Rob - this wire issue deserves more fleshing out.
CDA101 is 99.999%CDA102 is 99.99%CDA110 is 99.9%There are other requirements for each gradeAnnealed Copper is less conductive than these grades, which are all Electrolytic Tough Pitch-at the pinnacle of conductivity for hardness.
Regarding ERSE's CDA101. As you know, I've been playing detective to study what would have been obvious at Thiel Audio, which I left in 1995. I have good inside sources, most of whom either never knew, don't remember or don't have access to relevant records.
What I know: AcoustaCoil (later absorbed by ERSE) produced all our CDA101 coils since 1978. State of the art. When trying to get a definitive statement from them regarding their website claim of CDA101 - I didn't get a straight answer. I got diverted to Barbara in sales (who seems to run the show) who went to engineering who came back with the answer a couple weeks later of "ETP / CDA110-special. Now, let me float some conjectures.
ERSE along with ScanSpeak and most everyone else makes most of their world goods in China with FST being a prime source. My conjecture is that the Chinese wire plants are using CDA110-special and that is why the "answer" to my query came back that way. However, I also know that ERSE makes their custom coils for the American Market at their Cleveland plant. My conjecture is that those coils are indeed CDA101 as stated on their website and consistent with our long history with them.
I can't prove that and really don't have the will to drill down - there's only so much time. But for discussion, let's suppose that's the case.We know that the 3.7 XOs went to FST some time around #500 (no hard evidence yet.) We know the resistors and caps were CYC clones of Thiel's ERSE and Solen originals. We know that Jim "approved" them. We also know that direct comparison of those components in the 2.4 illustrated the original Thiel parts being "better", as discussed previously in this thread. We know the FST coils look decidedly inferior to ERSE coils. I have not yet made a direct sonic comparison. Beetlemania may have directly compared coils to coils - I don't remember.
We also know that all CS2.7s were made in Lexington with original parts including ERSE coils and resistors, Solen caps and Masonite boards. It is possible that the reported fluidity and grace of the 2.7 might be in part due to that factor of All Lexington build practice.
To the other point of foil and/or stranded - I have used some ERSE foil coils, but not directly compared to (known to be CDA101) ERSE coils in the 2.2. I have not used stranded. Regarding both foil and stranded, they make a difference in resistance and capacative reactance - so those changes would have to be compensated in the XO. I do not yet have the chops to make those compensations, so I haven't gone there in my development work.
That's about it for now. TT
