Well this is frustrating ...

[Deke609]

I don't think the hum was originating in the BeePre (which I have since dismantled and bought a whole bunch of parts for rebuilding).

I've been jonesing for music, so today I hooked up the Nickel Wonder preamp which has litlerally been gathering dust in a corner since I put it together. Fed it to the Kaiju. Headphones on: instant hum. So I think "!@&$ ^$%!@ **&%^# It's the Kaiju! I must of $#%&ed something up when I installed the snubbers!" So onto the worktable it goes but I don't see any problems. So I put the SII-45 after the Nickel Wonder - same hum!

So then I'm thinking I've blown the drivers in my LCD4s and that kinda freaks me out. So I rig up a headphone amp fed by the Nickel Wonder and try different HP's - same hum.

Then I changed all the cables and power cords. Same hum. Took everything off the dedicated 20A line from the box and put everyting on a regualr 15A line. No change.

Tried unplugging just about everything in the house. No change.

So I thought maybe there's something wrong with the grounding in my house wiring. But my Emotiva dc-offset filter indicates that ground is a-ok. Is there a better way to test the house ground?

So its some other noise on the mains? But what are the odds of the mains going wonky at the exact time that I install snubbers in my BeePre and Kaiju?  The City was rewiring the mains over the summer (resulting in even lower mains voltage!), so maybe that's it.  But I'm pretty sure I had both amps working silently after they did much or all of that work. So I'm doubtful. But maybe.

But it just occurred to me as I type that I did change something in the amps: I removed PB's chassis ground elevator diode mod b/c I was worried it might be interfering with all my shielding wired to chassis ground. I'm going to reinstall them and see.

What's weird to me is that I only hear the hum when the power amp (Kaiju or SII-45) is connected to a preamp (BeePre or Nickel Wonder). Remove the IC's and the hum disappears. Does that point to anything in particular as being the culprit.

Man ... I can't believe I tore down what I'm thinking was likely a perfectly working BeePre 

Any and all suggestions for how I should troubleshoot this will be appreciated!

cheers, Derek

 

[Doc B]

If you have an oscilloscope that is the best way to sniff out hum issues. You can see the shape and frequency of the waveform and that helps a lot to determine the source.

 

[Deke609]

If you have an oscilloscope that is the best way to sniff out hum issues. You can see the shape and frequency of the waveform and that helps a lot to determine the source.

Thanks Doc. I do have a scope. I will take a look at the mains.

cheers and thanks, Derek

 

[Deke609]

Well, the reverse paralleled diode mod didn't help.  And just to be sure, I listened again with a solid state headphone amp and different headphones -- and yup, the same hum.

So on to scoping mains power.  This is so weird.

 

[Deke609]

Well, I tried one more thing in an effort to narrow down the source to either inside the house or outside. I cut the breakers to everything except the dedicated 20A line that's used only for audio - no change. Still hums. So I suspect it really is something on the mains.

 

[grufti]

You might want to try the inverse. Cut the breaker to your 20A circuit for the audio equipment and then connect a very basic audio setup to one of the other [regular] circuits in your house. Hum of no hum?

 

[Deke609]

Good idea. But no luck. Still get hum.

I'm now wondering whether someone might have inadvertently disconnected the house earth ground.  I live in an old duplex circa 1895. The guy in the lower unit was doing a bit of reno in the basement over the last couple of months. I wonder whether he saw an old wire connected to a pipe and cut or removed it. He's away until sometime next week - but I'll ask him when he gets back. Maybe I'll need to get an electrician to put in a new earth ground.

 

[Paul Joppa]

Earth ground is not important for noise (only for safety ...)

What is connected to the input of the preamps?

BTW, Doc B's suggestion of using a scope to look at the device outputs and even the power line is still worthwhile. Post screenshots to crowdsource the analysis ...

 

[Paul Birkeland]

What's weird to me is that I only hear the hum when the power amp (Kaiju or SII-45) is connected to a preamp (BeePre or Nickel Wonder). Remove the IC's and the hum disappears. Does that point to anything in particular as being the culprit.

On your nickel wonder, the output is one winding of the transformer, is that floating in your build or did you ground one end?

The symptoms you are reporting are consistent with a grounding issue, and when you make your system more and more complicated, you provide more points where these issues can originate.  Your instinct to get things down as simple as possible is a good one.  I would follow Doc B's directions to see if that leads you anywhere.

If you have just one interconnect plugged in, do you still get hum?  If you just touch the shell of one RCA cable to the shell of the jack (leaving the center pin doing nothing), does that activate the hum?

 

[Deke609]

Many thanks PJ and PB. I'm confident that I will *eventually* get to the bottom of this.

Earth ground is not important for noise (only for safety ...)

This is good information to know. I didn't see your message until late at night, after tracking down where the main panel in the basement makes an earth ground connection: on the city water service pipe that runs about 10 feet below grade under my front yard.It was loose and corroded. So I spent a couple hours cleaning all the parts, filing to get shiny metal, and re-attaching. So hopefully my house is now safer!

