Tube Failure question

Thanks Facten. 

Call Kevin Deal at Upscale Audio in LA. He’s the USA importer for PrimaLuna and may be the North American importer. He’s one of the most knowledgeable guys in tubes in general, especially every model of PrimaLuna. I used to have the PrimaLuna Dialogue 7 monos. I had a bad tube in the first year or so and then went 4-5 years trouble free. Trouble free and magical, I might add. I switched from KT88s to KT77s. A bit less power but a touch more magic. Be careful of asking for more power as the PrimaLunas are not really high power amps. I assume you bought them to match with your current speakers. Without doubling your power you’ll really not gaining much by adding a few more watts and again you may lose a bit of musicality. Someone here said that PrimaLunas run tubes at very low power, that’s very true as now I moved up to a more powerful KT88 amp and although it has more bass and detail, it is definitely a tad less musical than the PrimaLunas in triode mode with KT77s but now I buy 4 new KT88s every year. It’s too bad I couldn’t keep both because my current amp is amazing, but there are days when I look in the for sale section for some Dialogue 7s. Call Kevin. 

I didn't realize you had mono amps some great suggestions above. Is the sound in just one or both channels?