I must admit I'm a little bit confused about cathode followers.
Why do they have a reputation of sounding bad, and when do they sound good?
Apart from the obvious (bad design which makes them oscillate at RF etc.), I mean. And apart from loading them too much.
For instance, in phono preamps, you often see a CF between the last voltage gain stage and the volume potentiometer. Or you see them as output stage of a HiFi preamp, to improove cable driving capability.
Which all makes sense from an impedance point of view. And yet they are frowned upon by many "High End" audio builders. Is there a known technical reason for that?
And if so, does it also apply to the WCF, or to CF with current source loading? I've seen one circuit that uses a transitor constant current source, and a transistor emitter follower to feed the CF's output signal to the anode, to have the CF tube working with both, constant current and constant voltage. Constant current only for small load currents, though: Which makes me wonder if I need a CF then, at all ...
But really, at the heart of it, I don't understand the mechanism that would make a CF sound bad at all.
Can someone enlighten me?
(If it's been discussed before - and I suppose it has - just point me there.)
Thanks,
JH.
Why do they have a reputation of sounding bad, and when do they sound good?
Apart from the obvious (bad design which makes them oscillate at RF etc.), I mean. And apart from loading them too much.
For instance, in phono preamps, you often see a CF between the last voltage gain stage and the volume potentiometer. Or you see them as output stage of a HiFi preamp, to improove cable driving capability.
Which all makes sense from an impedance point of view. And yet they are frowned upon by many "High End" audio builders. Is there a known technical reason for that?
And if so, does it also apply to the WCF, or to CF with current source loading? I've seen one circuit that uses a transitor constant current source, and a transistor emitter follower to feed the CF's output signal to the anode, to have the CF tube working with both, constant current and constant voltage. Constant current only for small load currents, though: Which makes me wonder if I need a CF then, at all ...
But really, at the heart of it, I don't understand the mechanism that would make a CF sound bad at all.
Can someone enlighten me?
(If it's been discussed before - and I suppose it has - just point me there.)
Thanks,
JH.