[doctorcilantro]

I have a dedicated 20A circuit with Cullen modded AC outlet feeding an Emotiva CMX-2 DC blocker feeding a PS Audio P3 (which also blocks some DC current) and I can still hear a buzz when my dishwasher is on. I can hear the P3 tranny buzz pretty loud at times especially when dishwasher is on.

I also have a small bit of hum but might be amp design tradeoff because it is a low-level and quiet, especially compared to some other SS amps I have tried here.

Maybe Neutral is contaminated? I don't think a cheater plug on the amp fixes the buzz.

Things I have tried:

test Multiwave and Cleanwave NO CHANGE
Try both into CMX-2 NO CHANGE
turn off every breaker except audio (not yet)
Connect amp and DAC to same Cullen outlet NO CHANGE
try cheater plug on amp NO CHANGE
Try another DAC: NuWave UDAC NO CHANGE
unplug USB from DAC NO CHANGE
shorting plugs LOW LEVEL HUM
source cables unplugged from amp LOUD BUZZ AND HUM
Star grounding not yet
when connecting ground wire from DAC to amp floated tranny NO CHANGE
Test DAC with SS amp and XLR cables SS AMP PSU HASH LOUDER THAN TUBE AMP HUM

[Big Red Machine]

Have you considered a heavy duty extension cord to a completely different circuit for the whole system, both with the existing stereo circuit breaker on and off?

[doctorcilantro]

Good idea I will try that.

[doctorcilantro]

Have you considered a heavy duty extension cord to a completely different circuit for the whole system, both with the existing stereo circuit breaker on and off?

Well, 1 problem possibly solved. Thanks BRM!

The Office line is in the same power leg as dishwasher but the buzz doesn't appear when using that circuit for Audio.

The P3 is powered down, and moved it between Office and Audio circuits results in:

Dishwasher in mid-cycle

• LOUD buzz with P3 off - Audio circuit (can easily be heard from listening position)
  
• No audible buzz (unless ear on P3) - Office Circuit

My guess is that it's too much Direct Current for the P3 to fully block.

[doctorcilantro]

The trouble is that I don't know what to do about it.

My dishwasher is provided by my employer. I can try to show them the loudly buzzing device in another room, but I might get cross-eyed looks. I will call the dishwasher crew though, but will a replacement fix the issue?

Or, should I just try to switch the wiring at the breaker panel? Could it be a bad breaker? why doesn't the noise creep through the Office circuit when it's on same leg as dishwasher. Should I swap the two at the breaker?

[Big Red Machine]

Clean sound on the office circuit?

Noisy sound on the stereo circuit?

If so, then the stereo circuit has a problem?

[doctorcilantro]

I'm tempted to swap the wiring at the circuit board, but first there is a lightswitch I think Audio circuit runs through. Maybe the ground connection is bad there or at another outlet.

[Speedskater]

If you live in the US/CAN get a little "Kill-a-Watt" meter and measure several outlets. Measure both when the dishwasher is running and when it's off.  Does the voltage change whin you run the dishwasher (voltage up or down)?

[roscoeiii]

My guess is that it's too much Direct Current for the P3 to fully block.

That crossed my mind too. You might benefit from a more burly DC blocker, maybe the one that Frank Van Alstine is offering? It has a resonable price and I think I recall comments on it working better than some other DC blockers. 30 day return policy...

[avahifi]

We do know that our HumDinger did work in some cases where the Emovita did not, although it does not have all the features of the Emovita.  Its just a plain Jane box for $125 with a 30 day satisfaction guarantee.

Frank VA

[doctorcilantro]

I thought the voltage was reading higher than normal with dishwasher on, 121V.

I was reading the input voltage on the P3. But now it seems it is still up there at 121v with it off. Usually its at 115-118.

 It is raining outside which is rare here.

Should I open up the other outlets on the circuit and check the ground?

If the other circuit is ok, with no buzz, maybe it's the wiring at the outlets in Audio circuit...

[doctorcilantro]

It's night here, and raining.

No major appliances on anywhere in house.

Office circuit reads 119V on P3 when I turn off NAS and i7 computer.

Audio circuit reads 121V on P3 with nothing on in room, AND the P3 buzzes very loudly!

confusing...

I would love to test the P3 on a cheater plug, if safe to do so momentarily.

Do breakers go bad? I'll have to re-check the wiring there as well, but again, the outlets and the switch which controls one of them - seems like room for error there.

