Recommend 300b tubes for Frankenstein Amps

Are you sure the tubes are at fault? You would not want to replace them with expensive tubes only to have that happen again.

The KRs sound wonderful but are not reliable
I didn't get 100 hrs out of one of mine
Try the Black Bottle from Shugung or the Full music 300b/c carbon plates that I am currently using
They sound great with the Franks

Emission Labs 300B-XLS, or if you can adjust the bias and get away with less output try the EML 300B-mesh.

Abill
I have about 500 hours on my Shuguang Treasure Series(Black glass) tubes. They sound wonderful and have been reliable.I got them from Grant Audio for 600.00 per pair, not cheap but I have no complaints. The Frankenstein MK2 amps are top tier and deserve premium tubes. Israel Blume has warned amplifier owners about premature failure with these KR tubes,

Thanks everyone for the responses. I emailed Israel and he also recommends the Black Glass. He said they sound as good as the kR Balloons and are very reliable. He is currently using a pair as we speak.

Hey Abill, I don't want to hijack the thread but how are you liking the Victory IV?

Brf
I've had the Victory IV's for almost a year and I have no desire to get ride of them. I was using them with a well known 300b amp, which I sold. I purchased a Coincident Frankenstein amp and the speakers sound much better . Then I purchased coincident Extreme power cables and rca interconnects and I can't believe how much better everything sounds. Never sounding harsh very well balanced sound from top to bottom.
If you purchase the victory IV's and you don't like the sound it's not the speakers.
I think Coincident is the best value for the dollar !
Israel is always quick to respond to emails.
Hope this helps.

I don't disagree about Coincident's being one of the best values in hi-end. BTW if your system requires more bottom end and dynamics, I really like the EML 300B - XLS, this is the tube I use.

Unusual, unless something wrong with the plate plate voltage or the bias voltage/cathode resistor.It is a circuit problem not the tube.