NE555 high voltage flyback driver, modifications for reliability and isolation

[ZosoZeppelin]

How to modify this circuit in order to increase output voltage and increase reliability. Is it possible to connect an AUX cable input into the Control voltage (pin 5) of the 555 timer in order to create musical arcs, if so how to isolate and protect the music player.

 

[dick_freebird]

555 is too weak to drive a big MOSFET well
enough to get good boost. You need snappy
or the slow ramp will eat all your voltage.

Presumably you only need the bass or
maybe sub-kHz envelope following. That
still wants 100kHz - 1MHz switching and
a control loop (or open loop) that can
follow.

There are better modulators than the 555.
I think given the backend, a PFM might
be better, and do an audio-envelope-detect
followed by V-to-f and that f is the trigger
to a pulse-shaped car coil shunt drive (resonant
primary circuit, pulse width comports with
the tolerable volt-seconds of the primary, etc).

There was a Chrysler ignition module that
once was popular, everything but the power
source and a logic level input.