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RE: Michael, a broader question

The 6CA7 and the EL34 are only identical in the sense of what they present for a load to the circuit they are put in..The EL34 is a Pentode,the 6CA7 is a tetrode.The KT77 is also a tetrode.

I have in my possession,the best of EL34s ever made and I have them in NOS/NIB,and I have many very close to NOS in the ones I run out of the box.What I have found with EL34s,if they are well matched running at the higher GM ranges,they have a much better chance of maintaining their clarity all thru the spectrum.I have also found that you need the most pure.low distortion and linear driver stages to correctly run EL34s.
The 6CA7s are a bit more forgiving by nature being a tetrode IMHO.

"Now I see you specify the 8200 to 8700 range for the 6AC7s. But can you comment on 6AC7s which fall outside that range, are they still better than EL34s or quite similar?"

It depends how far you fall out of that range..Higher GM typically favors lower distortion numbers from my experience. Groove tubes had this rating system that was fantastic.They did their ratings on numbers 2 thru 10.


"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken



Edits: 07/18/16

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