[avahifi]

In your first post, you said when you disconnected the source cables from the power amp, did you disconnect them at the power amp end or the preamp end?  If you disconnected them at the preamp end I would expect the hum you reported.
 
If you disconnected the source cables at the power amp end, so only the power amp was connected to the speakers, I would not expect hum from the speakers unless the power amp is defective.

If the amp is connected to the speakers only, with no other connections, there cannot be any ground loop hum connections, unless you are using active powered speakers that each also have AC power connections.

Which is the case here?

Frank Van Alstine

[jea48]

We opened the panel, electrician and I, and I took pictures.

When I measured the wiring coming out of wall for dishwasher it found what seemed to be 2 hot wires and a ground. One of these hot wires goes to chassis. Dishwasher says 120V (of course I can find no info online about the model!):

• 

Today, I put a cheater plug on the amp for testing only, hooked it up to an AC regenerator, and turned on the dishwasher.

A loud buzz comes out of the speakers when dishwasher is running.

At this time, I measured 20V AC across chassis of DAC to + Rachel binding post, 30V AC across AC Regenerator chassis to + Rachel binding post, and 3v from chassis of Rachel to + Rachel binding post. Trying to measure DC just kept rising.

Also , the noise filter just mentioned appears to only filter noise above 80kHz, and this buzz is very audible.

• 
• 
• 
• 

doctorcilantro,

An interesting thread. I have been following it for a while. Your above pictures peaked my interest today. Could you take a picture of the top part of the panel? One of the pictures showing the bottom of the panel shows a close up of the feeder, left hand side, that is the feed for the panel. I see 4 insulated conductors exiting the feeder conduit. Is the panel 3 phase 4 wire? 3 hot conductors and a neutral  conductor?

What Kind of building structure do you live in?
Jim

[jea48]

I pulled out the dishwasher, and the conduit wiring comes in wrapped in white sheath. It has (3) wires: green, black, and yellow.

These are wired: black/brown (HOT) | white/blue (7-9v) | yellow/chassis (7-9v)

There is also an internal green ground wire coming down out of dishwasher harness that goes to chassis.

I have the breaker off, and curious why the yellow goes to chassis. Doesn't seem right based on what I'm reading but who knows how it is really wired at breaker.

Proceeding with caution.

It has (3) wires: green, black, and yellow.

 The yellow wire could be a discolored white wire.


These are wired: black/brown (HOT)   .. OK.

white/blue  | yellow/chassis   .. Not OK.

The white/blue  | yellow/  wires should not be bonded, connected, to the chassis of the appliance. In the USA that is a NEC code violation.  The Neutral and equipment grounding conductor shall  be connected together at the main service equipment and at NO point thereafter.

There is also an internal green ground wire coming down out of dishwasher harness that goes to chassis.
That is where the green color wire, (the equipment grounding conductor), of the branch circuit feed should be connected to.

With the neutral conductor and the equipment grounding wire connected together by the common chassis connection the equipment grounding conductor will carry neutral load current back to the  electrical panel whenever the dishwasher is being used.
The branch circuit neutral conductor should only be connected to the white/blue of the dishwasher. Break the connection to the chassis.

Another neutral current path I see is if the dishwasher water feed is connected by copper tubing to a metallic water system. I see all kinds of neutral current ground paths.

And if the hot water line to the dishwasher is not metallic.....
 If for any reason the branch circuit neutral conductor and equipment grounding conductor connection were broken back to the electrical panel and the dishwasher was turned on the chassis of the appliance would be HOT.
Hot branch circuit conductor connected to  black/brown lead of appliance >> through appliance connected load >> out white/blue appliance lead >> to connection to chassis. HOT 120V chassis with reference to ground.
Jim

[doctorcilantro]

In your first post, you said when you disconnected the source cables from the power amp, did you disconnect them at the power amp end or the preamp end?  If you disconnected them at the preamp end I would expect the hum you reported.
 
If you disconnected the source cables at the power amp end, so only the power amp was connected to the speakers, I would not expect hum from the speakers unless the power amp is defective.

If the amp is connected to the speakers only, with no other connections, there cannot be any ground loop hum connections, unless you are using active powered speakers that each also have AC power connections.

Which is the case here?

Frank Van Alstine

I have tried 2 DACs.

