Amp Transformer Hum

[Rubytuesday007]

Hi all,

I’ve run into an odd mains issue with my Burmester 956 Mk2. The amp develops a loud mechanical transformer hum whenever my dishwasher is running. Once the dishwasher is off, the amp is completely silent.

Setup details:

• Dishwasher is on its own circuit (upstairs).
• Listening room is on a 15A line on the opposite side of the breaker panel.
• Noise is strictly mechanical from the transformer, not audible through speakers

This makes me think the dishwasher is introducing DC on the mains / asymmetrical load, which is saturating the toroidal in the amp.

Questions:

1. Is this best addressed at the panel (balancing loads, neutral/ground checks, etc.)? Is it possible I have a wiring/load issue at the panel?
2. Would an inline DC blocker at the amp be an effective fix?
3. Has anyone measured or logged mains DC in similar cases to confirm?

Curious what others here have seen in practice. Thanks!

 

[Zek]

This makes me think the dishwasher is introducing DC on the mains

This is most likely the cause.
The dishwasher and the amplifier are probably on the same power phase (although not on the same fuse).
Try plugging the amplifier into a different outlet that is not on the same phase as the dishwasher.

Would an inline DC blocker at the amp be an effective fix?

You have to try that.
Sometimes it helps, sometimes it doesn't...

 

[sam_adams]

Would an inline DC blocker at the amp be an effective fix?

The Emotiva CMX-2 has proven effective by many in this type of situation. A member here tested the CMX-2 with some of his own equipment and came away with varying results. You will have to judge for yourself if this would be an effective 'fix' in your circumstance.

 

[DVDdoug]

I have an amp that had that problem when my old TV was turned-on. Since the TV has been replaced the problem is gone. At the time I didn't know about DC offset. The amp is still fine. In my case it was plugged into the same outlet as the TV. (My amp has a normal laminated transformer.)

Since that seems to be an expensive amplifier you might want to try changing the dishwasher. Or get a different (perhaps more economical) amplifier. (Personally, I wouldn't pay more than about $1 per watt.)

Or maybe don't wash dishes when the amp is on...

 

[Rubytuesday007]

Thanks for the replies. Obviously the easy solution is to not run the dishwasher. However, I’m wondering if there’s something I could do at the panel level to fix this? Would a dedicated 20amp circuit help? If yes, is there instructions I can tell the electrician?

 

[Zek]

Here in Europe, households usually have three-phase electricity.
Try to separate the phases where the dishwasher and amplifier are connected if possible.

 

[solderdude]

However, I’m wondering if there’s something I could do at the panel level to fix this? Would a dedicated 20amp circuit help? If yes, is there instructions I can tell the electrician?

probably not unless you have the rooms on a different phase in which case an electrician could select different phases for the stereo and dishwasher.
When there is only 1 phase then It would depend on the total wire resistance between your house and the distribution point where that cable ends.

 

[egellings]

I have an amp that had that problem when my old TV was turned-on. Since the TV has been replaced the problem is gone. At the time I didn't know about DC offset. The amp is still fine. In my case it was plugged into the same outlet as the TV. (My amp has a normal laminated transformer.)

Since that seems to be an expensive amplifier you might want to try changing the dishwasher. Or get a different (perhaps more economical) amplifier. (Personally, I wouldn't pay more than about $1 per watt.)

Or maybe don't wash dishes when the amp is on...

Maybe put the amp and washer on different electrical circuits.