Jadis DA60

I used to own an Orchestra Reference, and currently have a DA30 and DA60. In my experience, in addition to being some of the most glorious sounding components, Jadis integrateds are as reliable as anything on the market. In fact, in my system, they've been flat out bulletproof. I've often heard Jadis transformers are warranteed for life, so if you bought the amp new, there should not be too much of an issue for you.

Since Jadis integrateds fuse each output tube, the statement of your technician doesn't seem especially plausible. In my JOR, I had a fully shorted KT90 output tube that caused absolutely no damage to the amp whatsoever. A bad tube would blow a fuse long before a transformer.

I realize this is not going to come across well, but my guess is that the problem is you. Do you have a load (loudspeakers) hooked up to the amplifier at all times? Running a tube amp without a load is a surefire way to blow the output transformers. The vast majority of tube amplifiers that have been built since day 1 have never had a problem with their transformers despite seeing a lot of bad tubes - look at all the vintage Dynacos, Fishers, Scotts, etc. that can be brought back to life even after decades of neglect.

Jadis DA60 can use any tube among the EL34/6CA7/KT77 and 6550/KT88/KT90 variants. Jadis says it themselves, and I've done so as well in mine with no problems whatsoever. Why do you need anything more than what the people who build the amplifier have to say on the matter?

For the record my preference is EL34 first, KT77 second, then KT88, but that's why they make vanilla and chocolate. Use whatever sounds best to you knowing that the amp will play beautiful music with no issues whatsoever with your choice. It's difficult for me to think of a better, more musical amplifier than the Jadis integrateds.