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The 5E6P is the same as my 5E5P only with more or less military ambitions and with congenital “western” pins layout. It has more fragile specifications and more tight tolerance then 5E6P but it is the very same tube. There is very very very minor sonic difference between then and it is why I used 5E6P for my MF and tweeter channel. Still, the 5E6P and 5E5P has the same character in sound and might be consider as the same tube.

However, the 5E6P has the identical pins lowing with another my favorite tube – the 7721 or D3a in European specification:

http://www.goodsoundclub.com/pdf/7721_D3a.pdf

The 7721 is from the same family as my beloved 7788 and they were made in the truly golden age of tube manufacturing. It is a bit more powerful then 7788 and it is much better driver then 7788. The 7788 is a king for microphones and MC cartridges, the 7721 is a next output state…

Now is the fan…. The 7721 and 5E6P have the same pins and pretty much interchangeable.  The 7721 won’t handle as much power as 5E6P but my interest to use it on tweeters what I need no power.  I drive the 5E6P at 200V and a good 5E6P pushes 1800mS under 30mA and with minus 4V on bias. The 7721 (as a triode) give the same transconductance at the same voltage and 12mA on plate.

What I need to learn how would 7721 sound driving my tweeter.  I also need twice lower plate impudence for my tweeter driver (do not ask why - it is classified). The 7721 does has lower impedance but a higher current. I wonder what would be the 7721’s plate impedance at 12mA.

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