[SoulSyde]

I'm not sure if this of any consequence to this discussion but I had a similar issue a couple of years ago with my Bifrost and Asgard and the culprit was a bad ground. I had an electrician at my house for some other work and I asked him to rewire the ground and replace the GFI outlet in my listening room. The end result was the disappearance of my "hum."

Ground loops can be a PITA. Good luck!

 

[tim79b]

  I mean to physically disconnect the USB cable from the DAC. We have to get the Mini out of a another possible loop. Changing the input on the front pannel will not do it. Just a bit more troubleshooting may pointpoint the issue.

Ahh - gotcha
 
OK - disconnected the USB from the DAC - still humming...
 
so the only thing that completely kills the hum is unplugging the inputs from the Lyr...
 
I've found a place about 20 min up the road from work that has a Furman AC210 in stock - will a power conditioner help?
 
Cheers

 

[SoulSyde]

Ahh - gotcha

OK - disconnected the USB from the DAC - still humming...

so the only thing that completely kills the hum is unplugging the inputs from the Lyr...

I've found a place about 20 min up the road from work that has a Furman AC210 in stock - will a power conditioner help?

Cheers

Have you tried setting it up in a different room on a different electrical circuit in the house? Your issue could be limited to that room of the house if in fact it is a ground issue with the outlet.

 

[tuna47]

Did you try different tubes in your lyr

 

[syvlvr]

In my case, yes some conditioning helps. I have a Lyr, which has a distinct hum/buzz that distracts from the sound. I tried a product from MCM Electronics, called a dual channel ground loop isolator. I no longer hear the hum. Amazon: http://www.amazon.com/MCM-50-9040-ISOLATOR-CHANNEL-UNBALANCED/dp/B008I5RQO2/ref=sr_1_1?ie=UTF8&qid=1384442801&sr=8-1&keywords=mcm+ground+loop
 
I also use one on my Musical Paradise Mp-301 integrated tube amp for the same reason. To me it seems like tubes are more sensitive to 60hz issues. But I'm no expert.

 

[joebobbilly]

 
Ahh - gotcha
 
OK - disconnected the USB from the DAC - still humming...
 
so the only thing that completely kills the hum is unplugging the inputs from the Lyr...
 
I've found a place about 20 min up the road from work that has a Furman AC210 in stock - will a power conditioner help?
 
Cheers

 
Have you tried different interconnects? If unplugging your monster cables removes the hum... perhaps try diff cables?

 

[ngyu]

 
Ahh - gotcha
 
OK - disconnected the USB from the DAC - still humming...
 
so the only thing that completely kills the hum is unplugging the inputs from the Lyr...
 
I've found a place about 20 min up the road from work that has a Furman AC210 in stock - will a power conditioner help?
 
Cheers

several things to try/consider:
 
are both the bifrost and lyr on the same outlet/power bar?
have you tried unplugging everything else (power-wise and signal wise) near the bifrost/lyr?
have you tried the stack elsewhere in the house?
 
better to try free solutions than paid ones first =)

 

[sceleratus]

   
Have you tried different interconnects? If unplugging your monster cables removes the hum... perhaps try diff cables?

That's a pretty good indicator of a ground loop.  See link F-G in the diagram a few pages back.  Unplugging the cable removes the "loop".  Interconnects "shouldn't' fix a ground loop because all interconnects are conductors, and conductors complete the loop / circuit.
 

  several things to try/consider:
 
are both the bifrost and lyr on the same outlet/power bar?
have you tried unplugging everything else (power-wise and signal wise) near the bifrost/lyr?
have you tried the stack elsewhere in the house?
 
better to try free solutions than paid ones first =)

Free is indeed better and fixing the root cause is best.  There may be another circuit in the house that doesn't have a second ground or stray voltage.
 
I remember reading a similar thread months ago where someone had other audio devices didn't have a problem, only the Bifrost on that circuit. 

