Isolation for tube amps

As you mentioned, another room is the perfect solution. All else will disappoint. However, building a screen of Tandy ( Leather Stores) 'pound o board' is a cheap and very effective solution. The only more effective is lead wall paper, toxic and expensive.

Wow gentlemen! thank you for your amazing insight. That's a lot of information to chew on. I really appreciate you all taking the time to put together such thoughtful and thought provoking responses! This is one area where I think the industry is coming up short on. I plan to continue expolring this vibration/distortion relationship. Thanks again for all of your input - very good!

Another thought on the subject.....I used a RS dB meter and sampled different frequencies around my room. I found that some areas had much lower sound levels at different frequencies than others. I had to use longer ICs, but placed my rack at the lowest "loudness" position. I also placed the amps on stands nearer the midpoint of the wall behind the speakers because this was the "quietest" place. I then mass loaded the mono amps and used points on the bases through the carpet to the concrete floor. Does it help? I think so, and it cost nothing.