DAC>Power AMP (no attenuator)>Speakers (passive 98dw/w)

AMP with shorting plugs = hum (if room is 32dba, at 1ft the hum is 40dba)
AMP with no input cables connected = buzzing and loud hum (it's a point to point Decware tube amp - see pics - maybe this is expected)

That said, the amp is overall very quiet as I do not hear any of the hiss I did when I connected up a Bel Canto SS. I could easily here the noise floor of that amp, and while at a similar amplitude, the hiss and hash seemed much more "intrusive" than the low-level hum of the tube amp. Still, I'd like to be rid of it if possible.

I will record the sounds tonight.

[doctorcilantro]

doctorcilantro,

An interesting thread. I have been following it for a while. Your above pictures peaked my interest today. Could you take a picture of the top part of the panel? One of the pictures showing the bottom of the panel shows a close up of the feeder, left hand side, that is the feed for the panel. I see 4 insulated conductors exiting the feeder conduit. Is the panel 3 phase 4 wire? 3 hot conductors and a neutral  conductor?

What Kind of building structure do you live in?
Jim

Hi, thanks for your interest. I live in a semi-connected, not sure of the right terminology, structure with two dwellings on either side. It's almost a standalone house, but shares maybe one wall. I live overseas where the country is 220v but we (13-20K people) are provided 110v.

I will get the panel off because #27 is my audio circuit, and if you can see in the pictures it is adjacent to a larger breaker and looks like an extra cable there, but the angle is bad so I'm not really sure. It would be interesting to simply swap the wiring at breaker to the Office breaker if it will reach. I will get the pics uploaded asap. FWIW, I remember one large wire coming in and then looked like two legs branching out to each side of breaker panel.

thanks, and here is a better quality image:

• 

[doctorcilantro]

It has (3) wires: green, black, and yellow.

 The yellow wire could be a discolored white wire.


These are wired: black/brown (HOT)   .. OK.

white/blue  | yellow/chassis   .. Not OK.

The white/blue  | yellow/  wires should not be bonded, connected, to the chassis of the appliance. In the USA that is a NEC code violation.  The Neutral and equipment grounding conductor shall  be connected together at the main service equipment and at NO point thereafter.

There is also an internal green ground wire coming down out of dishwasher harness that goes to chassis.
That is where the green color wire, (the equipment grounding conductor), of the branch circuit feed should be connected to.

With the neutral conductor and the equipment grounding wire connected together by the common chassis connection the equipment grounding conductor will carry neutral load current back to the  electrical panel whenever the dishwasher is being used.
The branch circuit neutral conductor should only be connected to the white/blue of the dishwasher. Break the connection to the chassis.

Another neutral current path I see is if the dishwasher water feed is connected by copper tubing to a metallic water system. I see all kinds of neutral current ground paths.

And if the hot water line to the dishwasher is not metallic.....
 If for any reason the branch circuit neutral conductor and equipment grounding conductor connection were broken back to the electrical panel and the dishwasher was turned on the chassis of the appliance would be HOT.
Hot branch circuit conductor connected to  black/brown lead of appliance >> through appliance connected load >> out white/blue appliance lead >> to connection to chassis. HOT 120V chassis with reference to ground.
Jim

I think even though it is a USA model, that they might have used European color coding which is different. IIRC, the wiring made sense. I also checked the chassis with a multimeter and it seemed ok. I will double check. Thanks for your indepth post.

Furthermore, I'm 99% convinced it is the Audio circuit after last night with nothing connected and the P3 buzzing away, but when swapped to the Office circuit...nothing. Would you agree this seems to point to the Audio circuit?

[doctorcilantro]

I pulled out the dishwasher, and the conduit wiring comes in wrapped in white sheath. It has (3) wires: green, black, and yellow.

These are wired: black/brown (HOT) | white/blue (7-9v) | yellow/chassis (7-9v)

There is also an internal green ground wire coming down out of dishwasher harness that goes to chassis.

I have the breaker off, and curious why the yellow goes to chassis. Doesn't seem right based on what I'm reading but who knows how it is really wired at breaker.

Proceeding with caution.

The colors listed above do not make sense, and I thought I had made a correction at some point. I will have to pull it out again and take pics.

The Office and Audio circuits are on breakers A and B respectively. A being the first ROW, and B being the second row, etc.

Does this mean they are on different legs? If so, maybe getting the Audio circuit onto leg B would help.

Or if easier, I will have the Dishwasher moved onto leg A.

[One and a half]

If you touch two components and the buzz changes, the equipment is being used as an earth return which is not right.

The photo of the receptacle with the wire nut on the earth line, looks too small to me, should at least be the same as the other conductors. I would go through every receptacle and check the connections, especially the earth wires.