Buzzing first minute or so, Laney VH100R

[Emetal]

I have a buzzing sound for the first minute after turning on the amp, it is only happening on the distortion channel after minute or so it disappears. I tried changing 12ax7's but it did not help, power tubes neither. Any ideas please...
The only thing I did before this started happening is that I got new 6L6's in. Now even if I put the previous EL34's back in I still have the buzz. Could this have caused the problem or it's just a coincidence??? (Laney has a biasing switch and I'm always using it properly).
PS I tried shaking wires, checked connections, does seem to be problem of that sort.

[Emetal]

Well it seems I solved it, the amp has been on the road this weekend and I have done some fast soldering a moth ago, seems that I had a bad soldering around 12ax7 for distortion channel that got worsen by rough handling on the road. I detached all the connections, cleaned and re-soldered, spent whole night trying out, warm, cold and problem has not returned :-)

[Jazz P Bass]

Hey, someone here would have figured that out.
Not.
Glad to hear that you got her fixed.