I own JL-1 Monoblocks and installed EH KT-88's about a year and a half ago, not only do they sound much better than the stock 6550's but they seem to last longer.
6 responses Add your response
I too am running with Winged C's (in JL-3's) but have also wondered what benefits KT88's might bring as they were wonderful in the ARC VT130 amp I had several years ago. With the CAT amps, I would be more concerned about reliability and longevity of the power tubes. There is so much to gain with changing the small signal tubes here. Send me an email and I can share with you some of my latest findings. Another CAT owner has also provided me with some tips that I will try out here soon.
Ubglub - I have not had two sets of 6550s to compare the sonics of one set to the other. When the Svetlanas started to fail, I was able to get matched sets of Winged-Cs. This was after approximately 2 years of playing music 20-25 hours a week. Once the Svetlanas were failing, I threw the rest in the trash as failed tubes can do some destruction with these amps. One tube failure on a JL-3 here was not pretty!
Like Ken Stevens wrote to me, if you have one or two bad tires, do you just buy one or two more or do you replace them all? In this case, power tubes are the same....when they start to fail, it's time for a whole new set.
Concerning longevity, there's no way to know until I have a comparable amount of time on the C's as I did with the Svets. After a couple months on the C's now, no premature failures so it appears to be a sound set. Only time will tell. And with the amps recently getting an update with new sets of resistors to better handle tube failures, I feel good about how things will be when a tube ultimately fails. I understand the updates to my JL-3s is now standard in all later amps; mine were one of the earlier pairs. But I do not have the Black Gate Cap updates....the JL-3 Sig MK II is that model. Mine is simply the JL-3 Sig.
Between the time my amps were being updated and me ultimately changing to the C's, a number of other refinements in my system occured....a change from Purist Dominus to Stealth PCs, the Aesthetix Io was updated and some newly discovered magic with tube rolling in the Io and Callisto. From these changes, my system was much improved by the time the JL-3s returned so there was no way to know the changes brought on by a different set of 6550s.