

Any help much appreciated.

Cheers,

A

[ef37a]

Morning all,

Does anyone have any advice about how to remove an audible click caused by the fridge thermostat kicking in/out? I've looked at a few power conditioners but I'm not entirely sure if they'd do the trick. Or maybe a new fridge?

Any help much appreciated.

Cheers,

A

You could try a power "conditioner" but put it on the FRIDGE. But yes, if it is a very old fridge a new one should be better suppressed, tho' mine must be 20yrs old if it's a day and gives me no problems.

Try running your kit from an outlet as near to the consumer unit as possible. Run an extension out to test then if that improves matters seek permission from the distaff side to drill thru' walls.

Dave.

[ryan mead]

You could try a power "conditioner" but put it on the FRIDGE.

Out of curiosity, why?

[ef37a]

You could try a power "conditioner" but put it on the FRIDGE.

Out of curiosity, why?

Because the "spike" is being generated BY the fridge and either travelling back down the mains and into your kit (which SHOULD be proof against such!) or it is being radiated from the mains wiring to the fridge, or a bit of both. If the conditioner does what they claim (and I doubt it frankly!) it should snub the impulse and greatly reduce both modes of propagation.

Have you worked out which piece of audio gear it is getting into and does that have balanced feeds?

I did a HUGE amount of spike and RF suppression work when transistor kit first came out. Mnfcts claimed that a couple of strategically placed Ls and Cs would price them out of global markets. (same happened with moulded mains plugs. "Ooo! CAN'T do that! We shall never be competitive!")

I always groan when some government laccy says "Well, we would rather try a Code of Practice before rushing into legislation" BLLX! Nobody in industry ever does jack till they are pushed!

Dave.

[Andy W]

Many thanks for the replies and advice. The click is audible when monitoring through speakers, and with headphones direct from the soundcard (power amp unplugged). The kit is a 2011 Macbook Pro with RME Babyface. I have a mains filter on the plug feeding the 4 way that the laptop/kit is plugged into, (plus the 4 way has surge protection) and another mains filter on the plug for the laptop itself. I can also hear the click when I'm using another laptop downstairs which has powered speakers plugged into it.

Also I have balanced leads from the soundcard to the power amp - in fact most of the audio wiring is balanced.

Thanks again.

[ef37a]

Many thanks for the replies and advice. The click is audible when monitoring through speakers, and with headphones direct from the soundcard (power amp unplugged). The kit is a 2011 Macbook Pro with RME Babyface. I have a mains filter on the plug feeding the 4 way that the laptop/kit is plugged into, (plus the 4 way has surge protection) and another mains filter on the plug for the laptop itself. I can also hear the click when I'm using another laptop downstairs which has powered speakers plugged into it.

Also I have balanced leads from the soundcard to the power amp - in fact most of the audio wiring is balanced.

Thanks again.

Just goes to show how bog useless mains conditoners are doesn't it!

It seems your fridge is launcing a pretty heft EM pulse so try one of the filter/suppressor strips on that but it would seem a new appliance might be your only recourse.

You could of course turn the fridge off for the duration? If like my son you work mostly in the wee smalls, nothing will spoil if the door is left shut for hours,but you will have to come up with a foolproof warning system to turn it back on before pitting.

Mods: Why can i not see what I am typing at the bottom of this post? This happens at STUDIO-CENTRAL but only just started here'

Dave

[artifus]

...but you will have to come up with a foolproof warning system to turn it back on before pitting.

ha! in my old place there was a post it note that lived semi permanently on the monitor that simply read "fluffing fridge!" or words to that effect.

[Martin Walker]

Because the "spike" is being generated BY the fridge and either travelling back down the mains and into your kit (which SHOULD be proof against such!) or it is being radiated from the mains wiring to the fridge, or a bit of both.

Exactly - if the fridge is creating the spike then suppressing it at source should be far more effective.

Russ Andrews gets a lot of flak on the SOS Forums, but these components from him should do the job if you can't find them cheaper elsewhere:

www.russandrews.com/product.asp?lookup=1&region=UK&currency=GBP&pf_id=5785

Martin

[Yago]

Mods: Why can i not see what I am typing at the bottom of this post? This happens at STUDIO-CENTRAL but only just started here'

Dave

Have to tried CTRL and scroll ?

[ef37a]

Woah! Martin!

Leaving aside your apparent supping with the devil! I do not think it is a good idea to suggest that anyone connect anything into a mains circuit. There is also the risk, small I admit, that people might think that ANY 250V rated capacitor will be suitable (it won't).

Any decent quality "conditioner" that includes the term "surge suppressor" in its spec' should already have these components in it*. One thing the user COULD do if they feel confident about it is chop the mains lead on the conditioner down to the minimum required. I have always felt quite strongly that fitting a 13A PT should be a required skill before you leave school!