What is connected to the input of the preamps?

My DAC. But the hum happens even when there is nothing connected to the inputs of the preamp.

BTW, Doc B's suggestion of using a scope to look at the device outputs and even the power line is still worthwhile. Post screenshots to crowdsource the analysis ...

Yes, this will be this morning's project. I will post screenshots of everything later today. Everyone's expertise (or even wild guesses) as to the meaning of the results will be much appreciated.

On your nickel wonder, the output is one winding of the transformer, is that floating in your build or did you ground one end?

I will check that later today and report back.

If you have just one interconnect plugged in, do you still get hum?

Yes, I still get hum.

If you just touch the shell of one RCA cable to the shell of the jack (leaving the center pin doing nothing), does that activate the hum?

No. it only happens when the center pin is connected.


Different idea: I remembered this morning that in August I had a water leak upstairs. I didn't notice any effect on audio at the time. But seeing the corroded earth ground connection last night got me thinking this morning: corrosion takes time. Maybe one or both of the outlets near my audio or elsewhere on my main floor are corroded. I will safely investigate this after scoping.

cheers and many thanks, Derek

 

[Jamier]

Derek, do you have one of those test plugs with the three lights that analyzes the configuration of an AC receptacle? It will tell you if you have an open ground. It won’t tell you about the quality of the connection, but it will indicate if your grounded or not. I always thought earthing of circuit grounds made a difference with respect to noise too, especially signal input grounds.

Jamie

 

[Deke609]

Scope shots attached.

Mains looks fine. Interestingly, the scope says I'm getting 121V RMS, whereas my Fluke 117 says 117 (perhaps it's biased in favor of itself). So maybe I need a new battery (again!). And maybe this explains why my voltages on checkout are always slightly on the low side.

Hum is a jagged 60Hz wave. With preamp connected but not powered on: no hum and no hum waveform. With preamp on: jagged 60Hz waveform that varies in amplitude by the SII's attenuator setting.

Please let me know if the waveform isn't clear enough, or if you want something else.

All input/thoughts welcome and appreciated.

I still suspect that my upstairs water leak in Aug has something to do with this - the water went right through the floor into the ceiling (and presumably the walls, perhaps using mains wiring as its conduit).

I am going test whether the hum is still there if I plug the amps into the wiring from the main panel rather than the sub-panel.

@Jamie - I had one of those at one time, but it's either lost or buried in some box/bin somewhere (which is as good as lost - I'll find 5 years from now when looking for something else)

MTIA, Derek

 

[Deke609]

On your nickel wonder, the output is one winding of the transformer, is that floating in your build or did you ground one end?

Forgot to answer this: It looks like I grounded it.

cheers, Derek

 

[Jamier]

Derek,

    Is your house wired through galvanized conduit, completely? You mentioned having a dedicated 20 amp audio circuit. Is that something you added or was it present when you moved in? In those circuits that are wired through the conduit are there no ground wires ( is conduit the ground pathway)?

Jamie

 

[Deke609]

Is your house wired through galvanized conduit, completely? You mentioned having a dedicated 20 amp audio circuit. Is that something you added or was it present when you moved in? In those circuits that are wired through the conduit are there no ground wires ( is conduit the ground pathway)?

Hi Jamie - no metal conduit that i know of. I should have chosen a different word. I just meant that I suspect the wiring in the walls would make an easy means/route ("conduit") for water to follow gravity.

I had electricians add the 20A line a couple of years ago and watched them put it in. They snaked a new wire directly from the box to the wall outlet.

cheers, Derek

 

[Jamier]

Is that wire romex? If it is it’s not likely be a problem except on the stripped ends which you can check easily. Did you turn off the circuit breaker and pull the duplex out of the wall box?

Jamie

 

[Deke609]

I'm not worried about the wires so much as I am about the receptacles and receptacle boxes.

 

[Jamier]

If it is dedicated it only has 2 ends. The duplex in your listening room and the connection at the service panel( unless it is connected through one or more service points, which should also be in metal or possibly plastic boxes).

Jamie

 

[Jamier]

Derek, turn off the breaker, AND BE SURE it is off, and pull the duplex out and inspect it. It’s possible that the problem could be as simple as a ground wire that’s become detached from the duplex. Not all electricians are as careful as others. Make sure when using the Sideties on a duplex to make a “J” loop on the wire in a clockwise direction so the screw pulls the wire in toward the screw shaft and thus cannot come loose. MAKE SURE you check those wires with a meter before you handle them.

Jamie

 

[Paul Birkeland]

With preamp on: jagged 60Hz waveform that varies in amplitude by the SII's attenuator setting.

That's a new piece of information.  If the attenuator is all the way down, is the hum nearly inaudible?  Is everything plugged into the same outlet? 

When you figure out what's actually wrong, it's likely to be something incredibly simple. 

Something I've had happen that could cause this would be one of the two connetions on an RCA jack not being connected.  Or, for instance, if somehow you swapped ground and signal hot, that could make a weird problem like this.