Even better BJT amp sim... split lines...

[Steben]

Output at 1kHz. The roundness of that graph is probably a bit too much. Although the treble cut helps there.


Uses a bit the same trick as Peavey Transtube T dynamics but without bias shifting of caps.
At the emitter of the last buffers we see these signals with different inputs:


Low signals almost pass the base-emitter junction and added up they give an almost sine wave again.
The higher the signal, the bigger the compression at the first base-emitter junctions (think rangemaster) resulting in half an amplified signal at the collectors and half squashed.
Beyond a certain point there are gaps in the sum of the signals resulting in cross over distortion.
The zener clipping is there to balance the clipping (and softening) point.

Notice the RE in the common emitter stages is different. The transistors have different hFE and this helps to compensate.

[Vivek]

Is all filtering done by input and output caps only ?

[Steben]

Is all filtering done by input and output caps only ?

Yes

[Vivek]

If you send me your LTSPICE file, I can add the code for AC Transfer function and send it back to you