a few weeks back i made a bulk order of JRC4558D dual opamps (i think i have about 150) but i see these things on ebay for massive prices.
what am i missing?
Nothing. It's all hype.
I believe Jack has an excellent article on 4558 legends and myths at muzique.com
The JRC4558 is once again in production under a slightly different name, smallbear has the for peanuts. You can use almost any dual opamp and just pick the one you like - most of the time you won't be able to find any differences between them, though.
Apparently you lack the gullibility gene, and as a result have a serious deficit of stupidity, due to an overabundance of common sense....it's a chemical imbalance. If you want a cure, I am sure many people will be happy to come to your home and hit you upside the head with a large and heavy blunt object. It may even be covered by your national health plan.
*ANYTHING* that was ever originally built with a 4558D was designed around a chip that was cheap, easily available, and "good enough". There is nothing exotic about them, nothing particularly rare about them, and I think I can say with confidence that their sustained production has very little to do with the TS-9 re-issue market and everything to do with their widespread use in a large variety of products *because* they are cheap, easily available, and "good enough".
Some of us like these 'good nuff' chips best for Fuzzes etc.
4558's seem to make it to the finals in most of these chip 'shootouts'.
Probably because of the things Mark said, they do seem to "Go all to Hell" in a distortion circuit nicely, if your into that sort of thing. Of the 20 I have tried, the differences border between fairly subtle to "did I really change the chips". Changing diode types and numbers is much more noticable. 8)