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Combating refrigerator noise

post #1 of 16
10/13/10 at 6:36pm
Thread Starter 

I have an issue with the power quality that's being caused by my small dorm refrigerator (a Sanyo). Every time the compressor starts and stops it sends a rather loud click through my headphones- especially on my McIntosh. The chain of power for all of my audio equipment is as follows:

 

Wall outlet

Tripp Lite ISOBAR6DBS (last/most filtered outlet pair)

TOPAZ Line 2 1kVA power conditioner/isolation transformer

Sub-$5 power strip

Freebie power cables

Equipment

 

The refrigerator:

Same wall outlet

Cyber Power 895

MonoPrice grounded extension

Refrigerator

 

I don't see what I can do beyond investing in some sort of AC-DC-True sinusoidal AC converter but I doubt such a thing exists for a reasonable price (sub $75). Has anyone had this problem and resolved it?


Edited by MCC - 10/13/10 at 6:37pm
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post #2 of 16
10/14/10 at 5:49pm

If its getting through all that power filtering its probably some kind of RFI, not mains contamination.  See if it happens when listening from a portable source.  If it does, its gotta be RFI.

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post #3 of 16
10/14/10 at 6:12pm
AC motors kick off a bunch of RFI. The noise is probably being broadcast as opposed to going through the power lines.

Try shielding the motor, or if possible, put up a metal plate between the fridge and your rig. If there's a wall, you could screw a thin aluminum plate behind it.

Shielded cables might also help, but there's still the possibility that the RFI is getting in somewhere else. RFI is a tricky beast. It's like trying to waterproof something when you can't see the water.
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post #4 of 16
10/14/10 at 6:16pm

well it would certainly help to try moving the refrigerator to another outlet if possible wouldnt it?

 

my solution was to move the refrigerator to another room, but it sounds like you dont have that option

 

you could always just get rid of it ;-)

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post #5 of 16
10/14/10 at 6:16pm

Or if the fridge has stainless steel panels you could ground them.

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post #6 of 16
10/14/10 at 9:34pm
Thread Starter 

All good ideas. I live in a 10"x11.5" cube in an older building with few outlets. My room configuration unfortunately doesn't allow for the refrigerator to be moved without making it difficult to walk around. 

 

I hadn't thought of RFI but I'm willing to bet that's the culprit. The refrigerator is only ~5ft from my rig and the old McIntosh is unbelievably susceptible to interference from my phone. This would also explain why my Harman/Kardon and Headfive aren't affected nearly as much as they're both mostly sealed in metal enclosures.

 

The fridge is indeed steel and is of the newer type that has a mostly enclosed back instead of an exposed radiator. The chassis is already grounded so all I need to complete the faraday cage is a relatively fine metal mesh bent around the compressor area. I doubt I'll be able to solder to the stainless steel even with my 120w soldering gun and radio shack flux so I guess I'll have to try duct tape. 

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post #7 of 16
10/27/10 at 9:42pm

Try an ultimate outlet from PS Audio.  It will filter out all of that noise.  I did an experiment with a friend.  I hooked the UO to one plug on on outlet and then a hair drier to the other.  When I turned the hair drier on, you could not hear it through my speakers.  When the UO was out of the picture, you hear the electrical noise through the speakers.

 

I have a lot of PS Audio's power cleaning stuff.  The best piece of audio gear I have and will never sell is the PS Audio P600 which is a power regenerator.   It takes AC power, converts it to DC, and then outputs it to AC.  The result is a perfect sine wave at a steady voltage.  The power regenerators cost a lot, but the outlets are comparitavely cheaper.
 

Quote:
Originally Posted by MCC View Post

I have an issue with the power quality that's being caused by my small dorm refrigerator (a Sanyo). Every time the compressor starts and stops it sends a rather loud click through my headphones- especially on my McIntosh. The chain of power for all of my audio equipment is as follows:

 

Wall outlet

Tripp Lite ISOBAR6DBS (last/most filtered outlet pair)

TOPAZ Line 2 1kVA power conditioner/isolation transformer

Sub-$5 power strip

Freebie power cables

Equipment

 

The refrigerator:

Same wall outlet

Cyber Power 895

MonoPrice grounded extension

Refrigerator

 

I don't see what I can do beyond investing in some sort of AC-DC-True sinusoidal AC converter but I doubt such a thing exists for a reasonable price (sub $75). Has anyone had this problem and resolved it?

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post #8 of 16
10/27/10 at 10:14pm

http://search.aol.com/aol/search?invocationType=tb50-ff-aolnews-ab-en-us&query=noise+harvesters

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post #9 of 16
10/28/10 at 2:31pm
Thread Starter 

It looks like the ultimate outlet does the same thing as my $25 35lb Line 2. I'm still convinced that the issue is probably with RFI instead of line noise but I haven't yet had the time to get some mesh for the refrigerator.

