Dishwasher Interference

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Night before last I happened to be running the dishwasher while listening to a record. Not something I usually do. What I noticed is that each time the dishwasher changed cycles there was a pop in the music.

The pops may have been a result of a spark at each change of cycle, but I am unsure of the route the interference got into the system. Furthermore if the dishwasher can make a big pop, other things are probably causing less drastic interference.

Anyone have any thoughts? Would an isolation transformer help?
 
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How old is the wiring in your house? It is common in older houses that the electrical circuits are widely shared and if your dishwasher and system are on the same circuit this could be a problem.
Do your electrical outlets have grounds on them? Ungrounded electrical outlets are much more prone to picking up interference than grounded ones.
How old is you dishwasher? If is an older model it might be using relays or a cycle switch with electrical contacts that are arcing when the machine changes cycles.

An isolation transformer should help if the dishwasher and audio system are on the same circuit. If the interference is being caused by arcs in relays or switches - hmmmm - that's gonna be a problem - perhaps solved by new switches - or relays - or new dishwasher.

A power line conditioner could help - but they can get expensive depending on how much power your system needs.
 
Anyone have any thoughts? Would an isolation transformer help?

Dedicated mains spur for your audio system, together with broad-band mains filtering with built in surge suppression. If that fails, snubbers fitted across the arcing contacts of your machine. Isolation transformer might help but probably only if the dishwasher is dumping noise on the earth wire.

Something like this though probably contains more than just the trafo -

2.5 KVA Noise Cut Transformer (901 series)

Since its not being marketed as a 'high end' audio solution, you'll probably get good value for money here :) I have no connection with these people btw but technically they look very much on the ball so to speak.
 
Hi,
Install a 130 to 150 volts metal oxide varistors in the outlet. It will protect the equipment against over voltage transients such as lightning, power contact, and power induction spike coming from the turn on of the dish washing machine. Mouser part number 652-MOV-07D151K. Normally what I do is install 3 mov in the outlet in a delta. One ground to live wire, live wire to earth ground and ground to earth ground. One thing that you would have to have in mind is that in case of a lightning it will trip the breaker.
 
Dedicated mains spur for your audio system, together with broad-band mains filtering with built in surge suppression. If that fails, snubbers fitted across the arcing contacts of your machine. Isolation transformer might help but probably only if the dishwasher is dumping noise on the earth wire.

Something like this though probably contains more than just the trafo -

2.5 KVA Noise Cut Transformer (901 series)

Since its not being marketed as a 'high end' audio solution, you'll probably get good value for money here :) I have no connection with these people btw but technically they look very much on the ball so to speak.

It looks just like an isolation transformer from the schematic, and one drawback is that it is for 220v. Plus, any time I see "Request price and delivey information," I think "expensive". I had in mind more of a 500VA unit.
 
How old is the wiring in your house? It is common in older houses that the electrical circuits are widely shared and if your dishwasher and system are on the same circuit this could be a problem.
Do your electrical outlets have grounds on them? Ungrounded electrical outlets are much more prone to picking up interference than grounded ones.
How old is you dishwasher? If is an older model it might be using relays or a cycle switch with electrical contacts that are arcing when the machine changes cycles.

An isolation transformer should help if the dishwasher and audio system are on the same circuit. If the interference is being caused by arcs in relays or switches - hmmmm - that's gonna be a problem - perhaps solved by new switches - or relays - or new dishwasher.

A power line conditioner could help - but they can get expensive depending on how much power your system needs.

This is an apartment, not a house, and I can't do anything about the wiring. I assume the dishwasher does have electrical contacts that are arcing. Just like everyone else's dishwasher in the building.


Edit: Yes, the outlets have safety grounds.
 
Hi,
Install a 130 to 150 volts metal oxide varistors in the outlet. It will protect the equipment against over voltage transients such as lightning, power contact, and power induction spike coming from the turn on of the dish washing machine. Mouser part number 652-MOV-07D151K. Normally what I do is install 3 mov in the outlet in a delta. One ground to live wire, live wire to earth ground and ground to earth ground. One thing that you would have to have in mind is that in case of a lightning it will trip the breaker.

Again, this is an apartment not a house, so I don't think MOV's in the outlet are an option. Also I've read that MOV's are noisy and should not be used in an audio appication? I have no experience, one way or the other.
 
