As of a couple years ago, Rob Gillum still had CS2.4 upgrade “kits”. Basically, the Clarity Cap SA coax feed caps plus polished outriggers. Perhaps he also has outriggers for other models?
Of course, anyone wanting to upgrade their 2.4 can now do better than the Clarity SA which dates back to circa 2008. The SA caps have twice been upgraded (CSA is current version) and Tom Thiel hinted that an even better version is on tap. Of course, you probably won’t be able to get the full 14 and 28 uF in single caps (which is highly desirable over the 13+1 and 27+1 found even in Lexington-sourced boards).
