Transmogri-Notes Edition 3:

Tube Bias Modulation Tremolo

In this edition a few simulations are performed to explore the differences in effect
of a vacuum tube tremolo in which the amplitude modulation is achieved by modulating
Power Tube bias

Since I didn't have a power pentode model handy, I opted for the 12AX7 Triode model.
This will leave the question unanswered whether there is a significant difference between
the way the Pentode behaves in these conditions vs the Triode, but I think this does
shed a little light on what makes the salient characteristic of this kind of tremolo.

Below it seems reasonable that a JFET emulation would come close to capturing the
salient characteristic of this kind of gain modulation technique.

The BJT implementation with a controlled current source serves as an interesting
proof of concept to drive a somewhat different kind of tremolo or discreet comoponent
compressor design.

Tremolo Implemented with 12AX7's

Big-Picture Modulation Shape.

Zoom in on the distortion that appears at max modulation depth

Tremolo Implemented with JFETs

Big-Picture Modulation Shape.

Zoom in on the distortion that appears at max modulation depth

Tremolo Implemented in a Slightly Different Way with BJT's

Big-Picture Modulation Shape.

Interestingly there was no distortion apparent when zoomed into max modulation depth, so there
is nothing interesting to show on the zoom scale