Hi , One of my friend is using a Tube amplifier in which there are four K 88 tubes , What will be the life span of these tubes if used with proper care.
No, a "Cayin K88" is a rebranded tube from another manufacturer. And I don't keep any figures in my head for life span of each tube in each amplifier. Circuits that provide for a soft start to the tube as it powers up make more difference than anything else other than bias. Bias is either fixed or user adjustable. How the manufacturer chose to deal with tube bias is something you cannot change.
I accept the fact tubes are not forever, they must be replaced. If you are concerned about tube life, you probably shouldn't be looking at or using a tube product.
My dealer once told me that a McIntosh representative told him that their tubes will last anywhere between 5 minutes and 5 years. I guess what that means is that like anything electronic, if it's gonna fail it'll likely fail right off the bat.