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I have been running my little stereo amp in triode mode lately and really dig the sound, so I thought about trying some actual triodes in there instead. After looking around, I discovered the 6s4. It is a triode which should be almost exactly the same as a trioded 6bq5/el84 as far as bias, plate resistance and output power etc, with a slight socket rewire.
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Last edited by Austin; 09-24-2012, 04:01 AM. -
Not sure if they are that close... If you just want a cheaper version of the EL84, Russian or Chinese 6P14 are pretty cheap too.Originally posted by Austin View Post
Jaz -
I actually kinda like the sound of russian equivalents. Although I remember using some 6N2P's in place of 12ax7's before and getting some horrible distortion... turns out the internal shield had developed some sort of charge on it as I left it floating, but grounding it solved the problem pretty much immediately. I think the main reason pentodes are used instead of triodes for output stages is purely for cost, since you have limited voltage swing with triodes. An output stage built specifically for triodes might turn out to be pretty decent sounding - I imagine it would clip more gracefully too.Comment
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Nice work with stretching one data grid to match the other and ofsetting the colors. Good visual."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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http://www.mif.pg.gda.pl/homepages/f...084/3/300B.pdf
http://www.mif.pg.gda.pl/homepages/f...093/6/6BQ5.pdf
http://www.mif.pg.gda.pl/homepages/f.../127/6/6S4.pdf
Okay so I should be looking for more vertical curves like the 300b then? How about a 6gu7 with both sides in parallel for an output tube? I already have two of them but didn't think of this before.
http://www.mif.pg.gda.pl/homepages/f...135/6/6GU7.pdfComment
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Getting closer... but the plate dissipation is pretty low even with 2 in parallel. Might be worth a try since you already have the tube. Let's know how it turns out.Originally posted by Austin View Post
JazComment
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Well after the last few days, I ike the sound of the 6gu7 better than the 6s4 though they both work fine at -12 or -15 volts and 350 volts plate. The 6s4 seems to have more oomph and the 6gu7 more clarity and fine grained detail. I would love to be able to parallel 4 or more of these per channel I bet it would sound great. I am using combination bias with the 82 ohm cathode resistor and bypass and 9 volt battery in the grid circuit. One problem is it seems to be running up against grid current well before it gets to the cathode potential so an interstage transformer would be great. I get about 1 watt according to my meter with a 8 ohm load and 5 k output transformer with both 6gu7 sides parallel.
Now I get to figure out a use for these 6s4 tubes I have...Comment
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Run the 6s4's parallel to the existing 6gu7's INSTEAD of more 6gu7's.Originally posted by Austin View Post"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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Yes that's a good idea but I am out of space on this chassis. I think I will leave them in there until I can get some new power caps and then ditch the tube regulator and can style capacitor in favor of two octal tube sockets. Then I can use the 6gu7s to drive a 8417 or el34 etc for some real power. They sound good but I miss the power of the pentodes.. Im going to need some better output transformers, all the edcor ones have ul taps that I woukld like to try. Thanks for the replies.Originally posted by Chuck H View PostComment
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I pulled the rectifier tube and used ss diodes instead and in its place I added a 6bx7gt tube in parrallel with the two 6gu7. I think it might be the best it has ever sounded... Every bit as loud as se el84 pentoded.Comment
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Here it says "6s4 is an example of a high perveance triode". Perveance - Wikipedia, the free encyclopedia
But what does perveance really mean?Comment
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