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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
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.
jedinite24's avatar
jedinite24
1,503 posts
 
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.
c1ferrari
464 posts
 
"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."

Interesting...
Anyone else have similar observations?
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.
bigby
159 posts
 
I used to have a lot of trouble with the tubes in my VK-75se. Since cleaning the pins and sockets with Deoxit and letting the amp warm up an hour before using it, I haven't had any problems.
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