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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

Showing 2 responses by btselect

btselect
26 posts
 
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.
btselect
26 posts
 
Jedinite24,

I got them from a small local dealer who got them from New Sensor, in the past whenever a group of us were in need of tubes we made a bulk purchase to get a lower price. I've haven't bought these tubes in a while, I have bought hundreds of these tubes in matched pairs, the price of these tubes back then was very cheap. I would check if Jim McShane sells these tubes, I believe he sells tubes from New Sensor, or anybody else who sells tubes from them should be able to help you. Like on ebay, the sellers there are selling a lot of tubes so they can buy tubes from New Sensor in bulk getting a much lower price, and passing the savings to the general public.
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