Favorite 300B: Sophia vs KR

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

Hi Ian,
Good question,
Takatsuki=95
AVVT 32SL and EML XLS = 90
Shuguang BT=80 still a solidly good tube but for me not to the level of the current production EML XLS.
Sophia RP, been quite awhile but it was very good in the Frankenstein(I`d need to hear it again). This tube has a different character compared to the two european 300b tubes.The RP could be a "touch" better but a very close call. I honestly feel there`d be an amp to amp variation,favoring one over the other.
Charles,