Question For Owners Of Coincident Frankenstein Monoblocks

I miss Charles1dad’s active participation in this forum. Charles owns the MKII version, as do I. My amps are almost 10 years old now and they seem to get even better as they age. The MKII uses 6EM7 tubes. Israel Blume told me that swapping 6EM7 tubes makes the least difference in sound quality among the tubes used in the Frankenstein. In fact, he supplied me with two different brands and said it would not matter if I mixed them, a different one in each amp. Perhaps the 6SL7’s are similar? I would ask Mr. Blume about them if you haven’t already.
 

As for longevity of 300B’s in the Franks, I have been using the same pair of EML 300B XLS tubes for 9 years and they still sound fine. I listen most days of the week, oftentimes four hours or more a day. 

Thaluza, thank you form your thoughts. and good news regarding the longevity of the 300B tubes in the franks. I too miss charles contributions, especially in my current situation. My MK V version uses one 6sL7 in each amplifier, along with one 5u4. I did ask Israel about swapping them out for high quality NOS tubes and whether that would yield any significant improvement. He was somewhat non-committal, saying only, "possibly". 

That’s not very encouraging, as swapping out both pairs would be decidedly expensive. 

@nightfall Saw your thread on 300B tubes and responded. Don't believe Charles on the forums anymore, in any case he had issues with previous production Elrogs and Takatsukis,  He went to EML XLS, last time I heard he had no issues over many years with these. Based on his and other's experiences, the Franks, at least earlier production versions run pretty hot on plate voltages so have to be careful with 300B selected. As I mentioned in other thread I've had issues with now 2 new production WE so I'd stay away. I believe the Psvane Acme may be a great match and value for the Franks, as mentioned in other thread I've run these well over 1,000 hours without issue in my mono blocks. 

By the way, I own Coicident Statement pre and Turbo 845. The Statement was eating through 101D tubes voraciously until I modified heater voltage with different value and much tighter spec heater circuit resistor. I suspect Israel runs tubes pretty hard in order to get his preferred sound quality, today's tubes may not be up to task. He did modify the latest Statement to run on 300B tubes, perhaps new production 300B up to the task in pre where they don't need to be run as hard.

Don’t have monoblocks, but have the Frankenstein stereo. Does the sound change by changing out the 6SL7’s? Absolutely. I am not a Mullard "need more warmth" guy though, I am a Telefunken "give me more detail" guy. 

I picked up a set of Tung Sol VT229’s, and a set of Sylvania JAN WGT’s. Either improves on the supplied $30 ones. Israel knows darn well the amp can sound better with better tubes, but I understand he doesn’t want to get into tube options with customers. He had a hard enough time answering my questions about which 300B to try, and those are readily plentiful. How can someone recommend a tube that is in short supply, and may cost hundreds of dollars? And then someone buys a bad set from ebay? It is system based. Maybe someone buys the Sylvania’s I have and then complains the amplifier is too bright? It is not the amp’s fault. But you definitely don’t want these if you are looking for warmth. 

Really feeling the need to try Takatsuki’s, but other things to do first.