| Re: mmmmmm.... [message #30810 is a reply to message #30809] |
Fri, 04 March 2005 05:57   |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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Time always moves faster as you get older...that and I am going to have to start working full time for somebody at some point...
regards,
Douglas
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| Input stage [message #30822 is a reply to message #30801] |
Fri, 04 March 2005 13:33 |
cheetah
Messages: 70
Registered: May 2009
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Viscount |
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Douglas, Have you considered using a pentode diff amp on the input, instead of a cascode diff amp. Pleanty of gain, good drive capability, much less complexity compared to the cascode. Joe
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| Re: Input stage [message #30825 is a reply to message #30822] |
Fri, 04 March 2005 13:41 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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Hey-Hey!!!,
Yes I have. Built with 6AK5, 6AU6, 12BY7, 12GN7, 6AH6, 8136. Missed a few, but the slightly more complex looking cascode works better. Tread Ec2 like the pentode's g2, and you're off. the g2 being in parallel with the plate does funny thigs( I think ) to the constant current out of the cathode circuit. The cascode is a series afair, and the pentode is a parallel. You still need a good g2 supply...
regards,
Douglas
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| Re: Input stage [message #30827 is a reply to message #30825] |
Fri, 04 March 2005 13:46 |
cheetah
Messages: 70
Registered: May 2009
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Viscount |
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So cascoded 5687's e-linear connected to the outout stage sounds like a winner. By the way, what kind of input/driver stages are you planning to drive a brute like the 813? Joe
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| Re: Input stage [message #30831 is a reply to message #30827] |
Fri, 04 March 2005 19:19 |
PakProtector
Messages: 935
Registered: May 2009
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Illuminati (2nd Degree) |
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Hey-Hey!!!,
there is no big deal with a pentode rigged 813. g1-everything else is not too bad, less than 30 pF. A 2A3 grid has more than 60 pF. Not too bad a drive proposition when you get right down to it. A 6SN7 would be enough...but for appearances sake, a proper DH transmitting valve ought to be used. There are a few cool ones, some with tantalum plates which glow a dull orange. Thoriated tungsten filaments. Must have its appearance done correctly. 866's in the PS of course. Two pairs of 'em most likely, or perhaps 866's and 816's.
regards,
Douglas
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