Preamp Deal of the Century

hello Lisbon. The original 6f6 valves[power pentodes] date back to the early 1920's and were actually first produced in all metal form and looked similar to the early 6v6 metal valves that are so common in early guitar amps.Do "not" use these metal types as they do not sound the same. To the best of my knowledge,the 6F6G [Shoulder shaped glass vavles] were produced from the late 20's through to the early 40's. The tube was produced by either Sylvania or National Union and rebranded for many radio companies of the day. Mine say Rogers,however I have also seen them labelled philco,electrohome,RCA,westinghouse etc.There are also quite a few different versions of the 6F6g's with different looking plates and internals.The ones that I am referring to had rounded black plates like the Western Electric 350b.I have seen many with flat black plates as well. I am not sure if I can post a picture on this thread,if you want to see a picture of the internals of this valve,I can e-mail you one off-line. Cheers David.

Hey Bryan.Tell me how you post pictures on this thread?

Photos of the 350b and 6F6G courtesy of Ecclectique!

Photo One showing 350b and 6F6G

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First, the Tung-Sols:

I am not an expert (far from that) on NOS tubes. Started with the stock tubes, then the Sylvanias VT-231 and now (since today!) the Tung-Sols Round Plates. The Sylvanias were airy (nice) but sounded lean and clinical in my Chardonnay. Actually, not too different from the stock tubes. But quite more expensive and microphonic. Sold them. With the Tung-Sols I had a very bad start while ago. Once I put them on the preamp they started to make some "huuummm...". When I got near them the "huuummm..." turned out to be a much louder "HUUUMMM...". Ouch! Well, I gave them a couple of minutes to settle down and the noise disapeared almost completely (!) As for the sound, it is quite the opposite of the Syls. A bit less airy (can I "fix" that with the 6F6G?...) but everything else was much better. Natural highs and lows and a palpable midrange. This is a very musical, very emotional tube. I guess I am done with 6SN7 type.

Now the 6F6G:

First of all, THANK YOU Eccletique and Bwhite! I guess I can get a pair of Sylvania Green base print 6F6G tubes. But I must confess that after my experience with the Syls VT-231 - regading sonics AND specially microphonics - I do not feel very confortable to go again with the Syls... So I ask: are these really good? How do they behave as for tight bass / sweet highs / air AND microphonics (comparing to the stock KT-66)?

Thanks guys!
Lisbon

Lisbon, The regulator tubes (6L6/6F6/KT66,etc.) will not increase the microphonics at all.