So I had this ridiculous noise problem (in hindsight it is now ridiculous, but during it was incredibly annoying). We've all had them and when we get rid of them they are always gratifying moments. And dumb-ass moments for not knowing to try that first! We tried just about everything we could think of in the component area and it turned out to be something silly. I reached out to Dave Elledge to coach me through running down the culprit and you can see by the string of exchanges we had that we tried some pretty silly things in the process of trying to eliminate components or typical fault areas. I had a HUMMMM that was less than a faulty cable HUMMMM and way more than the typical hssss we live with when the system is idling. When you can hear the HUMMM from your listening chair you have to try and eliminate it.
The result is it is resolved but look at the path we weaved over 2 weeks+ to get there:
Me:
Trying to resolve a noise problem with the system in new digs. I ran a 20 amp line and have the stop/uber powering the amps. I have a Furman IT-REFERENCE 7i into the same outlet with the preamp, dac, and a Emotiva DC blocker taking the HAL MS2 and hard drive.
I also have a 1.5kv EAC tranny available.
A little more hum through the speakers than I care for since I can hear it while seated. I am guessing I shouild try everything through the Uber next and skip the Furman. And then maybe try the Furman through the Uber?
I am guessing either the dac or the MS2 is the culprit. Is that good logic to try or?
Dave:
Yep, something in the lineup has a funky ground. I would try plugging the Furman into the Uber since balanced power units work off of a virtual ground... If that doesn't work, hit me with an email
Hang in there, Brother.
<><
A few days later:
Slow going on the noise problem. I tried everything through the Uber w/o any Furman device and still the same. Tried changing the input selector on the pre and it is constant for all settings. Tried turning off the dac and still there. Tried a cheater plug on one monoblock and still there. So my guess is the preamp. When I get time I will try checking the tubes and the interconnects. If no luck there I might pull the power cables up and away from everything to see if they are picking up noise. Unfortunately I have flouescent lights but even with them off therre is the same level of noise.
BTW, the noise is present only with the volume turned up and not when the volume is fully down. This says preamp to me. And I know that my preamp has no chassis ground.
I wonder if moving the breaker one notch down and picking up the other leg would work?
Dave:
Yep, it's the pre. Can you invert the plug from the pre into the receptacle? Silly I know, but it works on guitar amps.
Could be a heater in one of the tubes, too.
Both channels, Pete?
<><
Dave
More days passed:
Dave, I tried flipping the AC plug polarity, flipped the hard drive off, tried attaching a ground wire between the outer of an RCA jack on the pre to ground, and then put the pre on the Furman all by itself. I would say only a minute reduction in hum with the Furman. I should have measured it with the meter before and after.
I'll pop the top tomorrow and reseat the tubes and poke things around in there to see if that helps. If that doesn't work I'll pull the power cables up and out from behind the wire mess and see if they are causing the hum.
Pete
Dave’s response as we try to narrow down the culprit:
Yeah, Pete. I HATE hums. Try cleaning the tube pins and sockets with isopropyl alcohol or DeOxit. Sheesh... Did I say I hate hums?
Do you have any attachment to cable or satellite? Sometimes those things are the culprit. None of the installation techs care about anything than meeting code when it comes to grounds.
<><
Dave
Sent from my iPad
Then I had an AHA moment and finally stumbled upon the problem. When you are having no luck on your path it most likely is something totally unrelated and in left field. Here’s Dave’s final response to me finding the problem:
Like Gilda Radner said: "It's always something!" Sometimes it is that easily overlooked small thing like an unterminated cable.
Cool that everything is clean and tidy now. Good job, my friend!
<>
Dave
Sent from my iPad
On Oct 5, 2013, at 7:54 AM, "Pete wrote:
Found the problem! Pretty stupid but an easy fix. I had a "spare" ethernet cable running from the powered hub that was not connected to anything. I found this by unplugging the hub and the noise went away. Tried (it in) another circuit and it was still there. hmmmm So I noticed my spare red cat 5 laying next to my server and thought that could be it and when I unplugged it from the hub, whalla, fixed. Now I can stick with just the stop and the uber.
Of course I cleaned the pre tubes and tried reversing polarity on the amps as well. I was tipped off when I had the pre off and the amp on and the noise was still there. Kinda made the pre innocent at that point.
Awesome!
Pete
Dang Cat 5 was a transmitting antenna all the while and I was too lazy to notice it and just unplug it. Lesson learned is that if your system is capable of being quiet and all of a sudden it is not then you have probably introduced something new that is causing the problem. Hope this helps you someday if you have a noise problem.
