Hissing, crackling, popping, only getting worse.

[NotaLefty]

Hi. My friend just built a Crack and then sold it to me. He said it worked perfectly for him. When I was using it, it sounded great for the first day. After that, the right channel made a slight hissing noise that grew worse until it sounded like it was destroying the right driver. I tore the headphones from the jack and asked my friend (who built it) to come take a look at it. He came over, brought his headphones, and it seemed to work fine for the hour or so he tested it. I tried a new pair of headphones, thinking it may have just been my headphones. Nope. The hissing on the right driver came back, although it didn't get as bad as it did with my other headphones causing me to stop listening. This hissing was an intermittent but audible hiss and crackle in the right channel. I give the Crack back to my friend for a few days and he says he went over some of the solder joints. I just got it back tonight, and I plugged my headphones in and was startled to hear that there was a much louder hissing, crackling, and popping sound coming from both channels. I never got a chance to try playing music from it because the sound made me fear for the life of my HD800. What is going on? Could anyone please help?

[Doc B.]

The place to start might be trying different tubes. They can hiss and crackle.

[NotaLefty]

We just redid a few of the solders. It is now working, but there is still buzzing when it is plugged into a source. We have tried multiple RCA cables and there is a distinct buzzing in both channels, whether or not the DAC is on or off, as long as the RCA cables are plugged into it. The volume knob on the Crack will also change how loud the buzzing is. Possibly a separate issue - when plugged in with my phone as the source, there is a different, quieter buzzing that goes away once music is playing.

EDIT: When the RCA cables are plugged into the Crack but NOT the DAC, there is no buzzing.

[Grainger49]

You have found that the buzz is caused outside the Crack.  Just be certain that the ground solder joints on the RCA jacks are good.

If you have a noise prone source like a cell phone or a computer near your Crack it can cause all sorts of problems.  Keep them 3' away while troubleshooting.  Then bring them nearer to find if they are the source of the noise. 

[Doc B.]

You might try the forum search function. There are quite a few threads dealing with how users solved an issue of gear ahead of the Crack creating noise, some as recent as a couple of days ago. They may give you some ideas to try. Connecting chassis grounds together (Crack and source component) with a wire jumper often helps.

[NotaLefty]

Okay, now I'm really confused. I just listened to the Crack with the exact same setup as before, and now it works fine. Nothing has changed. Yes, it is working now, but what was wrong and how can I prevent it happening again?

[Doc B.]

We don't really have enough information. Possibly the issue was from an outside source like a cell phone or an appliance. Possibly you reconnected cables and cleaned up a bad contact. Possibly you have a tube that is acting up intermittently. This is why I suggested using the search function. There may be some scenarios similar to yours that could give you some ideas of where to look for the source of the noise.