g this dynamically it is possible to change a given clock frequency by only a small percentages.

With this circuit it is possible to generate a test audio signal compatible with ELA-systems for 100 Volts. ELA here means Elektrische Lautsprecher Anlagen which is the german name for public address loudspeakers focussing on speech.

Any waveform is possible using appropriate mathematical methods for compensating the losses and distortion intruduced by the amp and the transformer:

The primary sound is first generated with Steinberg Wavelab as an ordinary PCM stereo signal at 24 bit / 96 kHz. The 1000mV signal from the sound card's RCA jacks is then converted to 100mV by calibrated analog amplification with a third-party KEMO AMP module and linear equalization with a VST equalizer chain in Wavelab to compensate the transformer's high frequency attenuation and level limiting behavior. The transformer is factory rated for 220V and therefore operates here in a largely linear range. However, some distortion may still occur at higher voltages due to magnetic saturation effects. Therefore, a non-linear pre-distortion method is used to mitigate these problems.

Instead of Wavelab, also my FPGA-based Signal-Synthesizer can be used to drive the circuit.

 See also Test Signal Generator