Interesting, Leo - particularly about the valve rectification. Does that have the tendency to make the sound 'softer'?
One of the things I like about the Yaquin is that it has the 'drive' and 'dynamic impact', for want of better expressions, of a solid-state amp, and yet also the subtleties and magical sounding midrange of valves. Maybe that's because there's a fair bit of solid-state in the Yaquin!
I can tell you though that simply upgrading the Chinese valves to Russian ones, from Electro Harmonix and Svetlana, significantly elevates its (already excellent) performance. As it is with the new valves it's easily as good as most £3k designs, which is remarkable when you consider that even with upgrading the valves I've spent no more than £500 including its original purchase value!
So ok, let's say you were modifying the Yaquin and had £1500 to upgrade it (which is the most I'd spend) which aspects of its design would you target first for modifying/upgrading?
I definitely want to do away with the internal circuit boards and fit point-to-point wiring, as I believe there is a 'signature' with printed circuit boards that you don't get with hard wiring, so apart from that, what else would you suggest doing?
Marco.