Posted by Tnuctipun [ 64.12.116.65 ] on April 09, 2005 at 11:58:02:
In Reply to: Re: amp input stage posted by manualblock on April 09, 2005 at 07:49:35:
Well, the pre that can drive anything is right beside the perfect amp...
At a more practical limit, we have Guinevere.
Merlin is fairly high input Z, basically as set by the grid leak of the driven triode. I think I drew this at 100k, but 47k resistor would be a good suggestion, and less might be even better. The cascode shields the grid in a similar way the screen grid in a pentode does, so we don't have a triode's Cg-a multiplied by Miller capacitance.
I take Wayne's mention of noise resistance as important. If we're going to drive Merlin with a pre like Guinevere, we can probably cut the input grid leak resistor to 20k or less w/o troubles. I am going to get out the Iron and try some of this on my amp as soon as I can.
regards,
Douglas
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