Hi Wyn, Thanks for the comment on my AD797SQ purchase. I frankly don't not have the technical electronic's knowledge to check them out. I am quite certain that as they are from China, they are copies, but what surprised me is that they without a doubt they sounded better. Even more strange was that I was assured by the original builder that he used genuine parts!!.
Also what surprised me was the reduction of noise from the unit, very strange.
I recommended them because I know that some builders, retired like me, may not have the funds to buy genuine AD797's & when someone is contemplating building the kit, cost is for many a major consideration. Without a doubt if I had had to by genuine 797's I would not have built the kit, not willing to take the risk. (my kit building hit rate is about 2 duds to every 1 success), No matter how many good reviews the product has had people are often a little reluctant to shell out hard earned money, especially if you have to live on a tight budget.
I think they should be considered like the Russian output caps. In theory they should not sound great, but they do & so do the SQ op amps.
Cheers Derek