Dishwasher Interference

[Lavcat]

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?

[aardvarkash10]

do the dishes by hand...

[c2cthomas]

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.

[abraxalito]

Originally Posted by Lavcat

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.

[tauro0221]

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.

[Lavcat]

Originally Posted by abraxalito

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.

[Lavcat]

Originally Posted by c2cthomas

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.

[Lavcat]

Originally Posted by tauro0221

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.

[Lavcat]

Originally Posted by aardvarkash10

do the dishes by hand...

...Or I could put the records in the dishwasher.

[abraxalito]

Originally Posted by Lavcat

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).