Hello to everyone, I really enjoy Amir's reviews and appreciate everything he does for the community.
My concerns are that why people make such blanket statements about active devices, certainly most of us should know by now that with enough open loop gain we can achieve fantastic numbers regardless of type of active components. The problem with tube amps is the output transformer typically limits us to <30db of negative feedback which if you take enough care to make the open loop circuit linear enough should be plenty to get very low distortion.
I have looked but I haven't seen one well designed tube amp reviewed here, I think that needs to change in order to show good performance can be had with tubes. For example the original Mullard circuit can get 20 watts output with .05% THD. This is original circuit with zero help from many decades of experience. For example do you see many transistor amps that use resistive loads? No, they use high AC impedance loads like current sources, so load tubes with appropriate high impedance loads and you'll notice a substantial decrease in distortion. Part of the issue I believe is many of the tube companies don't want to spend the time to work out the compensation networks, I test so many tube maps with awful ringing that can be fixed with some simple control theory application.
So how is it here we are in 2022 and tube amp manufacturers are still just copying resistor loaded circuits from the 40's and 50's? I have been lately researching the David Berning circuit for his bridged output impedance converter which removes the worst part about the tube circuit, the output transformer. We still use TWT in space communications so tubes are still top dog in many applications. I'd love to give Amir some amps I have made as they perform FAR better than the majority on the market because I don't copy old designs and I'm just a nobody with a desire to use tubes for no apparent reason other than I like them. I am not saying tubes are better or worse, everything has it's pros/cons but I admit I just use tubes because I find them funner to build with and nothing else. I find it odd a nobody like me with little effort can get much better specs than these amps selling for thousands of dollars where I on average spend $500 for my builds. Must be a pretty huge markup with some of these awful amps on the market giving tubes a bad name.
I eagerly await Amir to get a decent tube amp to measure to put the whole "tubes make distortion" myth to rest, to me it's more tube makers are afraid of feedback for some reason and that's the downfall not the fact they use tubes.