I'm not a big fan of these amps. Check to see if the units have the old grey Mepco Filter caps in the center of the amps. If so, they must be replaced. The Classic 150 followed the M300. It's basically the same amp except the CL150 has a triode connection at the output tubes. It is Fet transistor except for the outputs making the amp ARC's first hybrid amp. The M300 was later connected triode at the outputs because of tube issues at the time. Philips/Sylvania had stopped making 6550's and the only tubes that were available at the time were awful Chinese coke bottle 6550's which failed often. The filament stayed lit but the tube would fail to conduct. The tube that followed, the Chinese KT-88, was just as bad. Since it was easier on the tube to run the 6550 pentode as a triode, the CL150 was born. M300's that were turned into CL150's have larger power and output coupling transformers. Otherwise both amps were the same.
Audio Research Classic 150
Fellow audiogoners, I can't find anything about this amp anywhere on the internet aside from a few technical details. I found some opinions/reviews on the Classic 60 but not this pair of amps. I am considering pulling the trigger on a pair but am nervous because of age of these (ca.1989?) Is this still worth pursuing? Are these good amps? (Sorry for the sweeping generalization-type question but - I'll take any opinions at this point) Thanx in advance.