Weird noise from Crack amp

[Exist1214]

I've been having a very odd noise in the audio signal coming from my Crack amp.
I uploaded a .WAV file that I hope accurately shows the problem.
This noise happens when music is playing, when my volume is turned down all the way, and even when my DAC is turned off.

Does anyone have an idea about what is causing this? Thank you!

Edit: The forum does not allow me to upload an audio file. Hopefully this works: https://voca.ro/1dwiE9lyIXAK

[Paul Birkeland]

Can you tell me about the products you used to build your kit?  Solder, flux, etc? 

There is a remedy stickied for ground noise from computers and USB powered DACs, but that's not necessarily consistent with the noise I'm hearing from your kit...

[Exist1214]

Can you tell me about the products you used to build your kit?  Solder, flux, etc? 

There is a remedy stickied for ground noise from computers and USB powered DACs, but that's not necessarily consistent with the noise I'm hearing from your kit...

I used a 63-37 Sn/Pb solder with a rosin flux core.
I'm not sure where to even start with troubleshooting. I've not had this issue with any other audio devices 

[Paul Birkeland]

Does it happen in both channels?  With nothing plugged into the Crack and the volume pot turned all the way down, do you still hear that noise? 

What I heard in that noise was a little reminiscent of what I've heard from plumbing flux being used on a build, but it may well end up being USB ground noise or some kind of interference. 

[Exist1214]

Does it happen in both channels?  With nothing plugged into the Crack and the volume pot turned all the way down, do you still hear that noise? 

What I heard in that noise was a little reminiscent of what I've heard from plumbing flux being used on a build, but it may well end up being USB ground noise or some kind of interference.

Yes, it happens with the volume all the way down and with nothing connected to the amp.

[Paul Birkeland]

Does it happen in both channels?

[Exist1214]

Does it happen in both channels?

Sorry I missed that - Yes it happens in both channels.


Hmm, just noticed something weird. I issue is normally intermittent...it's not constantly making the noise. Sometimes just for a few seconds, sometimes for minutes at a time.
I found that if I gently pull the smaller tube towards me or push it to the left, the noise immediately comes back. 

Could this be a bad tube? Bad solder joints? Unfortunately I was thinking that just re-inserting the tube and making sure it's fully seated would fix the issue, but it didn't.

[Paul Birkeland]

If you tug on both black wires on the headphone jack, is one of them not well captured by solder?

[Exist1214]

If you tug on both black wires on the headphone jack, is one of them not well captured by solder?

They appear to be pretty well captured by solder

[Paul Birkeland]

It is very likely that you have a loose solder joint.  Wiggling the 12AU7 and hearing the noise change would tend to support that hypothesis as well.

[Exist1214]

It is very likely that you have a loose solder joint.  Wiggling the 12AU7 and hearing the noise change would tend to support that hypothesis as well.

Ok, maybe I'll try to reflow a bunch of the solder joints tonight.
Thanks

[Doc B.]

Also try cleaning the tube pins. A scotchbrite pad can do the job.

[Exist1214]

Also try cleaning the tube pins. A scotchbrite pad can do the job.

The pins did not look dirty or oxidized, but figured I'd give it a try before getting out the soldering equipment.
So far so good, thanks! I'll try reflowing the solder joints if it comes back 

[Doc B.]

That's the nature of tube pins. They often have a sort of dark finish to them even if clean and, conversely, some can be a little oxidized even if they look very shiny.

I put every tube in a pin straightener as I test them and that is usually enough to clean them up. If they a seem a little suspect once they get in the tester I will usually hit them with a Scotchbright pad and then test them again to be sure they are 100%.

The oxidation can come back fairly quickly depending upon the environment. It's worthwhile cleaning the pins on tubes once a year or more often, just like it helps greatly to clean all interconnect and power cord connections a couple times a year.

[Exist1214]

Good to know, thanks for the details!