Sorry for pestering you with stupid questions. Here are some more:
What does b/w of 7GHz mean?
Bandwidth of 7GHz allows one to see all of the high-frequency in the signal.
What is the sampling freq of the scope?
Is there any way of reducing the noise on the squares?
The noise on the square-waves is of no consequence. The only thing that matters is the rising edges.
Would the use of
discrete components (transistors, tubes, chokes, etc) rather than chips help?
You could probably filter out the noise by using a slower responding regulator and maybe slower logic family, but the jitter would increase dramatically because the risetime would slow.
Do you think it would be audible?
Yes, it would cause smearing of the image due to increased jitter.