6C33C-B tubes


I have 35w p/p Class A monoblocks which use two 6C33C-B tubes per unit. The manufacturer recommends a bias setting of 150mv. Before biasing (once a month), the tubes' measurements rarely deviate more than 10mv over/under the 150mv. Over the last year, I’m guessing that they’ve been in use for about 1000 hours. I have no idea what their expected lifespan might be. So far, biasing is still relatively easy. The manufacturer is no longer around to answer any questions. So, here’s a few for the Audiogon community.

1) For those of you using 6C33C-B tubes, are you able to guesstimate their lifespan in your amp – in Class A operation?
2) Generally speaking, how necessary is it to bias exactly to the manufacturer’s recommendation – in this case 150mv? Is there an acceptable tolerance +/- %?

Thanks! P.S. I’ve been replacing the sockets once a year.
steakster
I was able to download all the PDFs from the link Tortilladc provided earlier. If you want the results just shoot me a PM and I'll try and attach the pdfs in my reply.
link is still live and working. now it's time to read up enough to understand the results!
I bought 8 tubes from a guy in Russia in early 2012. They arrived in unopened original boxes. I sent them to Parts Connection for testing. As I recall they had a special setup for testing them since they sell the 6C33C tube.

My Quicksilver 50 Watt 6C33B Triode mono amps are biased at 65ma per Mike Sanders recommendation. The 6C33B tube is no longer made, so all of them are NOS.

Here’s some good information on the tube from Romy the Cat.
http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=6140
Check the New Sensor site and click tube specs/FAQ, there are some great info here. I would recommend buying from a person who gets their matched tubes from them. I have BAT tube amps and get matched 6C33B tubes from New Sensor, I re-match the tubes in the amps before using them, the closer they are matched the better they sound. With age they drift apart, so I normally rematch the pairs every 6-8 months.

Another aspect of tube life could be due to the age and quality of the capacitors, I've noticed that when I upgraded the electrolytic caps in my unit, tube life has increased.
Hi Btselect

How much did New Sensor charge you for the 6C33C-B tubes? A year or so ago I contacted them and they were really pricey per tube. A lot more than other reliable tube sellers like Upscale or even Parts Connexion.

Thanks and advise when you can.