It looks just like an isolation transformer from the schematic

Yes, I looked at that schematic and thought to myself 'Ah, they don't want to give away proprietary stuff there'. Just looking at the noise suppression specs I'd say its more than just a transformer.

.. and one drawback is that it is for 220v. Plus, any time I see "Request price and delivey information," I think "expensive". I had in mind more of a 500VA unit.

Yes weird given that they're a US based company I agree. Expensive in audiophile terms is a different matter to expensive in industrial terms. I have a couple of toroidals (500VA as it happens) which I bought for isolation purposes. They do isolate very nicely (ground leakage currents are down 20dB or so) but they still let through the hash. I had them custom made, the price was around $50 each I think (in Chinese money).
 
If you want a plug in solution, I recommend Sola constant voltage transformers. They are good against lightning,also.
If the device is not in a ferrous steel box, RF may still cause interference. I killed a noise from the flourescent light in my mixer by installing chokes on the hot and neutral AC lines coming in the steel box. I made the chokes out of toroid transformers from switching power supplies, leaving 25 turns of a single coil on each one. The chokes are installed inside the mixer.
I also installed an MOV but this is for a different problem. We have a lot of lightning here.
 
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and the correct answer is...

do the dishes by hand...
:D
else consider recycling paper plates...

one thing that I seem to always not do is being particularly careful of routing phono interconnects and ensuring proper grounds. Having never tried this next item, I am relying on other's experiences: Cardas RCA grounding caps on all unused inputs. I'm going to make some DIY ones and see what happens.

I use a "Pure A/V" (Belkin) MOV equipped filtered surge protector on my gear. I haven't noticed any issues with electrical "pops" since installing. I think I bought it for $40 or so at Costco some time ago. If they get more at my local Costco, I'll buy a few more. It's always good to have a spare or two around even if they only get used with the computer.
 
if the noise is only while playing records it is most likely RF into the phono preamp input. Check the ground and shields connecting it to the cartridge.

Yes, this interference is while playing records, not on other sources.

Tonight I checked the ground wire to the phono preamp and it was intact. Somewhere underneath the turntable there could be a bad connection I suppose.

My phono preamp (which is a cheap one) brings in WHRI Home on 3.215 MHz in addition to the dishwasher. If I turn all the gains way up I can get reasonably good signal quality. It would be nice if it came with an adjustment for selecting stations though.
 
The one thing Herald Electronics did right on the disco mixer is put disk capacitors on the phono inputs to ring ground. I forget the value, but try some- it shouldn't take much capacitance to get rid of 3 MHz and not hurt 20 khz. I've got a bunch of 22 pf disks I use from a RS grab bag of the 1970's, but I think that program has been replaced by e-bay or something. Half the grab bag parts were junk, sounds like E-bay doesn't it? Don't use wound plastic film or paper capacitors, too much inductance.
I used to have a 1961 AD? cartridge that would pick up the Navy sub-sonic communication program. Beep-Boop-Doop- over and over - repeated always three times. That was really annoying. The Grado FTE cartridge got rid of that for some reason without any other change. I'm using Shure N97HE era IV cartridge now, no beeps or crackles with either the disco mixer, or the PAS2 tube preamp.
 
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Lavcat, you've already answered your own question.

Yes, this interference is while playing records, not on other sources.

Tonight I checked the ground wire to the phono preamp and it was intact. Somewhere underneath the turntable there could be a bad connection I suppose.

My phono preamp (which is a cheap one) brings in WHRI Home on 3.215 MHz in addition to the dishwasher. If I turn all the gains way up I can get reasonably good signal quality. It would be nice if it came with an adjustment for selecting stations though.

So I would consider a couple of things.
  • If your current amp or receiver can be replaced (not necessarily costing a lot of money ), consider a vintage one. The included phono stages in those were not great , but quite acceptable. I purchased what I think is a great sounding receiver (Nakamichi SR2). The tuner portion is a little on the weak side, but the rest of it is quite good. I think I paid $35 for it. Haven't checked on recent prices.
  • Look at some of the inexpensive (but good) phono stage kits out there.
  • consider taking your phono stage apart and replace almost alll components in it
  • If your phono stage is a "newer" one that performs poorly, keep the enclosure, and gut it. Then do the DIY kit.
  • Check the phono leads you are using. Cheap (free-bee types or something you can buy for $1 or two), get some (make or purchase) better cables.

    As I didn't see a list of equipment, I can't comment specifically, but I suspect the wiring and the phono stage , as well as the AC coming from the wall.




 
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