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Paul, there is a number of inaccuracies in your post.

Paul S wrote:

Lots has been written already about tube replacement, but I want to mention my recent experience when replacing the 6C33C output tubes (V2).  I had the previous tubes in for only about 1 year; in this case I estimate about 300 hours, although I do not keep a log.

One year is a normal life expectancy for 6C33C, those 300 hours sounds a little too short.  I would say that a normal 6C33C driven at sub 50W should serve 800-1000 hours and then it might be replaced even if it works fine. Sure, being a Russian tube and partially as low QA as 6C33C it might do whatever she wants…

Paul S wrote:

I got the previous tubes from Lamm because I could not find anyone else at that time who could/would match them for gain.

It is extremely simple to do yourself – it will tale a few minutes.

Paul S wrote:

Lamm now wants 192.00 USD for a pair, so I  shopped harder.  My new ones are from Ken Chait.  We'll see what happens.

I do not believe ANYBODY do tube matching, particularly the 6C33C. They all BS-sayer and 99% of them know nothing about 6C33C. How that Ken Chait match them? I would love to mock his assurances and his warranties of “matching”. Lamm does test and match his tubes, those his price of $192 sounds to grotesque, particularly knowing that he buys then in Novosibirsk for $5 each. Now, the sad truth is: the 6C33C for ML2 should not be matched at all. Well, they should be matched by gain that could be done by 8 year old child. It is SET amplifier not PP amp, what the hell we are talking about matching? Even the bias selection is not necessary in ML2 as the V2’s bias resistor is wide enough to accommodate wide offset of 6C33C’s bias.

Paul S wrote:

So, who knows how much additional "service life" the previous V2 tubes had/have on them?  It's hard for me to believe that the V2s only last 300 hrs, although I might only be getting 100 hrs from the stupid 6N6Ps.  Anyway, the bass started to go, it sounded like V2, and new output tubes got it back.  I will continue to use the "old" output tubes as voltage regulators (V1), as Romy suggested, since it has worked fine so far.

The 100 hrs from the 6N6P sound too strange and not credible. Also, when the 6C33C doing south it does not loose any bass. Paul you need to revise your views about the dying tubes…

Paul S wrote:

But the main thing I wanted to pass on here is to remind other ML2 users to be careful about bias settings when installing new V2.  My old tubes had just checked at 185V/28mA, and I was only reminded to check the new tubes when I could smell them.  At that point they were 64mA!  No harm done that I can tell, but I'm glad I stuck around rather than leaving the room while the amps "warm up" for 20 minutes, like I usually do!

Most likely it was not 28mA and 64mA but 280mA and 640mA.  I have written many times that a new 6C33C should be properly broken in. Read about the “start up gap” in the “The short "6C33C Survival Guide":

http://www.romythecat.com/Forums/ShowPost.aspx?PostID=6140

When you installs a new time in ML2 you need to turn the plate current regulator all the way to the left. Install the tube (it will be 10mA-30mA), let this tine to burn like this for 30 min. Then set the plate current 150mA and let the tube to experience 3-4 times a full cool down and then > 30 min. After then the 6C33C will loose most of it “start up gap” and might set to it’s cruse current after it was buried more then 30-40 minuets.

It is shame that Lamm never explained in his manual to his customers how to properly prepare the new 6C33Cfor use. It is obviously that he prefers to charge $192 from his naive customers in order to kill the “start up gap” in his house.  Interestingly that this strange Lamm’s “caring” hurts him very aggressively and I have no idea why he never learns. I know/knew ton of ML2 owners who avoid buy tubes from Lamm just because the ridicules price. I am sure if Vladimir open his mouth and explain to people the satiation then people might not feel that he juts fucking them up. Well he does but not in the moment that people know.  The very same took place with Lamm L2 preamp. Over the years I say to people to replace regulators and the rectifier but the freaking Lamm kept saying “good for over 5 years”. The result? Tone of people have sold the L2 preamp because it did not performed well due to the dead tubes in PS. In fact, in 2004 the avalanche of the people who were getting rid of L2 was so high that Lamm was forced to make a public warning that the regulators should be replaced after one years (in realty 2-3 months, though I have see that the sound of L2 went down after 2-3 weeks because of the 6C19P). Funny is that Lamm deal with 6C19P for 30 years and well knows what it going on – he juts do not give a shit. Well, so did I and other people when we get rid of our L2 preamps…

I have no idea why he behaves as he does, well at this point I do not care as I have my answers.

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