I loved my 8038 generator as at the time i was just fooling around with audio. It was great for me at the time. I have a 2206 chip around but never used it because the bandwidth bites. These days a dedicated DSP based wave generator is just phenomenal with an output frequency of 0.01Hz to 40MHz !
There was another chip, similar to the XR2206, that was put out some years ago (maybe 10 or 15) and i was after one back then, but found that they had discontinued them too. They actually went up to 20MHz sine/sqr/triangle which aint bad. I wanted one but got to looking for one a little too late so i could not get one. This chip was made in a similar fashion, with the symmetrical non linear multi transistor wave shape circuit seen in the other chips, but faster.
I also wanted to build one from scratch but never got around to it. A handful of transistors would do the wave shaping, and the circuit could be tweek'd for optimal wave shape. One of these days maybe i'll tackle it again. BW should to up to at least 10MHz with common parts.
For now i intend to use the DSP chip, which goes up to 40MHz sine, but have yet to get that into a box with all the knobs and stuff
It is very interesting to hear other people talking about these chips too. It is hard to believe that all three of these chips are not made anymore. I would think there would be some use for them. Maybe the problem was that the sine was never that good. Not bad, but not good enough for real audio work and after all that's what a lot of the sub 1MHz chips would be used for i would think. That puts them in a niche that just isnt there. Who wants a chip that puts out a rough sine wave. That's my guess as to why they disappeared anyway. Still, the discrete version would be very interesting to build from an analog hobby viewpoint. I'd love to see how good we could get it. These days you can get multi transistors on a chip too, so the parts count might not even be that high, except for the multitude of resistors required.