Favorite 300B: Sophia vs KR

Gary,
I don`t believe this is universally true for the 300b.I have EML,AVVT,Shuguang BT and Takatsuki and none of these came with this type of warning/limitation of playing time.
I`ve used them with the amplifier on morning to night without any problems. Sophia Electric may have their own chosen restrictions.
Charles,

I will always have the tuner playing.

Just to be clear. I received no formal, written restrictions from Sophia. It was during a casual conversation with Sue that I received the five hour advise. Most of my friends, who have tube amplifiers, also try to minimize very extended sessions. I thought that this was common understanding. If this is unusual, I would welcome the thoughts of some of our more technically advanced members.

@Watersidedave

Have you talked to Sophia and what's their comment?

It looks like mega failure regarding quality control, can't be any differ.

THX

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.