OP purchased his 57 at least eight years ago. So if you’re saying new 57s hum and older ones do not, that doesn’t hold. If 57 hum is random, then hard to tell. I’ve had many 57s over the years, never noticed a hum in any of them. But then, I never use a 57 on a soft source, causing me to have to dime the preamp gain. Usually use them on sources like snares and guitar amps.

But in 29 considerate responses, OP never got back with anyone, so…

So what? I was just adding more information on the subject to an older thread. Wasn’t really replying to the OP. (Edit: Maybe I took this the wrong way from you, since you seem to be very considerate in your posts in general).

I purchased my first 57 last year brand new. When I compare it to the other three new mics that I purchased very recently, there is more noticeable buzz/hum. I recorded one after another in a short amount of time with same placement on the stand, same cable, same preamp, same gain. I have the clips to prove it. After doing this, I went back and forth with the good one and the others, and still the same conclusion. So why does that not hold? What do you think would be causing this?

You’re right that it would not be noticeable with a loud source, like drums or a loud amp. Just think that it is interesting that there is a difference. Regardless, I'm keeping them anyway for the loud stuff…

Same everything, except for changing the microphones. 75 dB preamp gain, full on.
Hard to hear with a mobile phone.

I compared the good mic several times to the others after these recordings, same results. Sounds like a grounding thing…