 

[LibraryGuy]

On ground loop-style hum; my common culprits have been CCFL light bulbs and cheap dimmer switches.

 

[sceleratus]

  On ground loop-style hum; my common culprits have been CCFL light bulbs and cheap dimmer switches.

Now that's good to know !

 

[john57]

  On ground loop-style hum; my common culprits have been CCFL light bulbs and cheap dimmer switches.

I did had a severe problem with SCR dimmers in the past. In fact it damaged some of the power conditioning equipment I had at the time. It is more of a buzz sound not as much of a hum. CCFL light bulbs has more of a hum in my experience. What I did was to install a central single AC isolation transformer for all of my video and audio equipment. It was cheaper for me that using a AC double conversion power regenerator device. I am not using the SCR dimmer in the dinning room any more and not on the same circuit as my video and audio equipment.  

 

[sceleratus]

  I did had a severe problem with SCR dimmers in the past. In fact it damaged some of the power conditioning equipment I had at the time. It is more of a buzz sound not as much of a hum. CCFL light bulbs has more of a hum in my experience. What I did was to install a central single AC isolation transformer for all of my video and audio equipment. It was cheaper for me that using a AC double conversion power regenerator device. I am not using the SCR dimmer in the dinning room any more and not on the same circuit as my video and audio equipment.  

John,
What's the brand and model of your isolation trans?   I want to keep it in my back pocket.
 
Thx

 

[john57]

Did you try different tubes in your lyr

Tubes can be sensitive to noise especially the time I lay my cell phone next to the amp. It was a pulsing noise.   However that is not the issue that OP is having.
When the OP disconnected the inputs of the lyr the hum was totally gone. That tells me that the RCA cable is part of the ground loop. That happens when the AC grounds of the two equipment in question are at different potentials.  
By the process of elimination we found that the only way to reduce the hum was to move the power plug of the Bifrost to an outlet that is at a lesser potential to the AC ground of the Lyr. I am not sure if the OP did the best moving the power cord of the Bifrost as close to the same power outlet of the Lyr. I sometimes use a cheater plug or an extra power cord that had the grounding pin cut off in the past as a troubleshooting tool. I would put the cheater on the Bifrost and leave the grounding of the Lyr alone. In fact I have heard Schiit technical support was saying that in another post.  The OP should try one other pair of interconnects between the Bifrost and the Lyr. A cheap pair is fine and I always have an extra one on hand since I have quite a few equipment that uses the same type of cables but I have the feeling that it may not fix the issue. That depends if the monster cable has a shield ground connected to the signal ground on both ends.  Syvlvr mention a dual channel RCA cable ground loop isolator which may work in OP case since it works for Syvlvr. I would make sure that the house grounding scheme is good as it can be and you may need to hire an electrician to do this but may avoid problems in the future. Having your audio and video equipment on the same circuit is a good idea.

 

[sceleratus]

Please add....
Do Not Clip the Ground or use a cheater plug.  It's dangerous. The cheater plugs were used to facilitate using a NEMA 5-15Plug in older construction with non-polarized 1-15Receptiles (2 prong).  IMO, safety first, I don't think it should be used just for testing either.  The Lyr has several hundred volts under the case and you do not want to become a ground.  You don't know what might be touching the case.
 
This is an example of 450V of in a tube amp.   While testing my 300B the DMM probe skated...
The MOSFET's fractured in two.  Several resisters were eviscerated too.   
 

 

[john57]

That why I said the Lyr should always has its AC ground connected
For Schitt tube products I know this regarding plate voltage for tubes as per Jason at Schiit:
 
120V in the Valhalla on a 210V rail, 100V in the Lyr on a 200V rail.
 
I had a custom 6AS7 built amp that one of its tubes arc over and send HV to the headphone and blew it out. I use micro grapers on my DMM only a small tip is exposed. I had my share of skating probes. I have not used cheaper plugs in many years just on old 2 plug outlets no longer in the house.