*yes, better across the switch I agree.

Dave.

[ef37a]

Mods: Why can i not see what I am typing at the bottom of this post? This happens at STUDIO-CENTRAL but only just started here'

Dave

Have to tried CTRL and scroll ?

Thanks Yago,
No but I will. But why should I have to? (not knocking Jen' jus arrrskin'!)

Ooo!Just makes everthing smaller!

Dave.

[Yago]

Mods: Why can i not see what I am typing at the bottom of this post? This happens at STUDIO-CENTRAL but only just started here'

Dave

Have to tried CTRL and scroll ?

Thanks Yago,
No but I will. But why should I have to? (not knocking Jen' jus arrrskin'!)

Ooo!Just makes everthing smaller!

Dave.

I was having a laugh Dave , last time I recommended that it sent your PC screwy

[shufflebeat]

You could of course turn the fridge off for the duration? If like my son you work mostly in the wee smalls, nothing will spoil if the door is left shut for hours,but you will have to come up with a foolproof warning system to turn it back on before pitting.
Dave

Bog standard timer switch on the fridge before beginning recording? (Remove it for normal use if necessary).

[Folderol]

You could of course turn the fridge off for the duration? If like my son you work mostly in the wee smalls, nothing will spoil if the door is left shut for hours,but you will have to come up with a foolproof warning system to turn it back on before pitting.
Dave

Bog standard timer switch on the fridge before beginning recording? (Remove it for normal use if necessary).

I'd go along with this simple crude solutions are often more practical than the sophisticated stuff

Another note on caps across the mains. Not only are ordinary caps not suited to having their plates squeezed by real power, so will likely have a short life before going bang, but you could find yourself in the unfortunate position of making the whole system resonant at some frequency kicked out as the internal stat switches. This could make the problem much worse and could do some real damage (apart from the cap going bang again). Filter caps always have a resistor with them to protect against this (often built in) so you'd see something like 100n+470R 300VAC.

Incidentally in the old valve TV days almost all mains filter caps were rated at 1000VDC - we usually replaced them with 1500VDC.

Something that just might help at a pinch would be a varistor placed directly across the motor terminals - a bit counter-intuitive but it's the inductance of the motor that produces the spike.

One of these maybe:
http://uk.rs-online.com/web/p/varistor/7118136/

but needs to be fitted by someone who knows what they are doing!

[dubbmann]

hi,

i had a friend who had this problem, we simply did the 'unplug the bugger' trick and that worked.

btw, i'm not an electrical maven but i always assumed that it was an issue with the sudden current draw causing a voltage drop, not a 'spike' per se. have i got it backwards?

cheers,

d

[Folderol]

hi,

i had a friend who had this problem, we simply did the 'unplug the bugger' trick and that worked.

btw, i'm not an electrical maven but i always assumed that it was an issue with the sudden current draw causing a voltage drop, not a 'spike' per se. have i got it backwards?

cheers,

d

Exactly - simple remedies.

As the contact makes, yes you get a current pulse, but (specifically with a motor) at switch-off you will get a high amplitude back emf, and this is usually far more significant.

P.S.
The absolute worst offenders for this are washing machines with mechanical timers

[ef37a]

Yes D' you have it a bit A'uppards!

A load such as a fridge motor is not going to cause any significant drop in the local supply voltage (unless said supply in in a very poor state, but you would have other problems then)

The problem is actually quite complex but a good part of it is because switches do not work as we think, they bounce. When a switch closes the contacts will bounce away from each other by a fraction of a mm. The magnetic energy stored in the inductance of the motor will cause a high voltage across the switch and an arc will result. Now the very first radio transmitters were spark generators! The lumped inductances and capacitances around the switch will determine the frequencies most strongly radiated and dumped into the mains supply.

Even worse is the fact that the switch can bounce several times taking some mSecs to finally close.
A similar situation happens when the switch opens.

In another field, digital electronics, contact bounce was a PITA and EVERY contact had to have its own "de-bounce" circuit.

Dave.

[tim_obrien]

A fridge will hold it's cold for several days as long as the door stays closed.
(I live in Hurricane Central - Florida - guess how I know...)

Just turn it off before you start your recording
and turn it back on later. Won't hurt anything....

[Hugh Robjohns]

When I was a location TV sound recordist many years back it was standard practice to turn off fridges and the like if they made a lot of acoustic noise when they switched on and off.

However, after one occasion when a colleague forgot to switch it back on afterwards, and the production company received a bill for an entire freezer's worth of thawed food, we developed the technique of placing the crew's car keys in the fridge to make sure that we remembered to turn it back on again before we left!



hugh

[Martin Walker]

Hah, that's an excellent idea Hugh

Martin