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Swap 6B4G for 6SL7 SRPP ?

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This would be in a 300B amp. I looked and it seems the largest problem in doing it is the 6.3 amperage. The big question is if it would sound good. I bought a few 6B4Gs a few years back and I have seen things like a 300B in front of a 211 or 845 which makes perfect sense, but putting a 2A3 in as a driver for a 300B power tube............a bit of over kill, but I kind of like the idea.
Now, tell me how it will work, or not work, if you like the idea or anything else. BTW I stupidly bought some of those Syl Jan 6B4Gs which is the size of a Syl 6L6 GC. They can be the tubes for testing it the 1st time.
 

Parafeed813

Member
2012-08-15 8:24 am
It certainly can be beneficial to have some driving power to battle the Miller capacitance of the 300B. If the result will be good depends on the implementation...
'Traditionally', an interstage transformer would be used between the 6B4 and the 300B.
Other options would be a choke, resistor or CCS feeding the 6B4 and a coupling cap to the grid of the 300B.
Tubelab George has a CCS loaded 45 (power)driving his 845 on his site. That could be a start schematic.
One of the most impressive SE amps I have heard used a 2A3, RC coupled to two (PSE) 300Bs.
One important thing to consider is the low mu: you will need an additional stage to get a reasonable input sensitivity. I'd say something like a 6J5/half of an 6SN7 - 6B4 - 300B.
 
I really don't want to be putting more tubes on the chassis. I do have some room under it though, but the low mu is something I didn't even consider.
Two stage amp with 6b4g-300b is possible, but, in best case, it will be a power buffer (you send 1V RMS to input, and has around 0,9V...1,1V RMS at the output). So, a preamp, or additional input stage is obligatory. I like an idea of 6b4g as a driver to 211 or 845, but first stage before 6b4g must have Ku around 80 voltage amplification.
 
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