I should add that while I thoroughly respect the CCS in the cathode solution it does have a downside. It may or may not be important to you. You cannot overdrive the final stage in that setup. This is much more important in triode mode. You just can't get an average tube to get close to it's completely "shorted" overdrive condition due to diversion of grid current in the overdrive condition.
If you use a source follower in a triode drive tube you can get up to twice the power out of the tube if it's driven by a source follower. This is a BIG advantage. My understanding is that the Baby Huey is a pentode circuit that acts like a triode in most respects so a source follower advantage would be limited in that amp. But that's a special case.
Edit: I guess I better add that the Baby Huey actually has source followers but they aren't really being used for overdrive. At least if I understand the circuit correctly.
If you use a source follower in a triode drive tube you can get up to twice the power out of the tube if it's driven by a source follower. This is a BIG advantage. My understanding is that the Baby Huey is a pentode circuit that acts like a triode in most respects so a source follower advantage would be limited in that amp. But that's a special case.
Edit: I guess I better add that the Baby Huey actually has source followers but they aren't really being used for overdrive. At least if I understand the circuit correctly.
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http://s33.postimg.org/hrzc56u67/20160527_222840.jpg Here's the final circuit i designed. What do you think, any recommendations?
Are you specifically interested in the pentode sound of the EL84 finals in your circuit? The reason I ask is because they definitely have a sound different from a triode strapped EL84 circuit. They both are valid choices but have a different sound. If you don't know then it's good to try to get to hear one or both topologies from someone near you to see which you prefer. If you prefer the triode sound then I would suggest the Baby Huey rather than reinvent the wheel. If you specifically like the pentode sounds then the topology shown in your circuit is a perfectly valid choice, especially if you are concerned about tube balance as you've indicated. Both the Baby Huey and yours seem to solve that problem but it appears to me they will sound different because of the Baby Huey's unusual feedback circuitry that simulates triode sound.
in my latest repair job on the Fisher 400, it had a common -15v grid bias, so what i did was to put a cathode resistor each and bypassed it with a cap....
disabled the grid supply and connected grid leaks to ground...
so it turns out that two tubes on the right a almost ready to give up...
An externally hosted image should be here but it was not working when we last tested it.
I've heard both triode and pentode modes of the EL84 tubes. I have even made some experiments with ultralinear sound and i gotta say triode mode is a bit mushy for my taste. The pentode mode is considerably louder than the triode mode (i think it has a few extra watts into it) and has a more rough sound. I have no personal preference in which mode they work, just as long as they work correctly. I actually have two identical Output Transformers both central tapped at half the primary. That's how I made my ultralinear experiment. I just wired them in series and tapped at the center tap for the ultralinear mode. It's not exactly 43% but it did sound A HELL LOT BETTER than the pentode counterpart and had quite the same punch, so alternatively i may actually wire it this way and test it out again on the scope.
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It depends on speakers. Some sound better with triodes (high Q), some sound better with pentodes (low Q). Sometimes people prefer even high Q speakers with pentodes because either output transformers are small, or they forgive bumpy frequency response when speakers distort less.
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