Tube rolling.
Tube rolling , or plugging a different tube into the socket to see how it sounds , is IMHO not really a good way to test tubes.
I think that tubes of a type , say 12AX7 , from different manufacturers are not exactly the same. They belong to the generic same type by the few parameters that we usually mention. That really does not make them exactly the same.
Like the NE5532 debate in another thread. Those from Signetics sound different from those from TI.
So we should have 12AX7 , 12AX-7a , 12AX-7b etc. They are not all the same. So if some type sounds better in the circuit it could be at its best operating point. Maybe if the other passive parts are changed the competing tube might also sound as good if it is at IT's best operating point.
So the comparison 'may' not be correct. So tube rolling can give interesting results but not necessarily conclusive ones.
Tube rolling , or plugging a different tube into the socket to see how it sounds , is IMHO not really a good way to test tubes.
I think that tubes of a type , say 12AX7 , from different manufacturers are not exactly the same. They belong to the generic same type by the few parameters that we usually mention. That really does not make them exactly the same.
Like the NE5532 debate in another thread. Those from Signetics sound different from those from TI.
So we should have 12AX7 , 12AX-7a , 12AX-7b etc. They are not all the same. So if some type sounds better in the circuit it could be at its best operating point. Maybe if the other passive parts are changed the competing tube might also sound as good if it is at IT's best operating point.
So the comparison 'may' not be correct. So tube rolling can give interesting results but not necessarily conclusive ones.