Heeeelp New used BAT Vxi3 - Hisssssssss

Hi tubes can have issues even though it measures ok. I agree with the poster above, if the issue is in one channel, swap tubes (turn off first!! And maybe let cool down a bit). If the noise moves, it's that tube for sure.

This is also normal for tube lovers-tubes can act funny occasionally, especially after shipping or power off/on...

Sometimes it can be a dirty tube socket (the ringing however hints at a bad tube)

If the problem follows the tube when you move it, I would have to say the tube is bad. Also, in line 3, it sounds like there is a hiss, as well, that is not following the tube. If that’s the case, I would check the settings on the components. You may have to switch between single ended and balanced operation. Make sure that both channels are set to either SE or BAL, and definitely try both settings. Also, you need to make sure that your cables are balanced, as well, and don't just have an XLR connector.

Preamp and Phono tubes, because of the gains involved, should always be tested/certified, "Low Noise", "Preamp", "Platinum Grade", etc. Hiss(tube rush) may result otherwise. The other mentioned noises, during play or warm-up, are not normal and indicate problem tubes. Often one can locate the errant tube easily, by tapping gently with a pencil eraser. there are many tube testers that do not apply full operating voltage to a tube being tested, or only test for transconductance, shorts and gas. Internal circuit problems often will not become apparent, until the tube is actually in use.

The max gain of the Parasound is probably higher than ideal for the pre-amp, so try turning it down via the gain knobs on the back of the amp (nice feature!).

Speaking for myself, it's OK if I can discern the hiss at the listening position when flipping the mute switch on and off, but I don't want to be made consciously aware of it, if that makes sense.

The audibly crackling tube needs to be replaced if the noise persists.

BAT ships the basic 3iX with very quiet Electro-Harmonix 6922EH tubes (these also come in a version with gold pins, which I don't have any opinion about). Mine also shipped with J/J 6V6 tubes (the 2 bigger ones). I'm not sure how much the 6V6 contribute to the hiss.

"The Tube Store" has a convenient 3iX tube replacement package with all Electro-Harmonix tubes for $90.

You could also try Jim McShane (mcshanedesign.net), who has a very good reputation with tube users. Explain your situation, and he can select the quietest tubes for you.