My formerly quiet Crack isn't!

[Nathan]

Until today, my Crack has been quiet as can be at any normal volume position. Only at the very highest position did I barely hear any noise.

Imagine my surprise today when I got home and turned on my Crack- HUMMMMM coming from both channels, equal in loudness, even at a low volume setting. Hum went up the higher the volume control. Tried various sources into my Crack, all the same.

Then I disconnected the input interconnects- and my Crack was once again silent. I've not touched my interconnects otherwise- my sources go into my crack through a very good switch box.

It's as though, over night, my interconnects or something has become an antenna.  What gives? All comments appreciated.

By the way, the IC is a Rega Couple clone which means it's Klotz LaGrange cable

When I can I will try some other IC to determine whether I still get noise.

My Crack is not quite stock- Tung Sol 5998 and Mullard 12au7, teflon bypass audio caps, film bypass power supply cap, padded down volume control and Cardas input jacks. The only other thing I can think of noting is that after noting this him I switched around some power cords and note that the Crack is quieter with a shielded power cord vs non-shielded

Thanks everyone!

[fullheadofnothing]

If you unplug the input from your Crack and the noise goes away, then the problem is not the Crack. Either your source or your cable is either creating or picking up noise. Remove components one by one to figure it out. Start by ditching the switchbox and plugging a source in straight. If you still have noise, try a different source. It could also be a ground loop. Is everything that is connected to anything in the system plugged into the same outlet?

[Nathan]

I tried a different cable, still got noise but the noise varied depending how I held the cables. Interesting. No cable = no noise

Bypassed the switch box- still have hum with sources directly connected to the Crack.

It's as though my formerly quiet home is now RFI infested!

As far as all plugged in to the same outlet- all the sources and the Crack are plugged into the same outlet. Only my integrated amp is on its own circuit but since that's not even used when I listen to headphones, that should not be a consideration.

Could I have some form of loose ground lurking?

[fullheadofnothing]

If that integrated is connected in ANY way to your Crack setup, having it on another circuit COULD be the cause of your problem. Or it could be another piece of gear connected to the integrated. Every detail you reveal about your system makes it sound more and more sprawling. Simplify to test, then add in complexity until you re-encounter the hum.

You know that with nothing connected the Crack is fine. What about with cables plugged into the Crack but not to anything else? What about to a single source? Then add the single source to an input of your switch box, the Crack to the output, and no other ins and outs. And so on. If none of these things reveal the problem, it is most likely environmental. Try the experiments in another location, even if you can only do it temporarily. What are the sources? Do they share a common denominator (i.e. are they all DACs connected to the same computer?). We know it's a system problem, but you haven't explained what the system is.

Everything matters when evaluating these issues, including cables (type, construction (how are those solder joints looking?), routing, et cetera), power, other nearby electrical/electronic devices, and so on.

[Nathan]

For reasons unknown, things appear substantially quieter this morning. I only hear hum at volume settings far higher than I would use for actual listening.

Must have been an RFI attack. I'll call in the FBI, but I suspect North Korea as I was one of those that rented The Interview (glad I did not buy 4 movie tickets to take my family to the theatre to see that one)