Hi,
After building the Crack this June, I've had a hiss/white noise/static on the left channel. This is there regardless of the volume. I was initially able to avoid or reduce it by slightly tilting the power tube, and if I remember correctly, it was usually slightly tilted to the left while still pushed into the socket as much as possible. When it was not tilted all the way, I noticed that any disturbance or slam into the desk made a noticeable sound or thump in the audio signal. When doing the chopstick test, I was able to replicate this as a small disturbance or impact on the plate caused a thump in the audio signal. Additionally, I noticed that on power up, a series of small, quiet, electric-y pops occurred and lasted for about half a second.
I looked initially at the octal socket but was unable to find anything that to my untrained eye was wrong, and using the chopstick test was otherwise fruitless. I doubt this is an issue with my DAC and have used different solid-state amplifiers without issue with it. I tried using different power and input tubes and the issue, while disappearing on the first plug in of a new power tube, persisted after taking out the tube and putting it back in. I did notice, however, that with the new tubes the thump when a disturbance occurred does not seem to happen any longer.
I should add that I did switch out the potentiometer that the Crack came with with the RK27112A00AK on Mouser (Alps Blue Velvet).
All voltage and resistance checks came back in range of the manual, and I've attached pictures. If something is unclear, I can attach more.
For whatever reason, when I tried posting with images, the site gave me an HTTP500 error, so here is the link to an album of images. {https://}photos.app.goo.gl/bcxLzP9hRgifY73dA
