Do you know why so many designers use 6sn7 driver for 300B and even 211 and 845 tubes?
1. Do they want to achieve a special slow signature of an amplifier sound?
2. Do they do it as result of lack of knowledge and experience?
@alexberger
To the first, no. I've yet to ask any designers of amps using those tubes why they made any of the choices they did.
To the second, no. You have a different set of issues with the tubes you mentioned- getting bandwidth in an SET of the power levels these tubes are capable of is increasingly more difficult for the output transformer as the power level is increased. I could see that lack of bandwidth being construed as 'slow'.
To the third, no.
You can get good bandwidth with a 6SN7 and you can get low distortion owing to good linearity. So it can be quite neutral, and has the advantage of being capable of fairly high current, so you can drive a fairly high capacitance grid with it no worries. The grids of the power tubes you mentioned would be a walk in the park for this tube. Since its designed for audio, its easier to find lower microphonic examples than it is to do so for something like a 6922 or other frame-grid triodes. A further advantage is that its in production and easy to get. Its also pretty reliable.
