Actually Forte Model 4 is the Class A version of Model 6. (Not Model 5) I used to own a Model 6. I believe it's a Nelson Pass design. There was an article in Stereophile about the Model 4 and 6. Basically, he designed the Model 4 in pure class A, and the company wanted to put out a product with higher power rating, so he converted the Model 4 to Class AB to give it a 200WPC output.
FrankC
FrankC