Is upgrading stock tubes standard proceedure?

I am with you Phaelon. After all, I do change the tubes myself. And yes, I do have better tires on my Audi. I even upgraded the T tires to H tires on our old Camry when the T's wore out.

The language manufacturers put in their owners manuals is just CYA to put us on notice that they do not warrant owners opening the case (during the warranty period at least). They all know we are going to roll tubes. I'll bet even Bill Conrad and Lew Johnson changed out the tubes at home.

We were discussing the Blue Circle DAR Hybrid Integrated amplifier with Gilbert Yeung at RMAF in October. He offered a customer to make one custom with the tube mounted upright though a hole in the case, so the tube could be swapped without having to keep opening the case.

There are lethal voltages present even well unplugged in some components, safety comes first!
Manufactures are well aware how careless some people can be.

For sure some equiptment respond favorably to select vintage brands of vacuum tubes however some do not as Tvad and Mrtennis point out.
They know what they are talking about...

There are a few modern companies that take the time and use the quality of materials that made MOST of the NOS tubes so good. The vast majority of those manufacturing tubes currently, are doing so strictly for fast profit, cut corners anywhere and everywhere they can, and their tubes sound like it. I got back into tubed gear/NOS tubes 18 years ago. I've yet to find a piece of equipment that did not sound more like live music with the right NOS tube upgrade. Here's a list of the companies that are producing tubes that can compete sonically and quality wise with the old stuff. Price some of the pieces and get an idea of the cost of quality manufacturing nowdays:(hhttp://www.kraudio.com/ttp://www.gcaudio.com/cgi-bin/store/search.cgi?cat=49) (http://www.gcaudio.com/cgi-bin/store/search.cgi?cat=49) (http://www.westernelectric.com/products/300b.html) If the signal passes through a tube, it WILL affect it's sound. There's no such thing as a tubed circuit that is not "tube sensitive", in this regard(the tube being the most "active" component in the circuit). Even the rectifier will have a sonic effect on the sound of most tubed equipment, although it's not directly in the signal path.

An extra "H" got in that first URL. Here's a correction: (http://www.kraudioproducts.com/Kr/ProductMain.aspx?CatID=13)

I just place my order for these two tubes Mullard CV4004/12AX7 to be used in my VTL 7.5 preamp. I heard noting but good things about these tubes... I view purchasing NOS tubes like purchasing a rare wine some may like it and others may not.