Tube Amp Distortion With BJTs

These are really low voltages, and the distortion is asymmetrical.

Yes, it is asymmetrical, but if you want 100% flat frequency response and second harmonic distortion, then you're just going to have to live with the asymmetry. Anyway, how are you're ears going to know whether or not it's asymmetrical? All they're going to know are the there is a 1kHz wave and that there is a 2kHz wave. Third harmonic distortion can be nice and symmetrical, but this is second harmonic. Also, the low voltages can be fixed using a simple amplifier since this is a preamp, or possibly using a higher voltage power supply.

@jason9, First, forget this audiophil bla bla about tubes and transistors amps. Ok? Anyway, you said already to yoianrhodes the right thing about symmetrie! Congrats, cuz symmetrie is the key for understanding already by watching the waveshape on a scope, what kind of harmonics are dominating and this depends mostly from the Class of your amp! Tube amp and transistor amp can have any Class a,b,ab,c,d .... So they all have the same good and bad sides. There is no need to split the world in tubes are good and transistors are bad or wise versa. The wording "second harmonic" is also somehow wrong, cuz its not a single harmonic which matters its always a matter of ODD or EVEN harmonics. So fundamental, 2,4,6,8,... for even harmonics and Fundamental,3,5,7,9,... and this can be see from its transfer function and its symmetrie! Hope this helps.

This will never sound like a tube amplifier...