Tube Substition M100 Mono Block

[TheMuffinOfEvil]

So today I opened the sealed mono blocks I found. The tubes weren't even seated, still packed in little cardboard boxes. All but one 6550 tested out good. So now I am scrambling to find a 6550 to see if this other amp works, (first one powered up slowly but works and sounds great) and people are telling me I can substitute in a KT88 tube. Is this true, or do I need to order and (curses) wait for a 6550 to arrive.

[JPrest]

Careful , I just had to sent my VT100 into ARC because I was messing around with the 6550 tubes with the bias turned up to normal, of course, I blew the resistor next to the tube I had just substituted. Turn down bias (little blue square with white turn dial) then bring up slowly with voltmeter monitoring balance and draw. See instructions on web.
I found a YouTube video for mine.
Good Luck great equipment, I also have the Classic 120's similar to your M100 only 8 6550 each.

[TheMuffinOfEvil]

Was acctually just about to post and ask if someone could give me a Bias walk through for my amp. I have never done this before.