What does anyone know about this amp ?
Is it a recommended item or to old to be useful ?
DUP actually could be useful here, but here's my shot at it:
It's a modified Dynaco 400, 200W per channel. I have a review of it from Audio Amateur in about 1979, and they thought that it was a good amp, but too expensive for what it was (a relatively minor modification of a moderately priced amp). Solid state, pretty good for the era, but no Krell. If it's cheap enough, it might be a deal, but I'd be willing to bet you could get a more modern Hafler with similar power specs and better THD for about the same money. I can't say I've ever heard the Van Alstine mods for the 400, but an unmodified 400 is a perfectly respectable amp.
IIRC from the review (and I'll dig it up if you want me to-- I have AA's 70s CD collection, which is fascinating reading even for non-tinkerers-- it includes tests on both the modified and unmodified 400), the unmodified Dynaco 400 was a class B in Stereophile back then.