new amp vs old amp

Hi Ampzilla; Sean has a good list of possibilities above. One I would add is becoming very, very familiar with a particulat recording with one of the amps. I mean get so familiar that you are almost sick of it-- then put in the other amp and see what you think. If the music still sounds the same, I would guess there is a weak link somewhere else in your system.

At some point you need to become totally confident in your hearing and hearing perception(s), ie maybe they really do sound the same. Although I would guess that there should at least be a difference in bass character/quality. Good Luck. Craig.

I'd like to share my expierences in changing audio pieces or cables. This may seem strange but I've run across this many times. On occasion when auditioning a different piece of gear or cable I would hear either subtle or no difference. But when I would put the original piece or cable back in my system is when I would realize the different characteristics of the piece or cable that I had taken out of the system. This may not seem to make any sense but for me it has become part of my auditioning pratice. Perhaps I don't have the golden ears others have, or I wish I had. ----->Ray

Ampzilla: your "brief A/B testing" makes it seem as though neither piece was warmed up thoroughly. By "thoroughly warming up" I mean powered on for at least 30 hours.
In solid state equipment it takes that long a time for the power supply regulators to attain thermal stabilization; any comparisons prior to that may be preliminary at best.

for the record the rest of my system,aside from the new and old amp!are amc cd8b,p.s audio 4.5 vandersteen model 1,and also some tannoy proto j's.im about to replace the p.s audio in favor of an older preamp,believe it or not.im going to buy a thalia,well see what happens,thanks for all your helpfull advice!!!amp.

All of the suggestions above are good ones. I would like to comment on the Dynaco ST-120. It was a great amp with performance way beyond its price and time. I owned one in a second system of mine in the 70's and recommended it to my cost conscious and tube averse friends throughout the 70's.
However, sound wise you should be able to hear it showing its age. If you could borrow someones tube amp and if you still don't hear a difference I would say that you have some rather serious limitation in the rest of your system. On the otherhand, while I don't know the Acurus, maybe its not that great an amp.