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In Reply to: here we go again... posted by Allen Wright on January 4, 2005 at 04:24:51:
>> The tube amp designers bible, Valley & Wallmann's "Vacuum Tube Amplifiers" goes into CF's in quite some detail, and focusses on how to make them linear WHEN DRIVING CURRENT into a load - and this is where I first read about the advantages of CCS loading and bootstrapping them. >>Allen,
Valley and Wallmann is great if you're designing a RADAR. Not so useful if you're trying to make a practical audio amplifier. Yes, I own it.
No one is arguing that feedback and current sources do not make cathode followers more linear. That's undoubtedly true. I was merely responding to your brash taunt that all non-ccs'd cathode followers are "miss piggies" and don't belong anywhere in audio. That's a silly statement.And declaring that because several tube scopes use CF's with current sources, and thus they are the only correct way to use a CF in an audio application shows a lack of understanding of the fundemental differences between the two tasks, and the limitations inherent in audio to begin with (we won't even go into speaker distortion).
I find it amusing to note that you find a "plain jane" cathode follower repulsive, tweaking them for more gain, bandwidth, and linearity, and yet you seem to be fine with using output transformers!
Bleccch! Talk about limited...
Follow Ups:
I must side with Allen. EVERY CF I have built sounds better with CCS HANDS DOWN!
And if you haven't tried bootstrapping them -you have another treat coming, perhaps even bigger than the CCS. But the bootstrap has to be a tube...
My new years resolution...Regards
Robert Morin
DIY is the only path to audio salvation
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