Squeel Like A Tube

Now that I have my tube amp stable and sounding great I thought I'd indulge in some tube rolling.

Well I pop in this sold to me on ebay as NOS Hytron CBS branded tube... The sporadic sound can only be described as 1,000 fingernails down a chalkboard while 10,000 eagles screeched at their prey. I snapped this photo right before that noise happened. I must have jumped pretty high. Since this was not a success I put the RCA or Sylvania back in and  all was well with the world again.   

Such a pretty tube..
Such scary noises.