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#1
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What makes a good linear triode?
I've been drawing loadlines for my amp project input triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7 and 12AX7. I notice that the minature B9A valve curves aren't all that evenly spaced, is this somehow related to the geometry needed to cram a dual triode into a small envelope?. Is there such a thing as a nicely linear B9A triode with medium to high gain suitable for an input stage?. Mark Harriss |
#2
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Mark Harriss wrote: I've been drawing loadlines for my amp project input triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7 and 12AX7. I notice that the minature B9A valve curves aren't all that evenly spaced, is this somehow related to the geometry needed to cram a dual triode into a small envelope?. 6CG7 were first developed using exactly the same internals as a 6SN7, and the tube slightly derated for dissipation. The 6CG7 then came out with various mainly smaller plate structures, and just as linear as the octals. 6BQ5 strapped as a triode is also just as linear as anything octal. the 12AX7, 6SL7, 6SN7, 6CG7 are amoungst the most naturally linear devices in the universe, especially when set up as U followers, or loaded with a CCS. Is there such a thing as a nicely linear B9A triode with medium to high gain suitable for an input stage? 12AY7. This is more linear but with similar gain to 12AT7. Higher Ra though. 12AT7, 12AU7 are less linear than the rest, but so what if there is 0.5% thd at 3 vrms output from a typical set up? its only 2H. My fav is NOS 6CG7 from Telefunken, or even Oz made varieties. Linearity is important, but then when you swap tubes in an amp, sometimes you get a sound change. 12AU7 are generally more linear in practice than the curves indicate, and I find its one of the nicest tubes for a line stage, or as an LTP phase inverter in a power amp. Patrick Turner . Mark Harriss |
#3
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Closer electrode spacing tends to reduce linearity. Unfortunately
it also increases Gm, which was the tube designers' holy grail. Hence older, bigger designs do seem to be more linear. As Patrick says, 6CG7 is a good bet in that regard. John "Mark Harriss" wrote in message ... I've been drawing loadlines for my amp project input triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7 and 12AX7. I notice that the minature B9A valve curves aren't all that evenly spaced, is this somehow related to the geometry needed to cram a dual triode into a small envelope?. Is there such a thing as a nicely linear B9A triode with medium to high gain suitable for an input stage?. Mark Harriss |
#4
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You guys ever took a look at the ECC40 curves on a CCS ?? ;-)))
"John Harper" schreef in bericht news:1075232292.917623@sj-nntpcache-3... Closer electrode spacing tends to reduce linearity. Unfortunately it also increases Gm, which was the tube designers' holy grail. Hence older, bigger designs do seem to be more linear. As Patrick says, 6CG7 is a good bet in that regard. John "Mark Harriss" wrote in message ... I've been drawing loadlines for my amp project input triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7 and 12AX7. I notice that the minature B9A valve curves aren't all that evenly spaced, is this somehow related to the geometry needed to cram a dual triode into a small envelope?. Is there such a thing as a nicely linear B9A triode with medium to high gain suitable for an input stage?. Mark Harriss |
#5
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"Ronald" wrote in message
... You guys ever took a look at the ECC40 curves on a CCS ?? ;-))) *Looks at graph* Oooooooo... If it had a vagina I'd be set. ;-) Tim -- "That's for the courts to decide." - Homer Simpson Website @ http://webpages.charter.net/dawill/tmoranwms |
#6
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You guys ever took a look at the ECC40 curves on a CCS
Keep forgetting I have a handful of these I've never used. They do have a good reputation. === Andy Evans === Visit our Website:- http://www.artsandmedia.com Audio, music and health pages and interesting links. |
#7
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Hi Andy ,
Keep forgetting I have a handful of these I've never used. They do have a good reputation. I dicovered this tube by ear and saw the curves after that because I liked the sound . The curves look good almost everywhere but I liked them best at some higher voltage on the plate , 150V or so . A 6SN7 does great on 80V on the plate but you won't hear the best of the ECC40 at that voltage ..... The biggest problem might be the sockets ...... Best regards , Ronald . === Andy Evans === Visit our Website:- http://www.artsandmedia.com Audio, music and health pages and interesting links. |
#8
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"Tim Williams" wrote in message ...
"Ronald" wrote in message ... You guys ever took a look at the ECC40 curves on a CCS ?? ;-))) *Looks at graph* Oooooooo... If it had a vagina I'd be set. ;-) Tim Uhmm.. *blank stare* Whoa.. :-p |
#9
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Hi Ronald,
regarding ECC40: The biggest problem might be the sockets ...... At least for low quantities of either. If you intend to use, say, 2 pcs of ECC40 in a circuit without having both (tubes and sockets), this may be costly. If you have a stash of either, the picture looks more bright ;-) Tom -- If in doubt, mumble. |
#10
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If you intend to use, say, 2 pcs of ECC40 in a circuit without having both
(tubes and sockets), this may be costly. Not really - I buy in holland for these type of valves. No problem with tubes or sockets, plenty of good dealers. === Andy Evans === Visit our Website:- http://www.artsandmedia.com Audio, music and health pages and interesting links. |
#11
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Patrick Turner wrote:
Mark Harriss wrote: I've been drawing loadlines for my amp project input triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7 and 12AX7. I notice that the minature B9A valve curves aren't all that evenly spaced, is this somehow related to the geometry needed to cram a dual triode into a small envelope?. 6CG7 were first developed using exactly the same internals as a 6SN7, and the tube slightly derated for dissipation. The 6CG7 then came out with various mainly smaller plate structures, and just as linear as the octals. 6BQ5 strapped as a triode is also just as linear as anything octal. the 12AX7, 6SL7, 6SN7, 6CG7 are amoungst the most naturally linear devices in the universe, especially when set up as U followers, or loaded with a CCS. Is there such a thing as a nicely linear B9A triode with medium to high gain suitable for an input stage? 12AY7. This is more linear but with similar gain to 12AT7. Higher Ra though. 12AT7, 12AU7 are less linear than the rest, but so what if there is 0.5% thd at 3 vrms output from a typical set up? its only 2H. My fav is NOS 6CG7 from Telefunken, or even Oz made varieties. Linearity is important, but then when you swap tubes in an amp, sometimes you get a sound change. 12AU7 are generally more linear in practice than the curves indicate, and I find its one of the nicest tubes for a line stage, or as an LTP phase inverter in a power amp. Patrick Turner . Mark Harriss Hi Pat, I have some 6SL7 and 6CG7 on order now but I'm also having some good results with a 12AX7 as gain and concertina at the moment: I get a voltage slew of 18 V/uS and it takes a square wave up to 80 KHz with a bit of leading edge rounding off. The gain should be enough to have some feedback as well. About the only Phil in the ointment is the concertina gets a bit out of balance at high frequencies and high levels possibly due to losses in the cathode resistor bypass caps. Regards Mark |
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