To quote you Ralph; 300bs and 6as7gs "sound about the same" "They are both quite linear"
Ralph, I don't understand how you can say that.
The fact is, the 300b is much more linear than the 6as7g. The 6as7g, in a circuit optimized for it, will produce much more harmonic distortion than the 300b, in a circuit optimized for it. (at all power levels)
The plate curves above clearly show this.
BTW, a 300b circlotron built with the same number of triodes (16) will have an output impedance of 16.4 ohms compared to 10 ohms for the M-60. (This is without feedback of any kind.)
Into an 8 ohm load, the 3rd harmonic distortion at 1 watt is .0123% for the 300b and .131% for the 6as7g.
At 5 watts the distortion for the 300b is .0693% and .6172% for the 6as7g.
At 10 watts .1358% and 1.142%
20 watts .2871% and 1.9268%
60 watts 1.1311% and 3.9534%
To be clear, these distortion numbers are for the output stage only.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