 

Something like the P600 would indeed be useful for filtering out line noise. I'm just not willing to spend more than $75 on anything involving wall power. Perhaps a DIY project is in order once I get some more EE coursework in.

 

Finally, I'm not sure how exactly the noise harvester is supposed to work. I have a very difficult time buying electronics without first seeing high resolution pictures of the insides and having at least a basic understanding of an item's operating principle.

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post #10 of 16
10/28/10 at 4:24pm

MCC,

 

I think that the Ultimate Outlet goes a little beyond your line 2.  The PS Audio website has info on the ultimate outlet if you've a mind to go there.

 

Not sure about your 'fridge, but I doubt that it's motor is powerful enough to come through your setup.

 

I only mentioned the P600 to build a context for PS Audio's power products.  Also, you might have to spend a little more than $75.00 to filter line noise.

 

My understanding of the noise harvester is that it is different from the Ultimate Outlet.  I have no experience with it, and I know for a fact that the UL will eliminate line noise in the home and at work.

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post #11 of 16
10/29/10 at 9:07am
Quote:
Originally Posted by MCC View Post

Something like the P600 would indeed be useful for filtering out line noise. I'm just not willing to spend more than $75 on anything involving wall power. Perhaps a DIY project is in order once I get some more EE coursework in.

 


First I would try some simple, not too expensive solutions such as this DIY power cable or any power cord with twisted pair and these ferrites:

http://www.radioshack.com/product/index.jsp?productId=2103222

http://www.radioshack.com/product/index.jsp?productId=2103222

 

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post #12 of 16
10/29/10 at 9:26am
Thread Starter 

I don't believe in the capability of premium power cords to deliver 60Hz AC any better than the cheap ones, but I will try snapping a ferrite choke near the entry point of my McIntosh's power cable. I think I have an extra somewhere.

 

I added a safety ground to the McIntosh some months ago by cutting the end off of a standard IEC power cable and tying the end in a knot inside the receiver after removing the original cable. The noise still exists when I cheat the ground (temporarily!) so that isn't the issue. 

 

And yes, the ground is 100% necessary. A couple months ago I accidentally powered the McIntosh on without slowly bringing up the voltage with the variac. The damage was a physically popped open resistor shorting against the chassis and a shorted rectifier diode. I'm unsure if the fuse would have blown without the ground since I don't know which failure occurred first. 

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post #13 of 16
10/29/10 at 2:54pm
I've heart people succesfully combating refrigerator noise and the likes by adding a capacitor across the mains wires of the culprit; very cheap, but being an electronic nitwit I've no idea about the becessary type and values of that cap. Search!
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post #14 of 16
10/29/10 at 9:36pm
Thread Starter 

The Line 2, in addition to containing an absolutely massive transformer, also has a rather large (physically) capacitor directly on both the hot and neutral AC lines. It tests fine on my ESR meter but I haven't tested its capacitance so I don't know for sure if it's doing its job. 

 

It looks very similar to this:

 

30uF_370V_440VAC_CBB65_Running_Capacitor_Round_Oval_Metal_can_Cool_Air_conditi.jpg

 

It's entirely possible that this isn't enough though. I'll definitely keep your suggestion in mind if turning the refrigerator into a Faraday cage doesn't help. I'll probably be able to make it to the hardware store this weekend.

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post #15 of 16
10/31/10 at 11:43am

 

Quote:
Originally Posted by dura View Post

I've heart people succesfully combating refrigerator noise and the likes by adding a capacitor across the mains wires of the culprit; very cheap, but being an electronic nitwit I've no idea about the becessary type and values of that cap. Search!


I've modded the power cord of a Grundig CD 435 (found in a dumpster) this way and it did clean up the sound, so it works both ways. One have to take into account the European grid, I used RIFA PME271M610MR300PS, 275 VAC, 0.1 µF costing me $2.9 and an Eljo plug with room for the cap, costing $3.3. Total cost $6.2, in US I guess it's a lot cheaper.

 

Very easy DIY, no soldering required:

 

PME271M610MR300PS.jpg

 

A refrigerator pulls more, but have tested the same cap on a power amp (60W), there was a loss in dynamic, but still it worked.

 

Edit: Forgot to mention it's a X2 cap, intended to operate safely even in the presence of spikes on the mains supply of up to 2.5 kV, using line voltages from 150 to 250 VAC (nominal) which are plugged into ordinary wall outlets. In Europe this covers a lot of ground: Computers, hair dryers, fax machines, hand power tools and so on. A cap that's RFI & EMI supressive, excellent self healing properties and of a metallized paper construction (highest possible safety regarding active and passive flammability) should suffice.

 

Don't know how much of this applies to US, but the logic should be somewhat the same.


Edited by Albedo - 10/31/10 at 2:35pm
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