Thiel Owners

@tomthiel Interesting that there are 3 iterations of the CS2.4 XO. It appears that, other than the Clarity SAs on the coax feeds, my SE version has the lowest parts quality of the 3! I suppose the sandcast resistors are equivalent for each iteration.

 

@holco, unless you opt for a full Tom Thiel-style XO rebuild, which is my plan, I wouldn’t change much else on your boards other than the resistors. Your woofer board has better caps and coils than my FST-sourced boards. I would replace the resistors with Mills MRA and call it a day.

 

On the coax board, I would replace those resistors as well, maybe try to figure out a way for them to breathe for better cooling under those big Jantzen caps (perhaps a thin aluminum bar underneath them to draw heat to the sides?). It is highly desirable to replace those 100 uF electrolytics with MPT-type (Erse PulseX is a good option that won’t break the bank) but it will be really tough to fit those on your PCB. I suppose you could just replace those with fresh electrolytics of similar size. The only other thing I might consider is adding a high quality bypass to the 43 uF subfeed. The cap itself is labelled as MPT type (might be a Solen?), so already good quality. But you might try a ~1% bypass. I am going to use a 0.33 uF REL Multicap bypass with that cap (planned as a Clarity CSA 250 V). Cornell-Dubilier 0.1 uF is also worth considering for a bypass. You might even experiment with 1% bypasses on your Jantzens if you’re really adventuresome.  

beetle - good advice.
Regarding your 2.4SEs, the evidence suggests that the original boards made in Lexington were Masonite PtPoint. Perhaps after Jim's death (2009) Lexington changed to PCBs with the same traditional parts. (I don't know when that change happened, but ERSE had those PCBs for sourcing parts before China. Many folks say the PCB per se does not reduce sound quality. Your SEs came from after XOs were sourced from FST in China with CYC parts, including some downgrades from Propylene to Polyester (T). It seems that those parts were supposed to be clones of the extant parts, but sources say the verification is weak or missing. We are assuming the unverified Chinese parts are of lesser quality. Despite the unknown parts quality, including wire alloy, the coils are not tightly wound, which results in squirm losses.

Regarding sandcast resistors, you have heard and I support upgrading to Mills. However, I know that the Lex sandcasts were ERSE which we know to be best of form. But resistors are great bang for buck, so why not upgrade while you're in there. 

Excellent caps, resistors discussion- Beetle and Tom.
Thank You for so much information as it benefits us all.

Happy Listening!

tomthiel... 

I reside in Lake Grove,  N. Y.   Very close to Stony Brook University.  Again, free for pickup only. 

I haven’t looked at them in a while but I remember the serial numbers were sequential.  

I havo bought an LCR meter so it will be possible to check out the coil on the woofer board, now I only need to find the time to do it.

I have planed to change the PCB for bigger ones, so there will be room for the parts to breathe ;-)