how much tubes influence on the sound ???

When you replace power tubes (the 4 larger tubes on your amp) they should all be of the same manufacture, according to Cary. They will need to have the bias current adjusted when you do this. Cary makes and sells a meter (MD 300?) just for this purpose that simplifies the task (pretty easy to do). Changing the smaller signal tubes does not reqire bias adjustments, and will change the sound of your amp to a slight degree. In VAGUE GENERALITIES, the european NOS Siemans, Telefunkens, Mazdas, will sound tonally neuteral, and more detailed than what you currently have, while Mullards will sound warmer and fuller. The 6SN7's also do not require bias adjustments, Ken Rads will have good bass response, but may be microphonic, the Sylvanias you mentioned should sound pretty nice, Tung Sol round plates are neuteral, detailed and tonally accurate (but good luck finding a pair that isn't worn out). RCA's typically have a sweet midrange. Unless you have a tube tester, or access to one, buying these tubes online is an expensive crapshoot. Many people buy expensive tubes for themselves, use them for a year or so and then try to pawn them off on some sucker who hopefully won't know that he just paid a small fortune for worn out tubes. Buy from a reputable dealer, The Chinese tubes nowadays are actually pretty decent and very affordable if you want to go the cheaper route. In my equipment the smaller tubes last a year or so, and the power tubes last 3 years or so (your results may vary). Tube degradation is a gradual process that you may not even perceive, but you will notice the difference when you retube. Turn your bias adjustment DOWN before retubing and then adjust after you retube. Try to carefully clean the tube pins to remove any grunge first. Do buy a few extra tubes incase some of the tubes blow, on or shortly after installation (a reputable dealer should be happy to replace them for you). Brent Jesse is one such reputable dealer, and there are others, Cary, I am sure would be happy to provide a replacement tube set as well. Tube rolling the smaller tubes and the 6SN7's is fun if your interested in doing that, but not a necessity. Access to a good tube tester is a nice thing to have,especially when buying tubes on-line. I hope this post gives you some helpful advise. Happy Listening,

thanks for all the details on tube u write me ,but i still dont know how much infulence have if i change the all tubes or the 4 power tubes and the 2 pre tubes in the sugesstion that give me see in the top of my first theards ?
and i wanna know if this kind of investment money on my cary amp tubes will worth it bcz this kind of amp is averge and nice and not so good like really good amp to my nines devore fidelity speakers (if i dont mistake) ??
and last thing what will be more good pre tubes to change in my cary : Amperex 7308 input tubes or EAT tubes ??
and where i can find it to buy anew and what the price can u send me link here to see and thinking ???

I've done a lot of tube rolling in various amps.The smaller signal,phase inverters etc.,seem to have some changes in transparency,less distortion,and some sonic characteristics.Changing the outputs had the most change in the amps sound characteristics.I can't speak for your amp,but in general the Chinese and JJ made outputs will be brighter and more detailed.The SED brand will have sort of a lush,and more liquidy characteristic.Its been to long to say what the KT88/6550 most modern tubes will sound like.In general what I'm trying to say is,the outputs will give you the most different sound between brands.For a different sound,maybe try the outputs first.

since you are new to tubes I suggest you do not change any tubes until you have listened to your gear many, many months, then consult the manufacturer and have them tell you what tube changes influence the sound the most and go from there. Do very gradual changes. Tubes are sensitive to unstable power from the wall and I'd suggest a device to lock in the current to 120 volts.
Larry

I believe Israel has 230 volts.Somebody from there may give an idea as to how their voltage and quality is in general.A lot of SS gear can vary with different utility
fluctuations.