Not exactly a "source related" subject, but it has to go somewhere, so I thought to put it in here.
As you know quite many things I discover by accident. That they are "discovered" as such will be because I dive into whatever it is, and try to see merits. This is such a case;
For some days now I have a noise in the room. What noise ? well, the noise of too high (rev) running fans from my audio PC. Such a fairly slowly resonating noise which feels like air bouncing into itself, that influencing the number of revolutions of the fans. Fairly low pitched.
All logical, because the cooling fins of my audio PC are stuffed with dust. So, time to clean it (which must happen each 6 months or so).
That is what I thought ...
At testing the new prototype XXHighEnd audio machine (
Re: CPU considerations besides that machine needing a connection to the mains, there's also a monitor involved. This is a flatscreen with with an outboard switching PSU where a normal mains cord comes out to stuff into the wall outlet.
Knowing that monitors can be a real pain in creating groundloops (just measure what happens to your Protective Earth (base) potential somehow I didn't trust this monitor. Anyway, it found its ways to the mains to a normal house ring, and the prototype audio machine went into there as well. The DAC is in a separate audio ring with different earth pin (these things are important).
Already yesterday I found the noise becoming unbearable, especially while I was working on the being completely silent of the prototype machine. But okay, cleaning jobs are always for "tomorrow" and so I let it be.
Not being at location, I just received a call. "Hey, you remember that I told you yesterday that something is humming ?" yea yea, I told you, that PC needs cleaning. "No, it is your amps !".
Next a great gig happened, because someone out there thought to lay the phone on one of the amps and that really works like a nice microphone. Ouch, that sounded dangerous ! A firm rattle of 50Hz (we have 50Hz mains overhere). Next I was told that the whole amp was vibrating.
The amp of the other channel - same thing. Not as loud, but the very same thing. It can go away for a few seconds and come back. That resonating noise I tried to describe.
Well,
this and
that, I don't know yet. All I know is that I immediately had that monitor in my mind, and after trying out a few other things on purpose at first, indeed when the monitor cord was pulled out of the outlet, things went quiet again.
While this post merely is a first attempt to let you improve your systems, it has a reason that I tried a few other things first (like said in the before paragraph). Why ? well, because at putting back in the monitor cable, the sound did NOT come back. This is how ground loops work.
I don't know whether this is something new, but of course it is known that transformers can hum/rattle (on the mains frequency). So, that it is groundloop impeded could be a new thing, or in other words : that you can get rid of it without a new amp (design) could be new.
The thing is so hefty for its vibrating that it looks completely dangerous. But, the one amp was less severe on it than the other. What about yours ? or what about my own when things look all right while it still is not (like it being inaudible, not being able to feel it, but still happening at a lower level ?).
Here is your warning (and NEVER forget it !) :Already in the first 10 seconds the sound had more snap to it, and somehow B.B. King was so much present in the room. Hard to describe. But further down the line the real change became clear : slam, slam and more slam. I even went as far as stating "now *this* is a nice dance track", while I don't like dance at all and whatever it was is categorized under Lounge here. Completely crazy.
Oh, is that so Peter ? well done then.
But you must be on the wrong track with it, right ?
You should at least have connected that prototype machine the very same way as your normal audio PC. Use the same keyboard, the same mouse and especially the same monitor. All those may s*ck to begin with and may need explicit investigation so that part is for the better and not for the worse. But the least you should recognize, Peter, is that you are comparing apples to oranges now.
Oh sh*t. Where does this end ?
PS: None of this is audible through the speakers as rattle or hum.
