Favorite 300B: Sophia vs KR

Phaelon,

Couple of my thoughts on tubes and specifically 300b's (one of my faves):

I haven't heard of any manufacturers of tubes recommending limited hours but I wouldn't be surprised if they did. 24/7 is around 750 hrs a month or 9000 a year. That's a lot of hours on output tubes. I can imagine a scenario where there are 2 people with identical amps and running the same tubes...the 24/7 guy gets 6 to 9 months on his, the "on often" guy gets years on his.

Another factor is how hard the tube "amp" manufacturer chose to run the tubes in his design. Good to know specs are the voltage and current. I've seen charts on 300b tubes that have said you can run up to 450 volts and up to 80 milliamps BUT NOT BOTH.

Get an amp that runs the tubes near the ragged edge and they won't last as long as compared to an amp running them more conservative.

Onemug,
Good points, I wouldn't advise anyone to use their output tubes 24/7.I do have my amps on 8-12 hours on some days and have had no problems. The 300b is long lasting if not pushed hard by circuit design as you noted.
Regards,

Thanks Onemug, The lack of any response in support of the notion that tubes need to rest hasn’t been lost on me. There are a lot of smart people on Audiogon. I could have taken it wrong, but in the context of our converstation, I came away with the strong impression that I was being advised to give the tubes a rest to avoid overstressing them. Not because they might pop, but because there would be an accumulated effect that could adversely impact longevity.

I second all of Onemug's comments.

The 5 hour recommendation has to be somewhat arbitary, even for the specific Sophia tube, because to the extent that an optimal figure may be definable for any specific tube, the figure will vary depending on its operating conditions in the particular amplifier.

FWIW my own instinct, based purely on instinct, would be to not hesitate to have listening sessions now and then that are significantly longer than that, but on the other hand to not run any tube power amplifier continuously 24/7, or overnight, or when unattended. The concerns being not only the likelihood of shortened lifespan of expensive tubes, but the possibility of secondary amplifier or speaker damage, or even fire, if a short or other fault were to develop.

Best regards,
-- Al

Charles,

I was wondering given your considerable experiance since posting this:

On a very strict scale where 70=solid performance and 100= absolute perfection.In my system I grade the following,
W.E.reissue =70(just did`nt impress vs the others in my amplifier)
BT=85(very good all around)
RP=93(excellent!)
Takatsuki=95 (sublime experience for me)

How would you rate them now adding in tubes you've compared since, (lsuch as the AVVT etc.) like you to use in the Franks.

Ian