Tube advice

In the old, old days, the amplifiers designed by William Zane Johnson, founder of ARC, were well known to run the tubes very hard, and failures were common.  To deal with this issue, ARC was known in those days to "update" their amplifiers quite frequently.  I never knew whether they were trying to convince customers that the newest version of whatever amplifier was "fixed" or what they were really doing.  But tube failure, sometimes catastrophic, was a price you paid for great sound. In any case, Mr. Johnson has long been out of the ARC design picture, and I have not heard in many years that modern ARC amplifiers were particularly unreliable.  If you know what you are doing with bias adjustments, you could source the tubes from Tube Depot, or one step up the scale would be to buy selected tubes from Kevin Deal or Jim McShane, which might cost a bit more but those guys really do test the tubes before selling them.  Even the latter sources might be less expensive than buying tubes from ARC.  Then you can start at bias point where the plate dissipation is at first low-ish and let the tubes break in for several hours before turning up the current, if indeed the tubes are stressed in modern ARC designs. But Tube Depot is a reputable source, far more reliable than eBay might be, for example. Keep in mind that tubes age and change parameters over time, no matter who sold them to you.  So, long term, there are no guarantees regardless of source.

Yes, marktomaras, ALL tubes will require re-biasing once in a  while over time.

Preamplifiers, both linestage and phono stage, generally do not require any bias adjustments.  Nor do the tubes in the input and driver stage of any amplifier I have ever known about.  It's the output power tubes that generally do or do not need occasional checking for bias.  (I say "do not", because some amplifiers have an autobias circuit that takes care of this issue.)

I am not sure I agree that one really "needs" a tube tester to get by with tube equipment.  If you keep rough track of the hours of use, and if you pay attention to how your stuff sounds from day to day, the question of when to re-tube is typically based on subjective judgement of those two aspects.  If a tube tests bad on a tester, it will sound really lousy.  However, tubes can test "weak", but within spec, and still sound fine.  There is no need to change them out unless the sound has gone noticeably off.  The problem with a tube tester, even some of the best ones, is that they test tubes at currents, voltages, and bias settings that may not at all apply to the operating conditions in your amplifier.  This can result in a false sense of security or insecurity, depending upon what the meter says.

Mark, Don't you have an owners manual for your VT100?  If not, it seems unlikely that you could not acquire one for free (check on line for a pdf file) or for a pittance from ARC. 

Dear ADG, Yes, I own a Hickok tube tester, and the number of times it has served me to detect truly defective tubes is near to zero, because such tubes gave away their condition just by listening to them.  It is not that useful for tube matching, either, because it tests all tubes at the same plate voltage and current, which is typically very different from the in-circuit parameters.  Tubes that "match" at one voltage/current setting very often do not match at other settings for voltage, current, grid bias.  Some of the best Hickok testers (e.g., 539B and C) do offer a choice of some of these parameters; those models are to be preferred and are both scarce and very expensive these days.  Further, if you own one, it needs to be calibrated and kept that way.  As an alternative and perhaps to your point, there are available modern tube testers that can actually trace curves.  (I forget the brand and model names, but the internet will tell what they are.) That's the valid way to match tubes. Those are the types used by reputable pros who sell tubes, like Jim McShane and Kevin Deal.  If you want to spend a few thousand bucks on such a tester, that's in a different league from the vintage testers, but are you seriously suggesting that we all need to go out and buy such a device?